WO2024252009A1

WO2024252009A1 - Modulation of global regulatory mechanisms and biosynthetic gene clusters for simplified production of natural products

Info

Publication number: WO2024252009A1
Application number: PCT/EP2024/065835
Authority: WO
Inventors: Helge Bode; Paushali CHAUDHURY; Edna BODE; Timo OBERMEIER; Alexander RILL
Original assignee: Max Planck Gesellschaft zur Foerderung der Wissenschaften
Current assignee: Max Planck Gesellschaft zur Foerderung der Wissenschaften
Priority date: 2023-06-08
Filing date: 2024-06-07
Publication date: 2024-12-12
Anticipated expiration: 2025-12-08

Abstract

The present invention relates to a method for finding global regulators in order to induce or increase production of target secondary metabolites. The method comprises providing a bacterium indicator strain producing two fluorescent reporter signals under the same control of two different biosynthetic gene clusters (BGC), preferably highly expressed BGC, performing random mutagenesis in said bacterium indicator strain, and selecting mutant bacteria not producing said reporter signals. The invention also relates to a method to activate the production of target secondary metabolites, and to a CRISPR/Cas based single plasmid to delete or inactivate a global regulator and/or activate a BGC. Finally, the inventive method can be performed in high-throughput format allowing to speed-up the procedure.

Description

Modulation of global regulatory mechanisms and biosynthetic gene clusters for simplified production of natural products Specification The present invention relates to a method for finding global regulators in order to induce or increase production of target secondary metabolites. The method comprises providing a bacterium indicator strain producing two fluorescent reporter signals under the same control of two different biosynthetic gene clusters (BGC), preferably highly expressed BGC, performing random mutagenesis in said bacterium indicator strain, and selecting mutant bacteria not producing said reporter signals. The invention also relates to a method to activate the production of target secondary metabolites, and to a CRISPR/Cas based single plasmid to delete or inactivate a global regulator and/or to activate a BGC. Finally, the inventive method can be performed in high-throughput format allowing to speed-up the procedure. Background of the invention Numerous medicines are directly originated or are inspired from bacterial natural products and their secondary metabolites. These secondary metabolites are known to be produced by bacteria in response to environmental stress or interaction with host, providing competitive advantages. Proteins essential for the production of the bioactive compound are usually encoded by large cryptic gene clusters that remain silent under normal laboratory conditions, which hinders the discovery of new secondary metabolites. The corresponding biosynthetic gene cluster (BGC) can be identified biometric and act as an indicator or marker of bacterial capacity for the production of secondary metabolites. In general, cryptic BGCs are essentially present 5 - 10 times more than expressed BGCs, so that all bacterial genomes contain many more BGCs than there are secondary metabolites known from that particular strain. Understanding the modality of expression of these BGCs will not only allow discovery of new beneficial compounds but also revealing pathogenic mechanisms. The recognition of the global regulators controlling silent biosynthetic gene clusters can help to achieve these goals. In contrast to pathway-specific regulators which control the transcription of a small number of genes, global regulators control hundreds of genes.

GAR-P04397WO09 Application (final)2.docx Activation/inactivation of global regulators is related to significant changes in the production of secondary metabolites and to the induction of corresponding biosynthetic gene clusters. For example, global regulatory mechanisms dramatically affect the production of almost all secondary metabolites (SM, also called natural products (NPs)), in bacteria such as those of the genera Photorhabdus and Xenorhabdus. Several BGCs are silent under the conditions used in laboratories for growing bacterial or fungi strain, or the secondary metabolites are only produced in very minute amounts. Since these secondary metabolites might have interesting biological activities acting as antibiotics, anti-cancer or immune suppressive drugs with applications in medicine, biotechnology and agriculture, it would be desirable to speed-up access to these secondary metabolites. International patent application WO 2019192281 refers to a method for mining secondary metabolism strong promoter based on Streptomyces transcriptome, and application thereof. Taking the strong promoter ermE*p as a reference, using the egfp reporter gene to characterize the activity of the ultimate promoters, and confirm the relatively high activity of the promoter in secondary metabolism. Using high-expression Streptomyces natamycin pathway specific positive regulation factors of the promoters obtained by screening increases the natamycin yield. U.S. patent application US 2016348097 discloses compositions and methods for activating a silent gene or gene cluster with a bacteriophage and/or Streptomyces Antibiotic Regulatory Protein (SARP) transcription factor. Park Jimin et al. (ACS Synthetic Biology, 2021, 10 (8), pp. 1859-73) report on a high-throughput transcriptional characterization of regulatory sequences from bacterial biosynthetic gene clusters (BGCs). In the publication a cell-free expression platform for rapid characterization of regulatory sequence activities in S. albidoflavus is described. Xiang et al. (Communications Biology, 2022, 5 (1), p.901) report on a visualization reporter system for characterizing antibiotic biosynthetic gene clusters expression with high-sensitivity. A visualization reporter system based on Gram-negative bacterial acyl-homoserine lactone quorum-sensing (VRS-bAHL) is also disclosed. The authors showed that VRS-bAHL can be

GAR-P04397WO09 Application (final)2.docx widely used for characterizing gene expression in Streptomyces. With the guidance of VRS-bAHL, a novel oxazolomycin derivatives is discovered. Jingjing et al. (Journal of Biological Chemistry, 2017, 292 (48), pp. 19708- 20) report on a double-reporter-guided targeted activation of the oxytetracycline silent gene cluster in Streptomyces rimosus M527. In Streptomyces rimosus M527, the oxytetracycline (OTC) biosynthetic gene cluster is not expressed under laboratory conditions. The authors used a reported-guided mutant selection (RGMS) procedure to activate the cluster and to obtain a working mutant M527-pAGT-R7. The authors could show that OTC gene cluster was successfully activated using the RGMS method. At the present a robust and efficient method to find global regulators in bacteria such as bacteria and fungi, and for producing secondary metabolites at high levels is missing. This is particular relevant for the bacteria Photorhabdus and Xenorhabdus. It is the objective of the present invention to provide a method for screening for global regulator genes that can be manipulated to activate biosynthetic gene clusters (BGC) for producing target secondary metabolites at high level and / or inhibit background production of other not relevant metabolites. Thus, the present invention further comprises a method to elicit production of a secondary metabolite from a BGC based on deleting a global regulator and / or activating a BGC or based on activating a BGC and / or deleting a global regulator. Importantly, the present invention provides a recombination single plasmid for CRISPR/Cas based gene editing that allows efficient gene deletion and replacement. The objective of the present invention is solved by the teaching of the independent claims. Further advantageous features, aspects and details of the invention are evident from the dependent claims, the description, the figures, and the examples of the present application. Brief description of the invention The present invention relates to a method for finding global regulators in order to induce or increase production of target secondary metabolites. The method comprises providing a bacterium indicator strain producing two fluorescent reporter signals under the same control of two different biosynthetic gene clusters (BGC), preferably highly expressed BGC; performing random mutagenesis in said

GAR-P04397WO09 Application (final)2.docx bacterium indicator strain, and selecting mutant bacteria not producing said reporter signals. The invention also relates to a method to activate the production of target secondary metabolites, and to a CRISPR/Cas based single plasmid for gene editing to delete or inactivate a global regulator, to activate one or more BGC, to substitute a BGC with a fluorescent reporter, or for refactoring. Finally, the method can be performed in high-throughput format allowing to speed-up the procedure. Therefore, the present invention provides a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first BGC and of the second BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein the replacing of step a) and b) is in frame; wherein said GR gene regulates production of a target secondary metabolite. In a preferred embodiment, the method for screening for a global regulator (GR) gene in a bacterium, the method comprises: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene;

GAR-P04397WO09 Application (final)2.docx b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite. In a preferred embodiment, the method for screening for a global regulator (GR) gene in a bacterium, the method comprises: a) replacing a gene sequence of a first highly expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second highly expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d);

GAR-P04397WO09 Application (final)2.docx h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first highly expressed BGC and of the second highly expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite. Reworded, the inventice method for screening for a global regulator (GR) gene in a bacterium, the method comprises: a) replacing a gene sequence of a first biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first BGC and of the second BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, and wherein the first BGC and the second BGC are no cryptic BGCs. In a preferred embodiment of the above inventive method, the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging.

GAR-P04397WO09 Application (final)2.docx In a more preferred embodiment of the invention, the method further comprises after step h), the following step i): i) screening for production of secondary metabolites by HPLC / mass spectrometry analysis. In a more preferred embodiment of the invention, the method further comprises after step h), the following step i): i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis. In a further preferred embodiment of the above inventive method, performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis. In a further more preferred embodiment of the above inventive method, said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non- ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP). In a still more preferred embodiment of the above inventive method, the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug, and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives. In a preferred embodiment of the above inventive method, the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces. In a preferred embodiment of the above inventive method, the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus. In a preferred embodiment of the above inventive method, the bacterium is not Streptomyces. In a preferred embodiment of the above inventive method, the steps a) and b) are performed introducing in said bacterium a Cas gene and a first and second BGC

GAR-P04397WO09 Application (final)2.docx specific crRNA array, a first and second fluorescent reporter gene, a first and second pair of BGC specific homology regions left and right. In a preferred embodiment of the above inventive method, steps a) to e) are performed culturing and handling the bacteria in microtiter plates. In a preferred embodiment of the above inventive method, steps a) to e) are performed using an automated liquid handling robotics, and wherein said robotics enables high-throughput manipulation of liquid added to or removed from cultures comprising the bacteria. The invention also relates to a method to elicit production of a secondary metabolite from a BGC in a bacterium, wherein the method comprises the following steps: i) deleting a GR gene in said bacterium, and ii) optionally activating a BGC in said bacterium; or wherein the method comprises the following steps: i') essentially activating a BGC in said bacterium, and ii') optionally deleting a GR gene in said bacterium; and the method further comprises: iii) expressing in said bacterium at least one positive selectable marker gene and at least one negative selectable marker gene; wherein deleting a GR gene of steps i) or ii’) comprises introducing in said bacterium at least one GR specific siRNA, or a group of sequences comprising a Cas gene, at least one GR specific crRNA array, a pair of GR specific homology regions left and right; and/or wherein activating a BGC of steps ii) or i') comprises introducing in said bacterium a group of sequences comprising a Cas gene, at least one BGC specific crRNA array, a pair of BGC specific homology regions left and right, a promoter system, and optionally an enhancer sequence. In other words, the invention also relates to a method to elicit production of a secondary metabolite by a bacterium, wherein the method comprises the following steps: i) deleting a global regulator (GR) gene in said bacterium, and ii) optionally activating a biosynthetic gene cluster (BGC) involved in production of said secondary metabolite in said bacterium; or wherein the method comprises the following steps: i') essentially activating a biosynthetic gene cluster (BGC) involved in production of said secondary metabolite in said bacterium, and

GAR-P04397WO09 Application (final)2.docx ii') optionally deleting a GR gene in said bacterium; and the method further comprises: iii) expressing in said bacterium at least one positive selectable marker gene and at least one negative selectable marker gene; wherein deleting a GR gene of steps i) or ii') comprises introducing in said bacterium at least one GR specific siRNA, or a group of sequences comprising a Cas gene, at least one GR specific crRNA array, a pair of GR specific homology regions left and right; and/or wherein activating a BGC of steps ii) or i') comprises introducing in said bacterium a group of sequences comprising a Cas gene, at least one BGC specific crRNA array, a pair of BGC specific homology regions left and right, a promoter system, and optionally an enhancer sequence. In a preferred embodiment of the the above method to elicit production of a secondary metabolite from a BGC in a bacterium, the GR gene is cyaA gene. In a further preferred embodiment of the the above method to elicit production of a secondary metabolite from a BGC in a bacterium, the BGC is xenoamicin. In a preferred embodiment of the above method to elicit production of a secondary metabolite from a BGC in a bacterium, deleting a GR gene of steps i) or ii’) comprises introducing in said bacterium at least one group of sequences comprising a Cas gene, at least one GR specific crRNA array, a pair of GR specific homology regions left and right. In a further preferred embodiment of the method to elicit production of a secondary metabolite from a BGC in a bacterium, the Cas is selected from the group comprising Cas9, Cas12 and Cas13. In a more preferred embodiment of the method to elicit production of a secondary metabolite from a BGC in a bacterium, step ii) or step i') comprises activating at least 2 BGCs in said bacterium. In a still more preferred embodiment of the method to elicit production of a secondary metabolite from a BGC in a bacterium, said BGC is selected from the group comprising puromycin, madumycin II, xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives.

GAR-P04397WO09 Application (final)2.docx In other words, in a still more preferred embodiment of the method to elicit production of a secondary metabolite from a BGC in a bacterium, said secondary metabolite is selected from the group comprising puromycin, madumycin II, xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives. In a preferred embodiment, the method further comprises culturing and handling the bacteria in microtiter plates. In a further preferred embodiment, the step i) - iii) are performed using an automated liquid handling robotics, and wherein said robotics enables high-throughput manipulation of liquid added to or removed from cultures comprising the bacteria. Finally, the present invention provides a recombination single-plasmid to activate or silence a BGC in a bacterium by CRISPR/Cas-mediated homology-directed repair, the plasmid comprising: an origin of transfer sequence (oriT), a cas gene under control of a first inducible promoter, genes for a suitable recombinase system under control of a second inducible promoter, at least one positive selectable marker gene, at least one negative selectable marker gene, a crRNA system selected from the group consisting of: I) a crRNA system to activate a BGC comprising: at least one crRNA framework, at least one target spacer specific for a genome sequence positioned upstream to a BGC gene, homology region left complementary to a genome sequence positioned upstream to said BGC gene, homology region right complementary to a genome sequence positioned inside said BGC gene, and a promoter system positioned between said homology region left and said homology region right, and optionally an enhancer sequence; II) a crRNA system to silence a BGC or to delete or inactivate a GR comprising: at least one crRNA framework, at least one target spacer specific for a genome sequence positioned inside a BGC gene or inside said GR, GAR-P04397WO09 Application (final)2.docx homology region left complementary to a genome sequence positioned upstream said BGC gene or said GR, homology region right complementary to a genome sequence positioned downstream said BGC gene or said GR, and optionally a fluorescent reporter gene positioned between said homology region left and said homology region right. In a particular embodiment of the recombinant plasmid, the Cas is selected from the group comprising Cas9, Cas12, Cas13, dCas9. Description of the invention The inventors have here developed a method to finding global regulators to increase secondary metabolite production. The method is based on replacement of at least two constitutively expressed biosynthetic gene clusters by two different fluorescent reporters, followed by random mutagenesis and analysis for loss of fluorescence for both reporters (Figure 1). BGC expression can be analysed by using fluorescence microscopy or FACS. Thus, the disclosed method comprises random mutagenesis, e.g. transposon mutagenesis, screening for loss of fluorescence and mass spectrometry analysis to detect all secondary metabolites. The disclosed method can also be performed in high-throughput in 96-well format or higher (Figure 16A-C), allowing replacement of up to 96 BGCs or more in parallel. The disclosed method allows direct bioactivity testing from crude extracts or simplified isolation of the secondary metabolites. The inventors have also developed a single and easy to assemble vector to apply CRISPR/Cas (Figures 1B, 3A-B, 6A-C) to generate bacterial indicator strains that express a fluorescent protein, for example mNeonGreen, in replacement for a biosynthetic gene cluster (Figure 17A-B) under the same control of said BGC. When global regulatory mechanisms are modified to shut-off global SM production, and then a biosynthetic gene clusters (BGC) for the production of a desired SM is selectively activated, only a single SM class is produced at high level, as showed by the activation of rupshomicin BGC in mutants with deletion of the hfq gene encoding a global regulator (strains V-IX in Figure 12). This is of GAR-P04397WO09 Application (final)2.docx particular advantage to elicit or increase production of a SM from a silent or lowly- expressed BGC. The developed CRISPR/Cas single-plasmid can also be used to delete or inactivate a global regulator or part of it (Figures 1D, 3B) , or to activate BGC expression by promoter exchange (Figures1C, 1D, 3B, 6A-C, 7, 8, 9). Genome editing can be checked by PCR on isolated colonies (Figure 5). Therefore, the present invention also provides a method to elicit production of a secondary metabolite from a BGC based on deleting a global regulator and / or activating a BGC or based on activating a BGC and / or deleting a global regulator, by using the described CRISPR/Cas single-plasmid (Figure 3A-B). Refactoring of mxn BGC (Example 5) led to a substantial increase in the production titer of madumycin to approximately 250 mg/l (Figure 8 B, C and D, Figure 9). Refactoring of xsc BGC (Example 6, Figure 10) allowed reaching safracin B production titers above 150 mg/l. Remarkably, the safracin B amount of the Xenorhadus sp. TS4 strain harboring a single-plasmid for xsc BGC activation was 14 times higher than that of E. coli strain LZ84 harboring the xsc Cluster encoded on three expression plasmids (Figure 11 B). Importantly, the inventive method for refactoring allowed discovering a novel BGC named rpmA-O, producing the compounds 19 - 26, wherein 26 is the primary product named rupshomycin. Compounds 19 - 26 (Figures 12, 13, 14) are not described in the prior art. Therefore, the inventive method has the advantage over the prior art to speed-up access to SM normally produced in very minute amounts, and /or from silent BCG, which is particularly relevant for SMs acting as antibiotics, anti-cancer or immune suppressive drugs. Moreover, the inventive method allows production of several secondary metabolites by a single bacterial multi-producer strain wherein at least 2 BGC are activated by promoter exchange and/or refactoring (Example 13). Such multi- producer strains (or extracts derived thereof) have the advantage of being easier GAR-P04397WO09 Application (final)2.docx to handle compared to culture of several mono-producing strains or handling of many extracts of individual compounds to be combined. The inventive method also allows direct bioactivity testing from crude extracts or simplified isolation of SMs that can also be achieved in high-throughput in 96-well format or higher. Deletion of crucial global regulators allows a much “cleaner” production of desired SM due to the lack of production of interfering SMs. The inventive CRISPR/Cas single plasmid allows multiple rounds of gene cluster optimization, that is especially important for multiple transcriptional units, such as for mxn (Figures 8, 9), xsc (Figure 10) or rpm (Figure 12, 13) BGCs. The inventive CRISPR/Cas single plasmid also allows direct conjugation of the plasmid from E. coli to the recipient strain without any integration of the plasmid or its parts into the genome. Importantly, the developed inventive CRISPR/Cpf1 single plasmid allows transformation of Photorhabdus and Xenorhabdus, wherein Photorhabdus had poor transformation efficiency and Xenorhabdus was not transformable at all with the prior art methods (Example 3). Global regulators and global regulatory mechanisms that affect natural product biosynthesis can be transcription factors (TF), chaperones, metabolic switches, signalling compounds binding to TFs. Exemplary global regulator are Hfq, which is a RNA chaperone mediating interaction of mRNA and sRNA (Example 7) ; ArcZ, a sRNA partner; DNA methyltransferase Dam1; the cAMP synthase CyaA (Example 12). Exemplary global regulators are transcription factors that bind to the regulatory element of DNA of a BGC and help to coordinate the responses of several genes to direct the production of biosynthesis of secondary metabolites. Only non-essential regulators can be addressed with the methodology disclosed herein, as individual clones need to be grown in production cultures to test and verify the effect on natural product production. On the other side, most regulators involved in natural product biosynthesis are non-essential even if they are quite global since the natural products are often not essential. Here might be a slight GAR-P04397WO09 Application (final)2.docx "Bacterial indicator strain" refers to a strain wherein a first BGC of interest is replaced by a first fluorescent reporter and the second BGC of interest is replaced by a second fluorescent reporter. "Bacterial indicator strain" is used interchangeably with "bacterial reporter strain". Thus, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite. The screening of fluorescent reporter strains is preferably performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging. Table 11 reports some fluorescent proteins that can be inserted in a BGC according to the disclosed method. Therefore, the present invention also relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: GAR-P04397WO09 Application (final)2.docx a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging. An embodiment of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, GAR-P04397WO09 Application (final)2.docx g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite. A particular embodiment of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, GAR-P04397WO09 Application (final)2.docx wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging. Random mutagenesis can be performed by a method selected from chemical random mutagenesis, UV mediated random mutagenesis, transposon mutagenesis, or error prone PCR. Transposon mutagenesis allows isolating mutants easily with antibiotic resistance caused by transposon insertion successfully. Accordingly, a particular embodiment of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis. GAR-P04397WO09 Application (final)2.docx A still more particular embodiment of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging, wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis. A further more particular embodiment of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; GAR-P04397WO09 Application (final)2.docx d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis. A still more particular embodiment of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); GAR-P04397WO09 Application (final)2.docx h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis. "Biosynthetic gene cluster" A "biosynthetic gene cluster" (BGC) can be defined as a physically clustered group of two or more genes in a particular genome that together encode a biosynthetic pathway for the production of a specialized metabolite. A "silent BCG" refers to silent or cryptic BGC under standard laboratory growth conditions, so the SM for which are responsible are not produced. Selective activation of a BGC refers to the selective stimulation of the expression of a particular BGC in order to obtain production of the SM for which is responsible at high level. Examples of BGC that can be modulated with the present invention: - encoding enzymes responsible for production of secondary metabolytes, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP). - producing secondary metabolites selected from the group comprising an antibiotic, or an anti-cancer drug, or an immune suppressive drug. - producing a secondary metabolite selected from the group comprising Puromycin, Madumycin II, Xenoamicin, Rupshomycin, safracin. Non-ribosomal peptides (NRP) are not directly encoded in the genome like typical proteins or peptides but are produced by metabolic pathways encoded by BGCs. NRPs are a large family of structurally diverse and pharmacologically GAR-P04397WO09 Application (final)2.docx useful natural products with broad biological activities. Prominent examples are the antibiotic daptomycin or the immunosuppressant cyclosporine A2. They are assembled by multifunctional enzyme complexes called non-ribosomal peptide synthetases (NRPSs) that are organized in a modular fashion. Each module activates and modifies a specific amino acid (aa) that is then subsequently elongated with an aa activated and modified by the next module thereby generating peptides with their length depending on the number of modules used Therefore, a particular embodiment of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP). An alternative embodiment of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: GAR-P04397WO09 Application (final)2.docx a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP). A preferred alternative embodiment of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; GAR-P04397WO09 Application (final)2.docx d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP). A further preferred alternative embodiment of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); GAR-P04397WO09 Application (final)2.docx h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP). A further more preferred alternative embodiment of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; GAR-P04397WO09 Application (final)2.docx wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; wherein said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP). An aspect of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging, wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; GAR-P04397WO09 Application (final)2.docx wherein said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP). A further aspect of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; wherein said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP). GAR-P04397WO09 Application (final)2.docx Another aspect of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; wherein said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP). Secondary metabolites (natural products) Secondary metabolites (SM) are natural products (NP) synthesized mainly by bacteria, fungi and plants. They are molecules of low molecular weight with GAR-P04397WO09 Application (final)2.docx diverse chemical structures and biological activities. Exemplary SMs are pigments, antibiotics, anti-cancer or immune suppressive drugs with applications in medicine, biotechnology and agriculture. Secondary metabolites play important roles in cellular growth and signaling, nutrient acquisition, intra- and interspecies communication, and virulence. A subset of natural products is produced by nonribosomal peptide synthetases (NRPSs). Exemplary SMs are: Safracin compounds, comprising Safracin B that can be used for the semisynthesis of the two chemoterapeutics Ecteinascidin 743 and (–)- Jorumycin (Figures 10, 11), rupshomycin and derivatives produced from rpm BGC (Figure 12-14), Madumycin II (Figure 8, 9), Xenoamicine (Figure 22), Puromycin, Stilbenes (Figure 2, 4), GameXPeptides (gxpS, Figure 7A, Table 10), glidobactin (glbA, Figure 7A), Xenocoumacins (xcnA, Figure 7B, Table 10), Rhabdopeptides (rxpA, Figure 7B), Indigoidine, (indC, Figure 6, Table 10). Genetic loci involved in the biosynthesis of indigoidine have been found in E. chrysanthemi (indA∼indC), V. indigofera (igiA∼igiE) (GenBank™ accession number AF088856), and Photorhabdus luminescens (plu2182, plu2186, and plu2187). indC, igiD, and plu2186 genes in these loci seem to encode NRPS. The glidobactin-like natural products (GLNPs) glidobactin A and cepafungin I have been reported to be potent proteasome inhibitors and are regarded as promising candidates for anticancer drug development. Their biosynthetic gene cluster (BGC) plu1881–1877 is present in entomopathogenic Photorhabdus laumondii but silent under standard laboratory conditions. The plu1881 has the same function as the homologue glbB, i.e. catalysis of the 4-hydroxylation reaction of L-lysine. The biosynthesis of xenortides A-D consists of two NRPS coded by genes XndA and XndB. The XndA consists of a condensation, adenylation, methylation, and thiolation domain, and has been implicated for the loading of N-methylleucine (xenortides A-B) or N-methylvaline (xenortides C-D). The XndB consists of a condensation, adenylation, methylation, thiolation, and terminal condensation domains. XndB has been implicated in elongation with N-methylphenylalanine, as well as the final condensation of the enzyme-bound peptide with either decarboxylated phenylalanine (phenylethylamine in xenortides A and C) or decarboxylated tryptophan (tryptamine in xenortides B and D), ending the biosynthesis. GAR-P04397WO09 Application (final)2.docx In Xenorhabdus and Photorhabdus (XP), GxpS, an NRPS with five modules, is responsible for the biosynthesis of GameXPeptides (Table 10), which are a class of cyclic pentapeptides composed of valine, leucine, and phenylalanine. RXP are rhabdopeptide/xenortide-like peptides (Table 10). Other natural products produced by XP: silathride, xenoautoxin, phenylethylamide, tryptamide, rhabdopeptide, and PAX. Thus, a preferred aspect of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives. GAR-P04397WO09 Application (final)2.docx A more preferred aspect of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging. A still more preferred aspect of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; GAR-P04397WO09 Application (final)2.docx e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives. A further preferred aspect of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; GAR-P04397WO09 Application (final)2.docx i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging. A further more preferred aspect of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising GAR-P04397WO09 Application (final)2.docx Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis. A further still more preferred aspect of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging, wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis. GAR-P04397WO09 Application (final)2.docx The present invention also relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis. The present invention further relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; GAR-P04397WO09 Application (final)2.docx b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis. The present invention alternatively relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; GAR-P04397WO09 Application (final)2.docx c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP). The present invention preferably relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, GAR-P04397WO09 Application (final)2.docx f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP); wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging. An embodiment of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); GAR-P04397WO09 Application (final)2.docx h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP). A particular embodiment of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; GAR-P04397WO09 Application (final)2.docx i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP); wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging. A more particular embodiment of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; GAR-P04397WO09 Application (final)2.docx wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP); wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis. A still more particular embodiment of the the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, GAR-P04397WO09 Application (final)2.docx wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP); wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis. A further more particular embodiment of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; GAR-P04397WO09 Application (final)2.docx wherein said GR gene regulates production of a target secondary metabolite; wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP); wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis. A further still more particular embodiment of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; GAR-P04397WO09 Application (final)2.docx wherein said GR gene regulates production of a target secondary metabolite, wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP); wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis. Contemplated Bacteria: Preferred bacteria for the present invention are Gram negative bacteria (Pseudomonas, Xenorhabdus, Photorhabdus, Serratia, Vibrio etc.) and other strains that produce natural products, such as myxobacteria, cyanobacteria, Pseudomonades, Bacillus, Paenibacillus or Streptomyces. Therefore, an aspect of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); GAR-P04397WO09 Application (final)2.docx h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces. A further aspect of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, and Paenibacillus. GAR-P04397WO09 Application (final)2.docx A further aspect of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein the bacterium is not Streptomyces. A further aspect of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, GAR-P04397WO09 Application (final)2.docx f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces. Preferably, the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, and Paenibacillus. A particular aspect of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; GAR-P04397WO09 Application (final)2.docx i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces. Preferably, the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, and Paenibacillus. A preferable aspect of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, GAR-P04397WO09 Application (final)2.docx wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces. Preferably, the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, and Paenibacillus. An alternative aspect of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; GAR-P04397WO09 Application (final)2.docx wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces. Preferably, the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, and Paenibacillus. A preferred aspect of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging, wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces. GAR-P04397WO09 Application (final)2.docx Preferably, the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, and Paenibacillus. A further preferred aspect of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces. Preferably, the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, and Paenibacillus. GAR-P04397WO09 Application (final)2.docx A more preferred aspect the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces. Preferably, the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, and Paenibacillus. GAR-P04397WO09 Application (final)2.docx A still more preferred aspect the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP); and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces. Preferably, the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, and Paenibacillus. A particular aspect of present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; GAR-P04397WO09 Application (final)2.docx b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP); and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces. Preferably, the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, and Paenibacillus. A more particular aspect of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; GAR-P04397WO09 Application (final)2.docx b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP); and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces. Preferably, the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, and Paenibacillus. A still more particular aspect of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; GAR-P04397WO09 Application (final)2.docx b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP). A further more particular aspect of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; GAR-P04397WO09 Application (final)2.docx d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; wherein said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP); and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces. Preferably, the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, and Paenibacillus. An alternative embodiment of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; GAR-P04397WO09 Application (final)2.docx d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging, wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; wherein said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP); and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces. Preferably, the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, and Paenibacillus. A preferred embodiment of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; GAR-P04397WO09 Application (final)2.docx c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; wherein said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP); and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces. Preferably, the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, and Paenibacillus. A more preferred embodiment of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; GAR-P04397WO09 Application (final)2.docx b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; wherein said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP); and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces. Preferably, the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, and Paenibacillus. GAR-P04397WO09 Application (final)2.docx A still more preferred embodiment of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives, and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces. Preferably, the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, and Paenibacillus. A further more preferred embodiment of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; GAR-P04397WO09 Application (final)2.docx b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging, and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces. Preferably, the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, and Paenibacillus. In particular, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; GAR-P04397WO09 Application (final)2.docx d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives, and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces. Preferably, the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, and Paenibacillus. More in particular, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; GAR-P04397WO09 Application (final)2.docx e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces. Preferably, the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, and Paenibacillus. Also more in particular, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; GAR-P04397WO09 Application (final)2.docx e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces. Preferably, the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, and Paenibacillus. Still more in particular, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; GAR-P04397WO09 Application (final)2.docx e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging, wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces. Preferably, the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, and Paenibacillus. A particular embodiment of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; GAR-P04397WO09 Application (final)2.docx d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces. Preferably, the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, and Paenibacillus. A more particular embodiment of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; GAR-P04397WO09 Application (final)2.docx c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces. Preferably, the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, and Paenibacillus. A further more particular embodiment of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; GAR-P04397WO09 Application (final)2.docx b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP); and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces. Preferably, the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, and Paenibacillus. A further still more particular embodiment of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: GAR-P04397WO09 Application (final)2.docx a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP); wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces. Preferably, the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, and Paenibacillus. GAR-P04397WO09 Application (final)2.docx Preferably, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP); and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces. GAR-P04397WO09 Application (final)2.docx Preferably, the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, and Paenibacillus. More preferably, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP); GAR-P04397WO09 Application (final)2.docx wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces. Preferably, the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, and Paenibacillus. Further preferably, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group GAR-P04397WO09 Application (final)2.docx comprising non-ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP); wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces. Preferably, the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, and Paenibacillus. Further more preferably, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising GAR-P04397WO09 Application (final)2.docx Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP); wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces. Preferably, the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, and Paenibacillus. The present invention also relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; GAR-P04397WO09 Application (final)2.docx i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP); wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces. Preferably, the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, and Paenibacillus. The present invention particularly relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, GAR-P04397WO09 Application (final)2.docx g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP); wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis, and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces. Preferably, the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, and Paenibacillus. CRISPR/Cas based gene editing CRISPR-Cas systems are native to bacteria and Archaea and provide adaptive immunity against viruses and plasmids. The CRISPR-Cas endonuclease system is utilized in genomic engineering as follows: the gRNA complex (either a crRNA:tracrRNA complex or an sgRNA) binds to Cas9, inducing a conformational change that activates Cas9 and opens the DNA binding cleft, the protospacer domain of the crRNA (or sgRNA) aligns with the complementary target DNA and GAR-P04397WO09 Application (final)2.docx Cas9 binds the PAM sequence, initiating unwinding of the target DNA followed by annealing of the protospacer domain to the target, after which cleavage of the target DNA occurs. The Cas9 contains two domains, homologous to endonucleases HNH and RuvC respectively, wherein the HNH domain cleaves the DNA strand complementary to the crRNA and the RuvC-like domain cleaves the non-complementary strand. This results in a double-stranded break in the genomic DNA. When repaired by non-homologous end joining (NHEJ) the break is typically repaired in an imprecise fashion, resulting in the DNA sequence being shifted by 1 or more bases, leading to disruption of the natural DNA sequence and, in many cases, leading to a frameshift mutation if the event occurs in a coding exon of a protein-encoding gene. The break may also be repaired by homology directed recombination (HDR), which permits insertion of new genetic material based upon exogenous DNA introduced into the cell with the Cas9/gRNA complex, which is introduced into the cut site created by Cas9 cleavage A second class 2 CRISPR system, assigned to type V, has been identified. This type V CRISPR-associated system contains Cpf1, which is a ˜1300 amino acid protein—slightly smaller than Cas9 from S. pyogenes. The PAM recognition sequence of Cpf1 is TTTN, in contrast to the NGG PAM recognition domain of S. pyogenes Cas9. Having the ability to target AT-rich areas of the genome will be greatly beneficial to manipulate and study gene targets in regions that are lacking GG dinucleotide motifs. The Cpf1 system is also remarkably simple in that it does not utilize a separate tracrRNA, and only requires a single short crRNA of 40-45 base length that both specifies target DNA sequence and directs binding of the RNA to the Cpf1 nuclease. In contrast to Cas9 which produces blunt-ended cleavage products, Cpf1 facilitates double stranded breaks with 4-5 nucleotide overhangs. The advantage of this is that it may ensure proper orientation as well as providing microhomology during non-homologous end joining (NHEJ). This could also be advantageous in non-dividing cell types that tend to be resistant to homology-directed repair (HDR). Furthermore, when Cpf1 cleaves, it does so further away from PAM than Cas9, which is also further away from the target site. As a result, the protospacer, and especially the seed sequence of the protospacer, are less likely to be edited, thereby leaving open the potential for a second round of cleavage if the desired repair event doesn't happen the first time. The Cpf1 protein forms a complex with a single stranded RNA oligonucleotide to mediate targeted DNA cleavage. The single strand guide RNA oligonucleotide consists of a constant region of 20 nt and a target region of 21-24 nt for an overall length of 41-44 nt. GAR-P04397WO09 Application (final)2.docx A further suitable Cas for the present invention is Cas13. The term "crRNA framework" (crRNA FW) refers to a nucleotide sequence comprising a constitutive or inducible promoter, a crRNA leader, direct repeat, a spacer dummy (comprising a BsaI or BsmbI or any other type II restriction sites for insertion of target spacers A and B), direct repeat, a terminator. Suitable crRNA frameworks for the present invention are shown in Figure 19. The term "crRNA array" refers to a group of nucleotide sequences comprising: - a crRNA framework; - "target" specific target spacers A and/or B inserted inside said crRNA framework; - optionally further elements such as promoter system as defined herein, translational enhancer, fluorescent reporter gene. Thus, a crRNA array is target specific. The target specific crRNA array is formed in the plasmid for gene editing from the elements of the homology arms left and right. The "target" can be for example a gene of a BGC for BGC activation, or a gene of a BGC for silencing or replacement with a FR gene, or a GR for GR deletion. The term "crRNA system" refers to a group of dsDNA fragments (dsDNA nucleotide sequences) comprising: at least one crRNA framework, at least one target spacer A or B, target specific homology region left, target specific homology region right, and optionally a fluorescent reporter gene, or a promoter system or enhancer sequence positioned between said homology region left and said homology region right. A "crRNA leader" sequence can be an AT-rich sequence, but can also be part of the UTR of the promoter, so it is not necessary as an independent component. A "direct repeat" refers to a 36 bp long direct repeat that is an essential part of the crRNA framework and must be encoded upstream of any target specific spacer to be recognized by the Cas protein, such as Cpf1. A repeat after the spacer is not necessary if the spacer has already been shortened to the mature length of 23 bp. GAR-P04397WO09 Application (final)2.docx The term "target spacer" refers to a nucleic acid sequence having the function of "target specific crRNA". A "target spacer" is selected from the genome of the target organism and is located distally after a PAM sequence (in the best-case TTTV). Best editing results can be achieved selecting one spacer for each leading and lagging strand, i.e. target spacer A and target spacer B. It should be avoided to have three or more “T” in the sequence. A GC content of 50% should be aimed at. moreover, a "target spacer" has a nucleic acid sequence with a length between 23 and 31 bp depending on whether there is a direct repeat after the target spacer. A "spacer dummy" refers to a polynucleotide sequence which should not have homology to the target host; and must be accessible for any kind of cloning (Gibson, Golden Gate, Gateway, Restriction cloning). A "spacer dummy" can comprise a reporter gene (e.g. mCherry) or a toxin (e.g. ccdB) to allow identification of the cloning success; A "terminator" or "transcriptional terminator" refers to a target host adapted terminator or standard terminator from the iGEM library (http://parts.igem.org/Terminators/Catalog). The term "homology arm left" (HA-L) refers to a synthetic dsDNA fragment comprising the following elements in this order: spacer with restriction site (e.g. BsaI site), target spacer A or B (TS-A or TS-B), direct repeat (DR), optionally a terminator, homology region left (HR-L), spacer with restriction site (e.g. BsaI site). The target spacer A or B and DR form the "target specific crRNA array" in the assembled single plasmid, e.g. pAR20 in the Examples of this invention. The term "homology arm right" (HA-R) refers to a synthetic dsDNA fragment comprising the following elements in this order: spacer with restriction site (e.g. BsaI site), homology region right (HR-R), a constitutive promoter (e.g. J23119), direct repeat (DR), target spacer A or B (TS-A or TS-B), spacer with restriction site (e.g. BsaI site). The constitutive promoter, crRNA leader, DR, and target spacer form the "target specific crRNA array" in the assembled single plasmid, e.g. pAR20 in the Examples of this invention. GAR-P04397WO09 Application (final)2.docx The term "homology region" left or right refers to a nucleic acid sequence which is contained in the single plasmid for CRISPR/Cas gene editing and is complementary to the target BGC or global regulatory gene. It is used for repair after CRISPR induced double strand break. A nucleic acid sequence for "homology region" left or right depends on the recombination genes and the used strains. A nucleic acid sequence for "homology region" left or right can comprise at least 50, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000 bp (basepair). A nucleic acid sequence for "homology region" left or right can comprise at most 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1200, 1400, 1600, 1700, 1800, 1900, 2000 bp. A nucleic acid sequence for "homology region" left or right preferably comprises between 100 and 500 bp, 100 and 600 bp, 100 and 700 bp, 100 and 800 bp, 100 and 900 bp, 100 and 1000 bp, 100 and 1100 bp, 100 and 1200 bp, 100 and 1300 bp, 100 and 1400 bp, 100 and 1500 bp, 100 and 1600 bp, 100 and 1700 bp, 100 and 1800 bp, 100 and 1900 bp, 100 and 2000 bp, 50 and 500 bp, 50 and 600 bp, 50 and 700 bp, 50 and 800 bp, 50 and 900 bp, 50 and 1000 bp, 50 and 1100 bp, 50 and 1200 bp, 50 and 1300 bp, 50 and 1400 bp, 50 and 1500 bp, 50 and 1600 bp, 50 and 1700 bp, 50 and 1800 bp, 50 and 1900 bp, 50 and 2000 bp, The present invention alternatively relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; GAR-P04397WO09 Application (final)2.docx wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. More in particular, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. GAR-P04397WO09 Application (final)2.docx In other embodiments, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. In particular embodiments, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; GAR-P04397WO09 Application (final)2.docx c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. In particular embodiments, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, GAR-P04397WO09 Application (final)2.docx f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. In preferred embodiments, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; GAR-P04397WO09 Application (final)2.docx wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging, wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis, wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. In more preferred embodiments, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; GAR-P04397WO09 Application (final)2.docx wherein said GR gene regulates production of a target secondary metabolite; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. In alternative embodiments, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; GAR-P04397WO09 Application (final)2.docx wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. In further embodiments, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP); wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and GAR-P04397WO09 Application (final)2.docx second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. More in particular, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP); wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. GAR-P04397WO09 Application (final)2.docx The present invention further relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP); wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. The present invention also relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; GAR-P04397WO09 Application (final)2.docx b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP); wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. The present invention is also directed to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; GAR-P04397WO09 Application (final)2.docx b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; wherein said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP); wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. More in particular, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; GAR-P04397WO09 Application (final)2.docx c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging, wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; wherein said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP); wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. The present invention preferably relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; GAR-P04397WO09 Application (final)2.docx c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; wherein said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP); wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. The present invention more preferably relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; GAR-P04397WO09 Application (final)2.docx c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; wherein said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP); wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. The present invention still more preferably relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; GAR-P04397WO09 Application (final)2.docx b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. The present invention further more preferably relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; GAR-P04397WO09 Application (final)2.docx d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. The present invention also preferentially relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); GAR-P04397WO09 Application (final)2.docx h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. The present invention more preferentially relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; GAR-P04397WO09 Application (final)2.docx i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. The present invention more preferentially relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; GAR-P04397WO09 Application (final)2.docx wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. The present invention still more preferentially relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, GAR-P04397WO09 Application (final)2.docx wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging, wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. Thus, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; GAR-P04397WO09 Application (final)2.docx wherein said GR gene regulates production of a target secondary metabolite; wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. In a particular aspect, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, GAR-P04397WO09 Application (final)2.docx wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. Thus, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; GAR-P04397WO09 Application (final)2.docx wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP); wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. More in particular, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising GAR-P04397WO09 Application (final)2.docx Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP); wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. Thus, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; GAR-P04397WO09 Application (final)2.docx wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP); wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. More in particular, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, GAR-P04397WO09 Application (final)2.docx wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP); wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. In an aspect, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; GAR-P04397WO09 Application (final)2.docx wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP); wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. More in particular, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; GAR-P04397WO09 Application (final)2.docx wherein said GR gene regulates production of a target secondary metabolite, wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP); wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. Moreover, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; GAR-P04397WO09 Application (final)2.docx i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP); wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. More in particular, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); GAR-P04397WO09 Application (final)2.docx h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP); wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. Thus, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; GAR-P04397WO09 Application (final)2.docx e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. More in particular, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); GAR-P04397WO09 Application (final)2.docx h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. Thus, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; GAR-P04397WO09 Application (final)2.docx wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. More in particular, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, GAR-P04397WO09 Application (final)2.docx wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. Thus, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; GAR-P04397WO09 Application (final)2.docx wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. More in particular, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging, wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; GAR-P04397WO09 Application (final)2.docx wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. In a further more particular embodiment, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; GAR-P04397WO09 Application (final)2.docx and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. In a still more particular embodiment, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; GAR-P04397WO09 Application (final)2.docx and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. In a more particular embodiment, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP); and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces; GAR-P04397WO09 Application (final)2.docx wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. In a more particular embodiment,the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP); and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces; GAR-P04397WO09 Application (final)2.docx wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. In a particular embodiment, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP); and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces; GAR-P04397WO09 Application (final)2.docx wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. In a particular aspect, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP); wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and GAR-P04397WO09 Application (final)2.docx second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. Morevoer, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; wherein said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP); and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and GAR-P04397WO09 Application (final)2.docx second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. In other particular embodiments, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging, wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; wherein said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP); and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces; GAR-P04397WO09 Application (final)2.docx wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. In other alternative embodiments, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; wherein said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP); GAR-P04397WO09 Application (final)2.docx and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. In other particular embodiments, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; GAR-P04397WO09 Application (final)2.docx wherein said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP); and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. In other preferred embodiments, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising GAR-P04397WO09 Application (final)2.docx Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives, and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. In other embodiments, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging, and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces; GAR-P04397WO09 Application (final)2.docx wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. A further aspect of present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives, and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces; GAR-P04397WO09 Application (final)2.docx wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. A still more particular aspect of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; GAR-P04397WO09 Application (final)2.docx and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. A more particular aspect of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; GAR-P04397WO09 Application (final)2.docx and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. A particular aspect of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging, GAR-P04397WO09 Application (final)2.docx wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. A particular embodiment of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising GAR-P04397WO09 Application (final)2.docx Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. An alternative embodiment of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, GAR-P04397WO09 Application (final)2.docx wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. A preferred embodiment of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; GAR-P04397WO09 Application (final)2.docx wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP); and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. A particular embodiment of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; GAR-P04397WO09 Application (final)2.docx wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP); wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. An embodiment of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); GAR-P04397WO09 Application (final)2.docx h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP); and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. More in particular, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, GAR-P04397WO09 Application (final)2.docx f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP); wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. Thus, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; GAR-P04397WO09 Application (final)2.docx c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP); wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. More in particular, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: GAR-P04397WO09 Application (final)2.docx a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP); wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces; GAR-P04397WO09 Application (final)2.docx wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. A particular embodiment of the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite; wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP); GAR-P04397WO09 Application (final)2.docx wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis; and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. More in particular, the present invention relates to a method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in steps a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite, wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising GAR-P04397WO09 Application (final)2.docx Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non-ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP); wherein the step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging; wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV-mediated random mutagenesis, or error-prone PCR or transposon mutagenesis, and wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, Paenibacillus and Streptomyces; wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA array, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. "Plasmids" A "helper plasmid" is a plasmid for a bacterium that provides functions required for efficient recombination. For CRISPR/Cas system, an helper plasmid contains the gene encoding the endonuclease Cas12a (Cpf1) under an inducible promoter, and a lambda red (gam, exo, bet) recombination system under an inducible promoter. A "donor plasmid" is a plasmid carrying a crRNA sequence for a specific target gene under a constitutive promoter or a strong constitutive promoter or an inducible promoter, as well as homology regions left and right to the target gene serving as repair templates after double strand break. "Promoter" refers to genetic elements controlling the binding of RNA polymerase and transcription factors. Since the promoter region drives transcription of a target gene, it therefore determines the timing of gene expression and largely defines the amount of recombinant protein that will be produced. A promoter can be specific for a species or genus, but often a promoter from a bacterium can function well in a distantly related bacterium. For example, a GAR-P04397WO09 Application (final)2.docx promoter from Bacillus subtilis or a phage that normally grows on B. subtilis can function well in E. coli. "Constitutive promoter" refers to promoters that are always active. Suitable examples are rpsL (30S ribosomal subunit protein S12(V00355.1)), Amp (bla, BBa_I14018) promoter Suitable promoters to carry out the methods described herein are disclosed in Shimada T. et al., The Whole Set of Constitutive Promoters Recognized by RNA Polymerase RpoD Holoenzyme of Escherichia coli. PLoS ONE 2014, 9(3): e90447. Further constitutive artificial promoter can be found in Anderson library: ‘Promoters/Catalog/Anderson’, http://parts.igem.org/Promoters/Catalog/Anderson. Promoters from primary metabolism or from ribosomal proteins can be used herein, as for example: glyceraldehyde-3-phosphate dehydrogenase promoter (GenBank: CP097883.1) or ribosomal protein S12 promoter (GenBank: CP097884.1). "Strong constitutive promoter" are for examples the strong constitutive from Bacillus subtilis phage SP01, and coliphage lambda PR, and PJ23119 from the Anderson library. "Inducible promoters" refer to promoters that are only active under specific circumstances and which can be switched from an OFF to an ON state, or from an ON to an OFF state. Inducible promoters suitable for expression of cpf1 and recombinases in the present invention are AraC - P^BAD (Meyer AJ 2019, Nature Chemical Biology 15, 196 - 204), LacI – P^tac (^{Meyer AJ 2019)}, the xylose-inducible expression system: xutR - Pxut, Genbank MT344942, and MN857504, and the L-rhamnose-inducible promoter from Burkholderia, P^rhaBAD, controlled by AraC/XylS-family transcriptional regulators rhaS and rhaR (Hogan AM et al., 2021. Appl Environ Microbiol 87:e00647-21). Inducible promoter systems have been described in the prior art (e.g. in Meyer AJ 2019), and comprise the following elements: a 3'-Terminator, a repressor / regulator gene (Table 6), a RBS specific for the regulator (Table 6), a strong constitutive promotor for expression of the regulator (Table 6), a terminator to separate regulator regulation from target gene regulation: (ex.: L3S2P21), a Insulator element (examples listed below), a strong RBS for target gene, such as BBa_B0064. GAR-P04397WO09 Application (final)2.docx The vanillic Acid promoter system (SEQ ID NO 131, 132) used in the examples of the present invention comprises the following elements: PvanCC modified (Promoter), BBa_B0064 (RBS), RiboJ (Insulator), RiboJ51 (Insulator). The expression of a gene cluster can be increased by additionally introducing "enhancer sequences" such as a T7g10 transcriptional enhancer, or a "translation enhancement by a Dictyostelium gene sequence", TED sequence. The transcriptional enhancer T7g10 (also abbreviated as g10T7 UTR), (SEQ ID NO:135, comprising BBa_K1758100, sequence available online) comprises a 5' untranslated region (5'-UTR) and a strong ribosomal binding site from bacteriophage T7 gene 10 (g10-L). The TED sequence derived by a Dictyostelium has to be placed upstream of the Shine–Dalgarno sequence located between the promoter and the initiation codon of a target gene in order to achieve an enhancement in gene expression. Suitable TED sequences are mlcR sequences, such as mlcR10, mlcR20, mlcR25, mlcR30, mlcR40, mlcR45, mlcR60, and mlcR74, previously described by Kondo and Yumura 2019, Applied Microbiology and Biotechnology 103:3501–3510. Further enhancement sequences and structures has been described in Xiao et al., ACS Synth. Biol., 9, 1051−1058 The wording "refactoring" refers to the manipulation of a BGC cluster comprising: replacing natural promoters with constitutive or readily inducible promoters andheterologous expression in strains optimized for heterologous expression. BGC refactoring has thus the potential to provide access to the chemical diversity encoded by silent BGCs. Table 1: Elements of the suitable promoter systems for promoter exchange Inducer Regula- Output Promoter _{RBS Notes} ^Ref. tor (R) Promoter for R DAPG, PhlF^AM P_PhlF P_J23119 phl2 PhlF is a Meyer 2,4- TetR family AJ (diacetylpho repressor 2019 phloroglucin from ol) P.fluorescens Cumic acid CymR^AM PCymRC PJ23119 cym1 CymR is a Meyer TetR family AJ repressor 2019 from P.putida GAR-P04397WO09 Application (final)2.docx OC6 luxR _{PluxB PJ23119} lux1 LuxR is an Meyer activator from AJ Vibrio fischeri 2019 Van VanR^AM PVanCC PJ23119 van2 VanR is a Meyer (vanillic GntR family AJ acid) repressor 2019 from Caulobacter crescentus IPTG LacI^AM PTac PLaclR lac1 LaI is a Meyer repressor AJ from E. coli. 2019 a^{Tc tetR P} _{tet PLaclR} ^tet1 _{TetR is a} Meyer repressor AJ from E. coli 2019 Ara AraC^AM, PBAD PLaclR ara1, AraC is Meyer (L- araE e1 activator AJ arabinose) /repressor 2019 from E. coli. Cho BetI^AM P_BetI P_J23100 bet2 BetI is a TetR Meyer (choline family AJ chloride) repressor 2019 from E. coli. Nar TtgR^AM PTtg PJ23100 ttg2 TtgR is a Meyer (naringenin) TetR family AJ repressor 2019 from P. putida DHBA PcaU^AM P3B5B PJ23100 pca2 PcaU is a Meyer (3,4- IcIR family AJ dihydroxybe repressor 2019 nzoic acid) from Acineto- bacter sp. Sal NahR^AM PSalTTC PJ23100 nah2 NahR is a Meyer (sodium LysR family AJ salicylate) activator from 2019 P. putida OHC14 CinR^AM PCin PJ23100 cln1 CinR is a Meyer (3- LuxR family AJ Hydroxytetr activator from 2019 adecanoyl- Rhizobium homoserine leguminosaru lactone) m Suitable Insulators are RiboJ, RiboJ10, RiboJ51, RiboJ53, BydvJ, ElvJ. (Meyer AJ, 2019), LtsvJ, SccJ, SarJ, PlmJ, and VtmoJ (Lou et al., Nat Biotechnol 2012, 30 (11), 1137-42). GAR-P04397WO09 Application (final)2.docx Suitable Terminators are B0053, ECK120017009, ECK120033736, ECK120033737, IOT, L3S2P21, L3S3P21, L3S2P56, L3S3P41, L3S1P52, L3S2P41. (Meyer AJ, 2019). The system of the Xylose inducible promotor PxylA comprises a modified 5-UTR containing g10-L RBS (RBS from gene 10 of the T7 phage 5), a strong ribosomal binding site from bacteriophage T7. This sequence greatly enhances translation of a following gene. The sequence can be found at https://parts.igem.org/Part:BBa_K1758100. Suitable recombinase systems: Recombineering system based on three Rac bacteriophage RecET-like operons: RecETheBDU8, RecEThTJI49 and RecETh1h2eYI23, optionally combined with exonuclease inhibitors Pluγ or Redγ. RecETheBDU8 from Burkholderia sp. BDU8 harbours a four-gene operon predicted to encode: the YqaJ viral recombinase family protein RecEBDU8 (protein ID: KVE53656.1; locus tag: WS71_06320); the recombinase RecTBDU8 (protein ID: KVE53655.1; locus tag: WS71_06315); and two hypothetical proteins hBDU8 (protein ID: KVE53654.1; locus tag: WS71_06310) and eBDU8 (protein ID: KVE53653.1; locus tag: WS71_06305). The operon, RecEThTJI49 from Burkholderia sp. TJI49, is predicted to encode the following three proteins: the hypothetical protein RecETJI49 (protein ID: EGD06616.1; locus tag: B1M_00520),; the phage-related DNA recombination protein RecTTJI49 (protein ID: EGD06615.1; locus tag: B1M_00515); and the hypothetical protein hTJI49 (protein ID: EGD06614.1; locus tag: B1M_00510). The third operon, RecETh1h2eYI23 from Burkholderia cordobensis YI23, contains genes encoding the putative 5′-3′ specific dsDNA exonuclease RecEYI23 (protein ID: AET91062.1; locus tag: BYI23_B004550); the putative recombinase protein RecTYI23 (protein ID: AET91060.1; locus tag: BYI23_B004530),; three hypothetical proteins h1YI23 (protein ID: AET91061.1; locus tag: BYI23_B004540), h2YI23 (protein ID: AET91063.1; locus tag: BYI23_B004560) and eYI23 (protein ID: AET91059.1; locus tag: BYI23_B004520). Ruijuan Li et al., Microb. Biotechnol. (2021) 14( 4), 1809– 1826. Pseudomonas endogenous phage recombinant systems BAS and RecETpsy, (Yin et al., iScience 14, 1–14, April 26, 2019), E. coli Red and Plu Red recombinant proteins Redγβα and Pluγβα (Yin et al., 2019) GAR-P04397WO09 Application (final)2.docx Photorhabdus luminescens lambda Red-like operon, Plu2934/Plu2935/Plu2936, Jia Yin, et al., Nucleic Acids Research, 43(6), 2015, e36. A number of selectable marker genes are known in the art and several antibiotic resistance markers satisfy these criteria, including those conferring resistance to hygromycin, kanamycin, bleomycin, G418, streptomycin or spectinomycin, ampicillin, tetracycline, neomycin, Zeocin™, and the like. A preferred negative selectable marker gene is SacB. SacB (Bacillus subtilis levansucrase) is a counterselectable marker which is lethal to E. coli cells in the presence of sucrose. SacB encoded levansucrase converts sucrose to levans, which is harmful to the bacteria, and allows plasmid selection on sucrose. The sacB gene including its native promoter can be amplified with AR432/433 from pEP17-KM. A further preferred negative selectable marker gene is mutated PheS, which encodes α-subunit of phenylalanyl tRNA synthase. Counterselection is with 0.1% p-chlorophenylalanine), GenBank EU329004.1. Single plasmid for gene editing A "single-plasmid" refers to a plasmid comprising elements of helper plasmid, donor plasmid, optionally repair template, and positive and negative selectable markers. In detail, the present invention relates to the following types of plasmids for CRISPR/Cas based gene editing: A single plasmid for replacement of a BGC with a fluorescent reporter (Figure 1B) comprises the following sequences: - first crRNA array comprising a crRNA FW (J23119, DR, DR, Term) with a BGC specific TS-A inserted in the spacer dummy of the crRNA FW. - BGC specific HR-L complementary to a genome sequence positioned upstream said BGC gene; - Fluorescent Reporter gene (for example a gene encoding for a protein of Table 11) - BGC specific HR-R complementary to a genome sequence positioned downstream said BGC gene; - second crRNA array comprising a crRNA FW (J23119, DR, DR, Term) with a BGC specific TS-B inserted in the spacer dummy of the crRNA FW. GAR-P04397WO09 Application (final)2.docx TS-A and TS-B are selected inside the target gene (GOI= gene of interest) of the BGC, at a variable distance between them. A single plasmid for activation of a BGC by promoter exchange (Figure 1C, 6A-C) comprises the following sequences: - first crRNA array comprising a crRNA FW (J23119, DR, DR, Term) with a BGC specific TS-A inserted in the spacer dummy of the crRNA FW. - BGC specific HR-L complementary to a genome sequence positioned upstream to said BGC gene; - Promoter system, e.g.: repressor with constitutive promoter and Terminator all in reverse direction; an Inducible Promoter; - BGC specific HR-R complementary to a genome sequence positioned inside said BGC gene; - second crRNA array comprising a crRNA FW (J23119, DR, DR, Term) with a BGC specific TS-B inserted in the spacer dummy of the crRNA FW. Both TS-A and TS-B are situated in the genome before the target gene (GOI= gene of interest) of the BGC, at a variable distance between them. A single plasmid for inactivation or deletion of a GR (Example 12; Figure 2 shows the optimization process to obtain such a single plasmid) comprises the following sequences: - first crRNA array comprising a crRNA FW (J23119, DR, DR, Term) with a GR specific TS-A inserted in the spacer dummy of the crRNA FW. - GR specific HR-L complementary to a genome sequence positioned upstream the GR; - GR specific HR-R complementary to a genome sequence positioned downstream the GR; - second crRNA array comprising a crRNA FW (J23119, DR, DR, Term) with a GR specific TS-B inserted in the spacer dummy of the crRNA FW. TA-A and TS-B are selected inside the target gene (GOI= gene of interest) of the GR, at a variable distance between them. A preferred embodiment of the present invention is directed to a recombination single-plasmid to activate or silence a BGC in a bacterium by CRISPR/Cas- mediated homology-directed repair, the plasmid comprising: an origin of transfer sequence (oriT), a cas gene under control of a first inducible promoter, GAR-P04397WO09 Application (final)2.docx genes for a suitable recombinase system under control of a second inducible promoter, at least one positive selectable marker gene, at least one negative selectable marker gene, a crRNA system selected from the group consisting of: I) a crRNA system to activate a BGC comprising: at least one crRNA framework, at least one target spacer specific for a genome sequence positioned upstream to a BGC gene, homology region left complementary to a genome sequence positioned upstream to said BGC gene, homology region right complementary to a genome sequence positioned inside said BGC gene, and a promoter system positioned between said homology region left and said homology region right, and optionally an enhancer sequence; II) a crRNA system to silence a BGC or to delete or inactivate a GR comprising: at least one crRNA framework, at least one target spacer specific for a genome sequence positioned inside a BGC gene or inside said GR, homology region left complementary to a genome sequence positioned upstream said BGC gene or said GR, homology region right complementary to a genome sequence positioned downstream said BGC gene or said GR, and optionally a fluorescent reporter gene positioned between said homology region left and said homology region right. A more preferred embodiment of the present invention is directed to a recombination single-plasmid to activate or silence a BGC in a bacterium by CRISPR/Cas- mediated homology-directed repair, the plasmid comprising: an origin of transfer sequence (oriT), a cas gene under control of a first inducible promoter, genes for a suitable recombinase system under control of a second inducible promoter, at least one positive selectable marker gene, at least one negative selectable marker gene, a crRNA system selected from the group consisting of: I) a crRNA system to activate a BGC comprising: at least one crRNA framework, GAR-P04397WO09 Application (final)2.docx at least one target spacer specific for a genome sequence positioned upstream to a BGC gene, homology region left complementary to a genome sequence positioned upstream to said BGC gene, homology region right complementary to a genome sequence positioned inside said BGC gene, and a promoter system positioned between said homology region left and said homology region right, and optionally an enhancer sequence; II) a crRNA system to silence a BGC or to delete or inactivate a GR comprising: at least one crRNA framework, at least one target spacer specific for a genome sequence positioned inside a BGC gene or inside said GR, homology region left complementary to a genome sequence positioned upstream said BGC gene or said GR, homology region right complementary to a genome sequence positioned downstream said BGC gene or said GR, and optionally a fluorescent reporter gene positioned between said homology region left and said homology region right; and wherein the Cas is selected from the group comprising Cas9, Cas12, and Cas13. Method to elicit production of a secondary metabolite An embodiment of the present invention relates to a method to elicit production of a secondary metabolite from a BGC in a bacterium, wherein the method comprises the following steps: i) deleting a GR gene in said bacterium, and ii) optionally activating a BGC in said bacterium; or wherein the method comprises the following steps: i') essentially activating a BGC in said bacterium, and ii') optionally deleting a GR gene in said bacterium; and the method further comprises: iii) expressing in said bacterium at least one positive selectable marker gene and at least one negative selectable marker gene; wherein deleting a GR gene of steps i) or ii') comprises introducing in said bacterium at least one GR specific siRNA, or a group of sequences comprising a Cas gene, at least one GR specific crRNA array, a pair of GR specific homology regions left and right; and/or wherein activating a BGC of steps ii) or i') comprises introducing in said bacterium a group of sequences comprising a Cas gene, at least one BGC specific GAR-P04397WO09 Application (final)2.docx crRNA array, a pair of BGC specific homology regions left and right, a promoter system, and optionally an enhancer sequence. Reworded, the method to elicit production of a secondary metabolite by a bacterium, wherein the method comprises the following steps: i) deleting a global regulator (GR) gene in said bacterium, and ii) optionally activating a biosynthetic gene cluster (BGC) involved in production of said secondary metabolite in said bacterium; or wherein the method comprises the following steps: i') essentially activating a biosynthetic gene cluster (BGC) involved in production of said secondary metabolite in said bacterium, and ii') optionally deleting a GR gene in said bacterium; and the method further comprises: iii) expressing in said bacterium at least one positive selectable marker gene and at least one negative selectable marker gene; wherein deleting a GR gene of steps i) or ii') comprises introducing in said bacterium at least one GR specific siRNA, or a group of sequences comprising a Cas gene, at least one GR specific crRNA array, a pair of GR specific homology regions left and right; and/or wherein activating a BGC of steps ii) or i') comprises introducing in said bacterium a group of sequences comprising a Cas gene, at least one BGC specific crRNA array, a pair of BGC specific homology regions left and right, a promoter system, and optionally an enhancer sequence. A preferred embodiment of the present invention relates to a method to elicit production of a secondary metabolite from a BGC in a bacterium, wherein the method comprises the following steps: i) deleting a GR gene in said bacterium, and ii) optionally activating a BGC in said bacterium; or wherein the method comprises the following steps: i') essentially activating a BGC in said bacterium, and ii') optionally deleting a GR gene in said bacterium; and the method further comprises: iii) expressing in said bacterium at least one positive selectable marker gene and at least one negative selectable marker gene; wherein deleting a GR gene of steps i) or ii’) comprises introducing in said bacterium a group of sequences comprising a Cas gene, at least one GR specific crRNA array, a pair of GR specific homology regions left and right; and/or GAR-P04397WO09 Application (final)2.docx wherein activating a BGC of steps ii) or i’) comprises introducing in said bacterium a group of sequences comprising a Cas gene, at least one BGC specific crRNA array, a pair of BGC specific homology regions left and right, a promoter system, and optionally an enhancer sequence. A more preferred embodiment of the present invention relates to a method to elicit production of a secondary metabolite from a BGC in a bacterium, wherein the method comprises the following steps: i) deleting a GR gene in said bacterium, and ii) optionally activating a BGC in said bacterium; or wherein the method comprises the following steps: i') essentially activating a BGC in said bacterium, and ii') optionally deleting a GR gene in said bacterium; and the method further comprises: iii) expressing in said bacterium at least one positive selectable marker gene and at least one negative selectable marker gene; wherein deleting a GR gene of steps i) or ii’) comprises introducing in said bacterium at least one GR specific siRNA, or a group of sequences comprising a Cas gene, at least one GR specific crRNA array, a pair of GR specific homology regions left and right; and/or wherein activating a BGC of steps ii) or i’) comprises introducing in said bacterium a group of sequences comprising a Cas gene, at least one BGC specific crRNA array, a pair of BGC specific homology regions left and right, a promoter system, and optionally an enhancer sequence; wherein the Cas is selected from the group comprising Cas9, Cas12 and Cas13. A further more preferred embodiment of the present invention relates to a method to elicit production of a secondary metabolite from a BGC in a bacterium, wherein the method comprises the following steps: i) deleting a GR gene in said bacterium, and ii) optionally activating at least 2 BGCs in said bacterium; or wherein the method comprises the following steps: i') essentially activating at least 2 BGCs in said bacterium, and ii') optionally deleting a GR gene in said bacterium; and the method further comprises: iii) expressing in said bacterium at least one positive selectable marker gene and at least one negative selectable marker gene; GAR-P04397WO09 Application (final)2.docx wherein deleting a GR gene of steps i) or ii’) comprises introducing in said bacterium at least one GR specific siRNA, or a group of sequences comprising a Cas gene, at least one GR specific crRNA array, a pair of GR specific homology regions left and right; and/or wherein activating a BGC of steps ii) or i’) comprises introducing in said bacterium a group of sequences comprising a Cas gene, at least one BGC specific crRNA array, a pair of BGC specific homology regions left and right, a promoter system, and optionally an enhancer sequence. A more preferred alternative embodiment of the present invention relates to a method to elicit production of a secondary metabolite from a BGC in a bacterium, wherein the method comprises the following steps: i) deleting a GR gene in said bacterium, and ii) optionally activating a BGC in said bacterium; or wherein the method comprises the following steps: i') essentially activating a BGC in said bacterium, and ii') optionally deleting a GR gene in said bacterium; and the method further comprises: iii) expressing in said bacterium at least one positive selectable marker gene and at least one negative selectable marker gene; wherein deleting a GR gene of steps i) or ii’) comprises introducing in said bacterium at least one GR specific siRNA, or a group of sequences comprising a Cas gene, at least one GR specific crRNA array, a pair of GR specific homology regions left and right; and/or wherein activating a BGC of steps ii) or i’) comprises introducing in said bacterium a group of sequences comprising a Cas gene, at least one BGC specific crRNA array, a pair of BGC specific homology regions left and right, a promoter system, and optionally an enhancer sequence; wherein said BGC is selected from the group comprising puromycin, madumycin II, xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives. An embodiment of the present invention relates to a method to elicit production of a secondary metabolite from a BGC in a bacterium, wherein the method comprises the following steps: i) deleting a GR gene in said bacterium, and ii) optionally activating at least 2 BGCs in said bacterium; or wherein the method comprises the following steps: i') essentially activating at least 2 BGCs in said bacterium, and GAR-P04397WO09 Application (final)2.docx ii') optionally deleting a GR gene in said bacterium; and the method further comprises: iii) expressing in said bacterium at least one positive selectable marker gene and at least one negative selectable marker gene; wherein deleting a GR gene of steps i) or ii’) comprises introducing in said bacterium at least one GR specific siRNA, or a group of sequences comprising a Cas gene, at least one GR specific crRNA array, a pair of GR specific homology regions left and right; and/or wherein activating a BGC of steps ii) or i’) comprises introducing in said bacterium a group of sequences comprising a Cas gene, at least one BGC specific crRNA array, a pair of BGC specific homology regions left and right, a promoter system, and optionally an enhancer sequence; wherein said BGC is selected from the group comprising puromycin, madumycin II, xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives. A particularly more preferred embodiment of the present invention relates to a method to elicit production of a secondary metabolite from a BGC in a bacterium, wherein the method comprises the following steps: i) deleting a GR gene in said bacterium, and ii) optionally activating a BGC in said bacterium; or wherein the method comprises the following steps: i') essentially activating a BGC in said bacterium, and ii') optionally deleting a GR gene in said bacterium; and the method further comprises: iii) expressing in said bacterium at least one positive selectable marker gene and at least one negative selectable marker gene; wherein deleting a GR gene of steps i) or ii’) comprises introducing in said bacterium at least one GR specific siRNA, or a group of sequences comprising a Cas gene, at least one GR specific crRNA array, a pair of GR specific homology regions left and right; and/or wherein activating a BGC of steps ii) or i’) comprises introducing in said bacterium a group of sequences comprising a Cas gene, at least one BGC specific crRNA array, a pair of BGC specific homology regions left and right, a promoter system, and optionally an enhancer sequence; wherein the step i) - iii) are performed using an automated liquid handling robotics, and wherein said robotics enables high-throughput manipulation of liquid added to or removed from cultures comprising the bacteria. GAR-P04397WO09 Application (final)2.docx A preferable embodiment of the present invention relates to a method to elicit production of a secondary metabolite from a BGC in a bacterium, wherein the method comprises the following steps: i) deleting a GR gene in said bacterium, and ii) optionally activating at least 2 BGCs in said bacterium; or wherein the method comprises the following steps: i') essentially activating at least 2 BGCs in said bacterium, and ii') optionally deleting a GR gene in said bacterium; and the method further comprises: iii) expressing in said bacterium at least one positive selectable marker gene and at least one negative selectable marker gene; wherein deleting a GR gene of steps i) or ii’) comprises introducing in said bacterium at least one GR specific siRNA, or a group of comprising a Cas gene, at least one GR specific crRNA array, a pair of GR specific homology regions left and right; and/or wherein activating a BGC of steps ii) or i’) comprises introducing in said bacterium a group of sequences comprising a Cas gene, at least one BGC specific crRNA array, a pair of BGC specific homology regions left and right, a promoter system, and optionally an enhancer sequence; wherein the step i) - iii) are performed using an automated liquid handling robotics, and wherein said robotics enables high-throughput manipulation of liquid added to or removed from cultures comprising the bacteria. A further more preferable embodiment of the present invention relates to a method to elicit production of a secondary metabolite from a BGC in a bacterium, wherein the method comprises the following steps: i) deleting a GR gene in said bacterium, and ii) optionally activating a BGC in said bacterium; or wherein the method comprises the following steps: i') essentially activating a BGC in said bacterium, and ii') optionally deleting a GR gene in said bacterium; and the method further comprises: iii) expressing in said bacterium at least one positive selectable marker gene and at least one negative selectable marker gene; wherein deleting a GR gene of steps i) or ii’) comprises introducing in said bacterium at least one GR specific siRNA, or a group of sequences comprising a Cas gene, at least one GR specific crRNA array, a pair of GR specific homology regions left and right; and/or GAR-P04397WO09 Application (final)2.docx wherein activating a BGC of steps ii) or i’) comprises introducing in said bacterium a group of sequences comprising a Cas gene, at least one BGC specific crRNA array, a pair of BGC specific homology regions left and right, a promoter system, and optionally an enhancer sequence; wherein said BGC is selected from the group comprising puromycin, madumycin II, xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein the step i) - iii) are performed using an automated liquid handling robotics, and wherein said robotics enables high-throughput manipulation of liquid added to or removed from cultures comprising the bacteria. A more preferred aspect of the present invention relates to a method to elicit production of a secondary metabolite from a BGC in a bacterium, wherein the method comprises the following steps: i) deleting a GR gene in said bacterium, and ii) optionally activating at least 2 BGCs in said bacterium; or wherein the method comprises the following steps: i') essentially activating at least 2 BGCs in said bacterium, and ii') optionally deleting a GR gene in said bacterium; and the method further comprises: iii) expressing in said bacterium at least one positive selectable marker gene and at least one negative selectable marker gene; wherein deleting a GR gene of steps i) or ii’) comprises introducing in said bacterium at least one GR specific siRNA, or a group of sequences comprising a Cas gene, at least one GR specific crRNA array, a pair of GR specific homology regions left and right; and/or wherein activating a BGC of steps ii) or i’) comprises introducing in said bacterium a group of sequences comprising a Cas gene, at least one BGC specific crRNA array, a pair of BGC specific homology regions left and right, a promoter system, and optionally an enhancer sequence; wherein said BGC is selected from the group comprising puromycin, madumycin II, xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives; wherein the step i) - iii) are performed using an automated liquid handling robotics, and wherein said robotics enables high-throughput manipulation of liquid added to or removed from cultures comprising the bacteria. A particularly preferred embodiment of the present invention is a method to elicit production of a secondary metabolite from a BGC in a bacterium, wherein the method comprises the following steps: i) deleting CyaA gene in said bacterium, and GAR-P04397WO09 Application (final)2.docx ii) optionally activating a BGC in said bacterium; or wherein the method comprises the following steps: i') essentially activating a BGC in said bacterium, and ii') optionally deleting a CyaA gene in said bacterium; and the method further comprises: iii) expressing in said bacterium at least one positive selectable marker gene and at least one negative selectable marker gene; wherein deleting a CyaA gene of steps i) or i') comprises introducing in said bacterium at least one CyaA specific siRNA, or a group of sequences comprising a Cas gene, at least one CyaA specific crRNA array, a pair of CyaA specific homology regions left and right; and/or wherein activating a BGC of steps ii) or i’) comprises introducing in said bacterium a group of sequences comprising a Cas gene,at least one BGC specific crRNA array, a pair of BGC specific homology regions left and right; a promoter system sequence, and optionally an enhancer sequence. A particularly more preferred embodiment of the present invention is a method to elicit production of a secondary metabolite from a BGC in a bacterium, wherein the method comprises the following steps: i) deleting CyaA gene in said bacterium, and ii) optionally activating a BGC in said bacterium; or wherein the method comprises the following steps: i') essentially activating a BGC in said bacterium, and ii') optionally deleting a CyaA gene in said bacterium; and the method further comprises: iii) expressing in said bacterium at least one positive selectable marker gene and at least one negative selectable marker gene; wherein deleting a CyaA gene of steps i) or i') comprises introducing in said bacterium at least one CyaA specific siRNA, or a group of sequences comprising a Cas gene, at least one CyaA specific crRNA array, a pair of CyaA specific homology regions left and right; ; and/or wherein activating a BGC of steps ii) or i’) comprises introducing in said bacterium a group of sequences comprising a Cas gene, at least one BGC specific crRNA array, a pair of BGC specific homology regions left and right, a promoter system sequence, and optionally an enhancer sequence , and wherein said BGC is selected from the group comprising puromycin, madumycin II, xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives. GAR-P04397WO09 Application (final)2.docx A further more preferred embodiment of the present invention is a method to elicit production of a secondary metabolite from a BGC in a bacterium, wherein the method comprises the following steps: i) deleting CyaA gene in said bacterium, and ii) optionally activating xenoamicin BGC in said bacterium; or wherein the method comprises the following steps: i') essentially activating xenoamicin BGC in said bacterium, and ii') optionally deleting a CyaA gene in said bacterium; and the method further comprises: iii) expressing in said bacterium at least one positive selectable marker gene and at least one negative selectable marker gene; wherein deleting a CyaA gene of steps i) or i') comprises introducing in said bacterium at least one CyaA specific siRNA, or a group of comprising a Cas gene, at least one CyaA specific crRNA array, a pair of GR specific homology regions left and right; ; and/or wherein activating xenoamicin BGC of steps i) or i') comprises introducing in said bacterium a group of sequences comprising a Cas gene, at least one xenoamicin BGC specific crRNA array, a pair of xenoamicin BGC specific homology regions left and right, a promoter system sequence, and optionally an enhancer sequence. Rupshomycin derivatives Another aspect of the present invention is directed to rupshomycin and its derivatives discovered and obtained by the inventive methods described herein. Said compounds (see Figures 12 – 14, and 23 – 25) are the produc of a novel BGC named rpmA-O and exhibit interesting biological activities. Therefore, thee compounds are particularly useful as aantibiotic, or anti-drug, or immune suppressive drug. Thus, the present invention is also directed to a compound of general formula (I)

wherein GAR-P04397WO09 Application (final)2.docx Y represents –CH=CH₂ or R¹, R², R³, R⁴, and R⁵ are independently of each other selected from –H, –NH₂, –NHR⁶, –F, –OH, –OCH₃, –OCH₂CH₃, and –OCH₂CH₂CH₃; or R² and R³ or R³ and R⁴ together with the carbon atom to which they are bound to form one of the rings:

wherein R⁶ represents –H, –CH3, –CH2CH2CH3, –CH(CH3)2, –CH2(CH2)2CH3, –CH2(CH2)3CH3, –CH2(CH2)4CH3, –CH2(CH2)5CH3, –CH2(CH2)6CH3, –CH2(CH2)7CH3, –CH2(CH2)8CH3, –CH2(CH2)9CH3, –CH2(CH2)10CH3, –CH2(CH2)11CH3, –CH2(CH2)12CH3, –CH2CH(CH3)2, –C(CH3)3, –CH2CH=CH2, –CH2CH=CH(CH3), –CH2CH=C(CH3)2, or –CH2CH=CHCH2CH3; with the proviso that when Y represents –CH=CH2, R¹, R², R⁴, and R⁵ cannot be – H, and R³ cannot be –OH simultaneously. The structural fragment

indicates a mixture of cis and trans isomers. In a prefeferred embodiment, the rupshomycin compounds are in a (2Z)- thiazolidine isomer form of formula (IA)

wherein Y represents –CH=CH2 or

R¹, R², R³, R⁴, and R⁵ are independently of each other selected from –H, –NH2, –NHR⁶, –F, –OH, –OCH3, –OCH2CH3, and –OCH2CH2CH3; or R² and R³ or R³ and R⁴ together with the carbon atom to which they are bound to form one of the following rings: GAR-P04397WO09 Application (final)2.docx with the proviso that when Y represents –CH=CH2, R¹, R², R⁴, and R⁵ cannot be – H, and R³ cannot be –OH simultaneously. In a prefeferred embodiment, the rupshomycin compounds are in a (2E)- thiazolidine isomer form of formula (IB)

wherein Y represents –CH=CH2 or

R¹, R², R³, R⁴, and R⁵ are independently of each other selected from –H, –NH₂, –NHR⁶, –F, –OH, –OCH₃, –OCH₂CH₃, and –OCH₂CH₂CH₃; or R² and R³ or R³ and R⁴ together with the carbon atom to which they are bound to form one of the

GAR-P04397WO09 Application (final)2.docx with the proviso that when Y represents –CH=CH2, R¹, R², R⁴, and R⁵ cannot be – H, and R³ cannot be –OH simultaneously.

39 40 GAR-P04397WO09 Application (final)2.docx Particularly preferred is when the compound of the above shown group is a (2E)- thiazolidine isomer. Particularly preferred is when the compound of the above shown group is a (2Z)- thiazolidine isomer. GAR-P04397WO09 Application (final)2.docx Table 2: Strains and plasmids used in this study. Strains Genotype Source/Reference E. coli ST18 pro thi hsdR⁺ Tp^r Sm^r; chromosome::RP4-2 DSMZ, DSM No.: 22074 Tc::Mu-Kan::Tn7/λpir; ΔhemA E. coli DH10B F^–mcrA Δ(mrr-hsdRMS-mcrBC) φ80lacZΔM15 Invitrogen ΔlacX74 recA1 endA1 araD139 Δ(ara-leu)7697 galU galK λ^–rpsL(Str^R) nupG P. laumondii subsp. Wild type DSMZ, DSM No.: 15139 laumondii TTO1 X. nematophila ATCC Wild type ATCC 19061 19061 X. doucetiae FRM16 Wild type DSMZ, DSM No.: 17909 X. indica DSM 17382 Wild type Xenorhabdus sp. TS4 Wild type Plasmid pEB17 pDS132 based, R6K ori, oriT, kanR, cipB, sacB pCEP_kan pDS132 based, R6K ori, oriT, kanR, araC, P_BAD pTargetF pMB1 Spec^R sgRNA-cadA Addgene plasmid # 62226 p46Cpf1-OP2 repA101(Ts) cat tetR Ptet-Red araC PBAD codon Addgene # 98592 optimized FnCas12a pAR14 pMB1 Spec^R sacB This study pAR15 pMB1 Gm^R sacB This study pAR16 p15A cat tetR Ptet-Red araC PBAD codon This study optimized FnCas12a pAR18 pMB1 Gm^R sacB crRNA framework This study pAR20 pSeva231 tetR Ptet-Red araC PBAD codon This study optimized FnCas12a sacB crRNA framework pDS132 R6K ori, mob RP4, cat, sacB, sacB promoter, Genbank AY489048 lac operator pMB1 - GenBank: M77789.2 repA101(Ts) - GenBank: K00042.1 p15A - GenBank: V00309.1 pSeva231 pBBR1 oriV, RK2 oriT, kanR pAR29bad p15A oriV, RK2 oriT, kanR, araC^AM, PBAD pAR30bad pBBR1 oriV, RK2 oriT, Gm^R pCola_PBad_ xscA-H PBAD promoter, pCOLA ori, xscA-H This work pACYC_PBad_xscIJ PBAD promoter, pACYC ori , xscIJ This work pCDF_PBad_xscK PBAD promoter, pCloDF13 ori, xscK This work pCola pCOLA ori, KmR Novagen pACYC pACYC ori, CmR Novagen pCDF-1b pCloDF13 ori, SmR Novagen Legend: KanR: kanamicin resistance, Spec^R: Spectinomycin resistance; Gm^R: gentamicin resistance, cipB promoter pEB17, pCEP_kan disclosed by Nat. Chem.14, 701–712 (2022). GAR-P04397WO09 Application (final)2.docx Table 3: Overview of performed experiments of genome editing in P. laumondii TTO1 and X. nematophila to

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pb ^k ³ _. 1eh ^ty b s m_r ayg l^oo mo hnee w_te becneuqe ^sdec a_lpe ^reh ^ts d e_t e a ⁿ _i c_id ^m _r n ^{i e} _t * e d GAR-P04397WO09 Application (final)2.docx Table 4: Proteins of the mxn cluster in X. nematophila ATCC 19061, their proposed function, protein size and closest homologues. Protein Locus Size (aa) Proposed function MxnA XNC1_RS07585 81 acyl carrier protein MxnB XNC1_RS07580 408 beta-ketoacyl-ACP synthase MxnC XNC1_RS07575 411 HMG-CoA synthase-like protein MxnD XNC1_RS20555 262 enoyl-CoA hydratase MxnE XNC1_RS07565 250 enoyl-CoA hydratase MxnF XNC1_RS07560 1980 PKS MxnG XNC1_RS07555 2407 Mixed trans-AT type I PKS/NRPS MxnH XNC1_RS07550 2302 NRPS MxnI fabD 286 Acyltransferase MxnJ XNC1_RS07540 400 major facilitator superfamily transporter MxnK XNC1_RS07535 229 thioesterase MxnL XNC1_RS07530 664 BkdA MxnM XNC1_RS22760 4823 hybrid PKS/NRPS MxnN XNC1_RS07520 2344 PKS type I MxnO XNC1_RS07515 529 ATPase component of ABC transporters Table 5: Proteins of the rpm cluster in X. indica DSM 17382, their proposed function, protein size and closest homologues. Gene NCBI Gene Protein NCBI Proposed function of corresponding Gene Accession No. size (bp) Accession No. protein rpmA Xind_RS13800 795 WP_047680461.1 Aldolase rpmB Xind_RS13805 1659 WP_187650276.1 Acyl-CoA ligase rpmC Xind_RS13810 429 WP_246432556.1 OsmC family protein rpmD Xind_RS13815 7839 WP_187650277.1 PKS-NRPS hybrid rpmE Xind_RS13820 4305 WP_047680469.1 NAD(P)-dependent oxireductase (PKS) rpmF Xind_RS13825 6024 WP_187650278.1 Alpha/beta fold hydrolase (PKS) rpmG Xind_RS13830 1485 WP_052189457.1 4-hydroxyphenylacetate 3-hydroxlyase rpmH Xind_RS13835 1344 WP_047680471.1 MATE family efflux transporter rpmI Xind_RS13840 366 WP_047680473.1 Hypothetical protein rpmJ Xind_RS13845 1224 WP_187650279.1 3-dehydroquinate synthase rpmK Xind_RS13850 768 WP_187650280.1 Alpha/beta fold hydrolase rpmL Xind_RS13855 861 WP_052189461.1 ACP S-malonyltransferase rpmM Xind_RS13860 1035 WP_047680476.1 Cupin domain-containing protein rpmN Xind_RS13865 612 WP_222941817.1 SAP domain-containg protein rpmO Xind_RS13870 459 WP_047680486.1 Gyrl-like domain-containing protein Table 6: Proteins of the xsc cluster (safracin) in Xenorhabdus sp. TS4, their proposed function, protein size and closest homologues. Protein NCBI Reference Sequence Size (aa) Proposed function XscA Xets_RS15840 1055 non-ribosomal peptide synthetase XscB Xets_RS15835 1073 non-ribosomal peptide synthetase XscC Xets_RS15830 1444 non-ribosomal peptide synthetase XscD Xets_RS15825 352 putative hydroxylase GAR-P04397WO09 Application (final)2.docx XscE Xets_RS15820 66 MbtH family NRPS accessory protein XscF Xets_RS15815 355 O-methyltransferase XscG Xets_RS15810 343 O-methyltransferase XscH Xets_RS15805 180 dihydrofolate reductase/ dehydratase XscI Xets_RS15845 220 SAM-dependent methyltransferase XscJ Xets_RS15850 501 FAD-dependent monooxygenase XscK Xets_RS24810 512 metallopeptidase Table 7: Sequences used in this study (sequences present in the Sequence Listing file). Table 7a Primers ID Name Target gene/template Direction NO 1 AR533 pAR20 or pCpf1-XP fw NO 2 AR534 pAR20 or pCpf1-XP rev NO 3 PC O45 XDOUV2_01760, CyaA fw NO 4 PC O46 XDOUV2_01760, CyaA rv NO 5 PC O47 XDOUV2_01760, CyaA fw NO 6 PC O48 XDOUV2_01760, CyaA rv NO 7 PC O49 XDOUV2_01760, CyaA fw NO 8 PC O50 XDOUV2_01760, CyaA rw TT01_PLUMV2_22995 NO 9 PC O69 (CyaA) fw TT01_PLUMV2_22995 NO 10 PC O70 (CyaA) rw TT01_PLUMV2_22995 NO 11 PC O71 (CyaA) fw TT01_PLUMV2_22995 NO 12 PC O72 (CyaA) rw TT01_PLUMV2_22995 NO 13 PC O73 (CyaA) fw TT01_PLUMV2_22995 NO 14 PC O74 (CyaA) rw NO 15 ODA1 XDOUV2_10775(XabA) fw NO 16 ODA2 XDOUV2_10775 (XabA) rv NO 17 ODA3 XDOUV2_10775 (XabA) rv NO 18 VPpCEP-fw pCEP_Kan fw NO 19 VPpDS132-rv pCEP_kan rv NO 20 AR426 p46Cpf1-OP2 fw NO 21 AR427 p46Cpf1-OP2 rev NO 22 AR428 p15A vector fw NO 23 AR429 p15A vector rev NO 24 AR430 pTargetF fw NO 25 AR431 pTargetF rev NO 26 AR432 sacB (pEB17_KM) fw NO 27 AR433 sacB (pEB17_KM) rev NO 28 AR434 pSEVA631 fw NO 29 AR435 pSEVA631 rev NO 30 AR436 pAR15 fw NO 31 AR437 pAR15 rev GAR-P04397WO09 Application (final)2.docx NO 32 AR_seq_07 Pex_gxpS_TTO1 fw NO 33 AR_seq_08 Pex_gxpS_TTO1 rev NO 34 AR_seq_11 Pex_indC fw NO 35 AR_seq_12 Pex_indC rev NO 36 AR_seq_13 dgxpS_TTO1 fw NO 37 AR_seq_14 dgxpS_TTO1 rev NO 38 AR_seq_17 dstlA fw NO 39 AR_seq_18 dstlA rev NO 40 AR_seq_21 Pex_glb fw NO 41 AR_seq_22 Pex_glb rev NO 42 AR_seq_29 drxp fw NO 43 AR_seq_30 drxp rev NO 44 AR_seq_31 dxcnA fw NO 45 AR_seq_32 dxcnA rev NO 46 AR_seq_33 Pex_rxpA fw NO 47 AR_seq_34 Pex_rxpA rev NO 48 AR_seq_35 Pex_xcnA fw NO 49 AR_seq_36 Pex_xcnA rev NO 50 AR_seq_37 Pex_mxnA_XNEM fw NO 51 AR_seq_38 Pex_mxnA_XNEM rev NO 52 AR_seq_76 Pex_stlA fw NO 53 AR_seq_77 Pex_stlA rev NO 54 AR_seq_84 Xnem_C7.2.Pex fw NO 55 AR_seq_85 Xnem_C7.2.Pex rev NO 56 AR577 PvanCC promoter fw NO 57 AR606 rpmA fw NO 58 AR607 rpmA rev NO 59 AR608 rpmJ fw NO 60 AR609 rpmJ rev NO 61 AR620 rpmG fw NO 62 AR621 rpmG rev NO 63 AR616 rpmMN fw NO 64 AR617 rpmMN rev NO 65 AR604 rpmO fw NO 66 AR605 rpmO rev NO 201 AR_seq_86 XNEM_hfq fw NO 202 AR_seq_87 XNEM_hfq rev NO 203 AR_seq_88 XNEM_cyaA fw NO 204 AR_seq_89 XNEM_cyaA rev NO 205 AR_seq_90 Pex_dpr fw NO 206 AR_seq_91 Pex_dpr rev NO 207 XDUO_cyaA fw NO 208 XDUO_cyaA rev NO 209 XDUO_Pex_xab fw NO 210 XDUO_Pex_xab rev NO 211 clxD (codon optimized) styA (Bacillus) NO 212 *T1- ^A GAR-P04397WO09 Application (final)2.docx Table 7b: Gene specific target spacers used for CRISPR/Cas12 mediated genome editing (the PAM sequence is present in the genome closed to TS) Target SEQ ID spacer Gene Type of editing PAM sequence NO 67 TS-A TTTG stlA deletion NO 68 TS-B TTTA NO 69 TS-A TTTA stlA promoter exchange NO 70 TS-B TTTG NO 71 TS-A TTTG gxpS deletion NO 72 TS-B TTTG NO 73 TS-A TTTA gxpS promoter exchange NO 74 TS-B TTTG NO 75 TS-A TTTG xcnA deletion NO 76 TS-B TTTC NO 77 TS-A TTTC xcnA promoter exchange NO 78 TS-B TTTG NO 79 TS-A TTTA rxpA-C deletion NO 80 TS-B TTTA NO 81 TS-A TTTC rxpA promoter exchange NO 82 TS-B TTTA NO 83 TS-A Fluorescent repor TTTC rxpA-C ter NO 84 TS-B replacement TTTC NO 85 TS-A TTTA indC promoter exchange NO 86 TS-B TTTC NO 87 TS-A TTTA glbA promoter exchange NO 88 TS-B ATTA NO 89 TS-A TTTA mxnA refactoring NO 90 TS-B TTTC NO 91 TS-A TTTA mxnB promoter exchange NO 92 TS-B TTTG NO 93 TS-A TTTC mxnL promoter exchange NO 94 TS-B TTTG NO 95 TS-A Fluoresce TTTG stlCDE nt reporter NO 96 TS-B replacement TTTA NO 97 TS-A ppyS Fluorescent reporter TTTA NO 98 TS-B PluTT01m_24855 replacement TTTC NO 99 TS-A F TTTA AQ MT4 luorescent reporter NO 100 TS-B replacement TTTG NO 101 TS-A Fl TTTA ppyS uorescent reporter NO 102 TS-B replacement TTTC NO 103 TS-A Fluo TTTA odlC rescent reporter NO 104 TS-B replacement TTTC NO 105 TS-A I Bidir TTTC xscA/ ectional promoter NO 106 TS-B exchange TTTC NO 107 TS-A Deletio TTTC xscK n/promoter NO 108 TS-B exchange TTTG NO 109 TS-A TTTG rpmA promoter exchange NO 110 TS-B TTTC NO 111 TS-A TTTG rpmD promoter exchange NO 112 TS-B TTTC GAR-P04397WO09 Application (final)2.docx NO 113 TS-A TTTC rpmG Deletion NO 114 TS-B TTTC NO 115 TS-A TTTC rpmM-O Deletion NO 116 TS-B TTTA NO 117 TS-A TTTC hfq X. indica Deletion NO 118 TS-B TTTA N^{O 191 TS-A} _{hfq X.} TTTG nematophil Deletion NO 192 TS-B a TTTC NO 193 TS-A cyaA X. TTTA nem Deletion NO 194 TS-B atophila TTTA NO 195 TS-A TTTG dprA promoter exchange NO 196 TS-B TTTC NO 197 TS-A TTTA cyaA_XDUO Deletion NO 198 TS-B TTTG NO 199 TS-A TTTC xabA promoter exchange NO 200 TS-B TTTA Table 7c Sequence list of synthetic dsDNA fragments used for CRISPR/Cas12 mediated genome editing SEQ ID Name

Type of Editing /Description

crRNA PJ23119, crRNA leader, direct repeat, spacer- NO 119 framework dummy (BsaI sites), direct repeat, terminator Adapter with BsaI site, [selected target spacer (23-31 bp)], direct repeat, TERMINATOR, placeholder (lowercase), [homologues region HA-L (up to 500 bp)], GS-linker sequence I, Adapter NO 120 dummy Fluorescent reporter with BsaI site Adapter with BsaI site, [selected target spacer (23-31 bp)], direct repeat, TERMINATOR, HA-L placeholder (lowercase), [homologues region NO 121 dummy Deletions (up to 500 bp)], Adapter with BsaI site Adapter with BsaI site, [selected target spacer (23-31 bp)], direct repeat, TERMINATOR, HA-L placeholder (lowercase), [homologues region NO 122 dummy Promoter exchange (up to 500 bp)], Adapter with BsaI site Adapter with BsaI site, [selected target spacer (23-31 bp)], direct repeat, TERMINATOR, placeholder (lowercase), [homologues region HA-L Promoter exchange with (up to 500 bp)], proD-UTR(reversed), Adapter NO 123 dummy Bidirectional Promoter (proD) with BsaI site dsDNA dsDNA Fragment for Fluorescent BsaI site, GS-linker sequence II,[Insertion site NO 124 Fragment reporter editing for Fluorescent Reporter Sequence] BsaI site Adapter with BsaI site, [homologues region (up to 500 bp)], placeholder (lowercase), PJ23119, HA-R crRNA-leader, direct repeat, [selected target NO 125 Dummy Fluorescent reporter spacer (23-31 bp)], Adapter with BsaI site Adapter with BsaI site, [homologues region (up HA-R to 500 bp)], placeholder (lowercase), PJ23119, NO 126 Dummy deletion crRNA-leader, direct repeat, [selected target GAR-P04397WO09 Application (final)2.docx spacer (23-31 bp)], Adapter with BsaI site Adapter with BsaI site, [Start-codon (ATG) with homologues region (up to 500 bp)], placeholder (lowercase), PJ23119, crRNA-leader, direct repeat, HA-R [selected target spacer (23-31 bp)], Adapter NO 127 Dummy promotor exchange with BsaI site Adapter with BsaI site, [Start-codon (ATG) with homologues region (up to 500 bp)], placeholder (lowercase), P_J23119, crRNA-leader, direct repeat, HA-R promotor exchange with [selected target spacer (23-31 bp)], Adapter NO 128 Dummy translational enhancer with BsaI site NO 129 FnCas12a Codon Optimized mNeonGree NO 130 n Fluorescen Reporter Sequence BsaI site, terminator (reverse), vanR-AM CDS PvanCC (reverse), van2 RBS and P_J23100, terminator NO 131 modified VA- Inducible Promoter (reverse), PvanCC, RiboJ, B0064 RBS, BsaI site Adapter with BsaI site, terminator (reverse), spacing bases, vanR-AM CDS (reverse), van2 RBS and P_J23100, spacing bases, terminator (reverse), spacing P_vanCC modified for T7 bases, P_vanCC, RiboJ, T7-g10 translational NO 132 PvanCC _ T7 Translational enhancer enhancer part, Adapter with BsaI site NO 133 ProD* Bidirectional Promoter C106G, Davis et. al 2011 BsaI site, terminator (reverse, spacing bases, P_tac, RiboJ, spacing bases, B0064 RBS, spacing NO 134 Ptac Ptac_Promoter alone bases, BsaI site Enhancer , Poly-A, RBS Olins PO, Rangwala SH.; A novel sequence element derived from bacteriophage T7 mRNA acts as an enhancer of translation of the lacZ gene in Escherichia coli. J Biol Chem.1989 Oct NO 135 T7g10 & RBS T7g10 = Translational Enhancer 15;264(29):16973-6. BsaI site, terminator (reverse), spacing bases, lacI-AM CDS (reverse), ara1 RBS and P_J23100, spacing bases, terminator (reverse), spacing bases, Ptac, RiboJ, spacing bases, B0064 RBS, BsaI NO 136 Ptac_mod modified Ptac Promoter site Homology arm left for ΔstlA NO 137 ΔstlA_L deletion Homology arm right for ΔstlA NO 138 ΔstlA_R deletion Homology arm left for stlA- NO 139 stlA_L Promoter exchange Homology arm right for stlA- NO 140 stlA_R Promoter exchange Homology arm left for ΔgxpS NO 141 ΔgxpS_L deletion Homology arm right for ΔgxpS NO 142 ΔgxpS_R deletion GAR-P04397WO09 Application (final)2.docx Homology arm left for gxpS- NO 143 gxpS_L Promoter exchange Homology arm right for gxpS- NO 144 gxpS_R Promoter exchange Homology arm left for ΔxcnA NO 145 ΔxcnA_L deletion Xenorhabdus nematophila Homology arm right for ΔxcnA NO 146 ΔxcnA_R deletion Homology arm left for xcnA NO 147 xcnA_L Promoter exchange Homology arm right for xcnA NO 148 xcnA_R Promoter exchange Homology arm left for ΔrxpA-C NO 149 ΔrxpA-C_L deletion Homology arm right for ΔrxpA-C NO 150 ΔrxpA-C_R deletion Homology arm left for ΔrxpA-C NO 151 rxpA-C_L Promoter exchange Homology arm right for ΔrxpA-C NO 152 rxpA-C_R Promoter exchange Homology arm left for Fluorescent reporter NO 153 rxpA-C_L replacement of rxpA-C Homology arm right for Fluorescent reporter NO 154 rxpA-C_R replacement of rxpA-C Homology arm left for indC NO 155 indC_L promoter exchange Homology arm right for indC NO 156 indC_R promoter exchange Homology arm left for promoter NO 157 glbA_L exchange of glbA Homology arm right for promoter NO 158 glbA_R exchange of glbA Homology arm left for mxnB NO 159 mxnB_L Promoter exchange Homology arm right for mxnB NO 160 mxnB_R Promoter exchange Homology arm left mxnK NO 161 mxnK_L Promoter exchange Homology arm right for mxnK NO 162 mxnK_R Promoter exchange Homology arm left for stlCDE Fluorescent reporter NO 163 stlCDE_L replacement Homology arm right for stlCDE Fluorescent reporter NO 164 stlCDE_R replacement Homology arm left for ppyS Fluorescent reporter NO 165 ppyS_L replacement PluTT01m_24855 GAR-P04397WO09 Application (final)2.docx Homology arm right for ppyS Fluorescent reporter NO 166 ppyS_R replacement PluTT01m_24855 Homology arm left for xscA/xscI NO 167 xscA/xscI_L Promoter exchance/Refactoring Xenorhabdus sp. TS4_R Homology arm right for xscA/xscI NO 168 xscA/xscI_R Promoter exchance/Refactoring Xenorhabdus sp. TS4 Homology arm left for xscKΔxscH NO 169 xscKΔxscH_L Promoter exchange /Refactoring Xenorhabdus sp. TS4 Homology arm right for xscKΔxscH xscKΔxscH Promoter NO 170 _R exchance/Refactoring Xenorhabdus sp. TS4 Homology arm left for rpmA NO 171 rpmA_L Promoter exchange Xenorhabdus indica Homology arm right for rpmA NO 172 rpmA_R Promoter exchange Xenorhabdus indica Homology arm left for rpmD NO 173 rpmD_L Promoter exchange Xenorhabdus indica Homology arm right for rpmD NO 174 rpmD_R Promoter exchange Xenorhabdus indica Homology arm left for ΔrpmG NO 175 ΔrpmG_L deletion Xenorhabdus indica Homology arm right for ΔrpmG NO 176 ΔrpmG_R deletion Xenorhabdus indica Homology arm left for ΔrpmM-O NO 177 ΔrpmM-O_L deletion Xenorhabdus indica Homology arm right for ΔrpmM- NO 178 ΔrpmM-O_R O deletion Xenorhabdus indica Homology arm left for Δhfq NO 179 Δhfq_L deletion Xenorhabdus indica NO 180 Δhfq_R Homology arm right for Δhfqv Xenorhabdus indica Homology arm left for Δhfq NO 181 Δhfq_L deletion Xenorhabdus nematophila Homology arm right for Δhfq NO 182 Δhfq_R deletion Xenorhabdus nematophila Homology arm left for ΔcyaA NO 183 ΔcyaA_L deletion Xenorhabdus nematophila Homology arm right for ΔcyaA NO 184 ΔcyaA_R deletion Xenorhabdus nematophila Homology arm left for activating NO 185 dprA_L dprA by promoter exchange Xenorhabdus nematophila Homology arm right for activating dprA by promoter NO 186 dprA_R exchange Xenorhabdus nematophila Homology arm left for ΔcyaA NO 187 ΔcyaA_L deletion Xenorhabdus doucetiae Homology arm right for ΔcyaA NO 188 ΔcyaA_R deletion Xenorhabdus doucetiae Homology arm left for activating NO 189 xabA_L xabA by promoter exchange Xenorhabdus doucetiae GAR-P04397WO09 Application (final)2.docx Homology arm right for activating xabA by promoter NO 190 xabA_R exchange Xenorhabdus doucetiae Table 9: Chemical structures of benzoic acid (BA) derivatives and rupshomycin compounds 19-25 (Figure 12) 3,4-amino-4-hydroxy benzoic acid (3,4-AHBA) 3,4-dihydroxybenzoic acid (3, 4- DHBA) vanillic acid 19 backbone for 20-24 R= 20 R= 21 / 34 R= 2_{2 / 32} ^{R= 23 / 31} GAR-P04397WO09 Application (final)2.docx O S N H HO R= NH₂ 2^{4 / 37} _{25 / 33} Table 10: structures of described compounds OH OH I_{sopropylstillbene (1)} ^{Indigoidine (2)} O 1 HN R OH N O H O H NH HN O N O N O H NH HN O N O O H R2 Glidobactins GameXPeptideA (3) (4): R¹=OH, R²=H; (5): R¹=OH, R²=Me; Xenortide A Xenocoumacin I (7) 9: R¹=iBu, R²= iPr, R³=Me, R⁴= iPr; 10: R¹=iPr, R²= iPr, R³=H, R⁴= iPr; Xenocoumacin II (8) 11: R¹=iPr, R²= iBu, R³=Me, R⁴= iPr; GAR-P04397WO09 Application (final)2.docx GAR-P04397WO09 Application (final)2.docx Demethoxypuromycin (27) N-Acetyl-demethoxypuromycin (28) N N N H O N O N O_NH O ^OH NH N-formyl-demethoxypuromycin (29) Table 11: List of fluorescent proteins with key parameters. Values for excitation/emission maxima (λ_ex, λ_em) were taken from www.fpbase.org Protein λ_ex λ_em [nm] Characteristics Fbbase ID [nm] (www.fpbase.org) mTagBFP2 399 454 monomeric ZO7NN sfGFP 485 510 monomeric, fast B4SOW (superfolded GFP) maturation mNeonGreen 506 517 monomeric, ZRKRV superior brightness GAR-P04397WO09 Application (final)2.docx mGold 515 531 monomeric, UNETX bright, suitable for FACS mScarlet-I 569 593 monomeric, high 6VVTK brightness mCherry 587 610 faster maturation ZERB6 than mScarlet-I, but less bright Description of the Figures Figure 1 shows A) an overview of the method described herein to identify global regulators comprising replacement of at least two constitutively expressed BGCs by two different fluorescent reporters, followed by transposon mutagenesis and analysis for loss of fluorescence for both reporters. Non-fluorescent mutants are identified, isolated and then analysed by whole-genome sequencing to identify global regulators. Non-fluorescent mutants are also screened for the production of Natural Products by HPLC/MS analysis. B) Schematic of pAR20 plasmid with crRNA frameworks and elements for fluorescent reporter replacement, and of cloning of synthetic dsDNA fragments harboring the repair template and target spacer together with a fluorescent reporter sequence into the synthetic crRNA framework encoded on pAR20. C) Schematic of pAR20 plasmid with crRNA frameworks, synthetic dsDNA fragments, and elements for cluster activation, DR: direct repeat. D) Schematic representation of an mass spectroscopy (MS) chromatograms according to expected process: deletion of a global regulator with subsequent activation of a selected secondary metabolite. 1) Wild type (WT) strain with complex metabolite profile; 2) after deletion of a global regulator the metabolite profile becomes clearer; 3) Exchange/replacement of native secondary metabolite promotor by an inducible promotor in the global regulator deletion background; 4) targeted induction of the desired secondary metabolite. Figure 2 shows design of genome editing based on a two plasmid system in Photorhabdus using stlA deletion as an example. A) Phenotypic comparison of wild type (WT) and ^stlA deletion mutant; B) Role of StlA in the biosynthesis of isopropylstilbene (1). C) Schematic representation of the selection of target spacer and homology arms. D) schematic GAR-P04397WO09 Application (final)2.docx cloning of synthetic dsDNA fragments harboring the repair template and target spacer into synthetic crRNA framework encoded on pAR18; detailed genotype of pAR18 is shown in Table 1. The figure was created with BioRender.com. Figure 3 shows A) schematic representation of pAR20 plasmid that can be used for genome editing with CRISPR/Cpf1 approach digested with BsaI. B) Overview of the developed single plasmid CRISPR-Cpf1 genome editing workflow, e.g. for BGC activation and/or global regulator deletion. The approach starts with conjugation of the target specific pAR20 into the strain to be edited (with or without previous global regulator (GR) deletion, day 1); selection of conjugates and induction of CRISPR/Cpf1 components followed by selection of correct edited strains (day 3); plasmid curing with sucrose (day 5); screening for new or known compounds (day 6); entering a new editing cycle (day 7). Figure created with BioRender.com. Figure 4 shows overview of MS spectra of deletion mutants. A) Base peak chromatograms (BPC) of P. laumondii TTO1 wild type and deletion mutants. B) BPCs of X. nematophila wild type and deletion mutants. Figure 5 shows gel electrophoresis images of deletion and promoter exchange mutants after colony PCR. Figure 6 shows single plasmid CRISPR/Cpf1 genome editing method for promoter exchange upstream of indC. A) Schematic representation of target spacer and homology arms selection; B) schematic cloning of synthetic dsDNA fragments harboring the repair template and target spacer and the vanillic acid promoter sequence into synthetic crRNA framework encoded on pAR20. C) Schematic representation of the genome editing approach mediated by pAR20; the sequence between the homology arms are replaced by the promoter sequence; detailed genotype of pAR20 can be found in Table 1. D) Phenotypic comparison of induced and non-induced mutants (VA = vanillic acid). E) Structure of indigoidine (2). The figure was created with BioRender.com. Figure 7 shows overview of MS spectra of induced (solid line) and non-induced (dashed line) cultures after successful promoter exchanges. A) GAR-P04397WO09 Application (final)2.docx Chromatograms of P. laumondii TTO1 and edited mutants; wild type (WT) BPC and for better visualization extracted ion chromatograms (EICs) representing major derivatives of associated NPs. B) Chromatograms of Xenorhabdus nematophila wild type and genome edited mutants. Structures are shown in Tables 9 and 10. Figure 8 shows strain engineering towards madumycin production in X. nematophila. A) Putative madumycin BGC mxn; B) Cluster refactoring; replacing of native promoters PmxnA and PmxnB by insertion by the PvanCC promoter at different positions and insertion of genetic parts like insulators riboJ51 and ribosomal binding sites. C) Putative biosynthesis of 16 by the mxn encoded assembly line. A: adenylation domain, C: condensation domain, CY: cyclization domain, E: epimerization domain, MT: methylation domain, PCP: peptidylcarrier protein domain, ACP (small black circle): acyl carrier protein domain, KS: β-ketoacyl carrier protein synthase domain, KR: ketoreductase domain, DH: dehydratase domain, OX: oxidation domain, TE: thioesterase domain. D) HPLC/MS chromatograms of “re”-engineered mxn cluster strains; BPC (black), EIC for 16 (504.2 m/z [M+H]+,red), induced (solid line) and non-induced (dashed line). Figure 9 shows structure elucidation and proposed biosynthesis pathway of the formation of madumycin II (16) in X. nematophila. A) Three different promotor exchange constructs and EICs for 16 (504.2 m/z [M+H]⁺) of induced cultures. B) HR-MS spectrum for 1; HR-MS spectrum for 1 after addition of L-alanine-D4; HR-MS spectrum for 1 after addition of D8-L- valine. C) MS/MS fragmentation comparison of produced compound 16 and its chemical standards. Figure 10 shows A) the xsc BGC responsible for the production of safracin A (SAC-A, 2) and safracin B (SAC-B, 1) in Xenorhabdus sp. TS4. B) shows strains I – III and corresponding EICs for SAC-A and SAC-B production; I: wild type stain with silent xsc BGC; II: Bidirectional promoter exchange between xscA and xscJ, production of SAC-A and B; III: Additional promoter exchange upstream of xscK while deleting xscH; producing SAC-B exclusively. C) Biosynthetic pathway of SAC-A and B. GAR-P04397WO09 Application (final)2.docx Figure 11 shows A) semisynthesis overview to produce ecteinascidin 743 and (-)-Jorumycin starting from safracin B; B) comparison of SAC-B production in Xenorhabdus sp. TS4 and E. coli LZ84 harboring different plasmids encoding the xsc BGC. Figure 12 shows stepwise activation and characterization of the rupshomycin biosynthetic gene cluster (rpm). I: native and silent BGC rpm under laboratory conditions. II: PvanCC promoter exchange upstream of rpmA, no production observed after induction. III: PvanCC promoter exchange upstream of rpmD, no production observed after induction. IV: promoter exchange upstream of rpmA with exchange of the intergenic region between rpmC and rpmD by RiboJ51 and T7g10 UTR, production of 19 observed after induction. V: Ptac promoter exchange upstream of rpmA with exchange of the intergenic region between rpmC and rpmD by RiboJ51 and T7g10 UTR; feeding of several benzoic acid derivatives (all 1mM) leading to the production of compounds 20 – 24 after induction. VI: strain V with deletion of rpmG, conjugated with expression vector expressing rpmA and rpmJ; detection of compound 25 after induction. VII: strain V with deletion of rpmMNO and feeding of 3,4- AHBA; no production observed, culture dies after induction. VIII: strain VII conjugated with expression vector expressing rpmM and rpmN. IX: strain VII conjugated with expression vector expressing rpmO. In strains V-IX, in addition to promoter exchange, the global regulator Hfq was also deleted. Figure 13 A) Overexpression of rpmA and rpmG encoded on pAR29badad revelead 3-amino-4-hydroxy benzoic acid (3,4-AHBA) as natural starting unit for rpm BGC. B) Biosynthetic gene cluster for the formation of rupshomycin (26) and derivatives thereof. C) Putative biosynthetic pathway for rupshomycin (26) and derivatives 31 and 33. Hydroxylation in 5-position is catalyzed by rpmG (shaded); Removal of 3 amino group is catalyzed by RpmB and RpmM in the presence of Trp; C: condensation domain, CY: cyclization domain, PCP: peptidylcarrier protein domain, ACP (small black circle): acyl carrier protein domain, KS: β-ketoacyl carrier protein synthase domain, KR: ketoreductase domain, DH: dehydratase domain, TE: thioesterase domain. GAR-P04397WO09 Application (final)2.docx Figure 14 Growth curves recorded with the Tecan Sparc microtiter plate reader, 100 µl culture in a 96 well microtiter plate over 24 hours for X. indica strains producing rupshomycin derivatives. Addition of the inducer and benzoic acid was added from the start. The numbering I - IX corresponds to the strains in Figure 12. A: growth of strain I culture with and without induction (1mM IPTG), with and without addition of 3,4- AHBA. B: growth of strain V culture with and without induction, with and without addition of 3,4-AHBA. C: growth of strain I culture with and without induction, with and without addition of 3,4-DHBA. D: growth of strain V culture with and without induction, with and without addition of 3,4-DHBA. E: growth of induced and 3,4-AHBA supplemented strain VIII culture with vector expressing rpmMN or empty expression vector. F: growth of induced and 3,4-AHBA supplemented strain IX culture with vector expressing rpmO or empty expression vector. Figure 15A) shows schematic representation of the high-throughput genome editing approach using microtiter plates. Overnight cultures grown in a deepwell plate are diluted 1:25 in 100 µl and transferred to a 96 well microtiter plate. Cultures are incubated in a microplate reader at 30 °C while growth is recorded. After the CRISPR procedure, two dilutions are prepared and transferred to selection plates using a multichannel pipette. Single colonies can be tested for successful genome editing after two days. B) shows an example of a 7X7 patches spotted with the ROTOR⁺ from Singer Instruments. Figure 16shows spotting and plating of CRISPR cultures. Plate with edited colonies after 2 days of incubation. A) Place the square agar plate at an angle of about 45°. B) Using a 12 channel pipette, add 20 µl to the upper end of the plate and allow the drops to run to the lower end without running into each other. C) Plates with cultures of different dilutions after two days of regeneration. Figure 17 A) shows fluorescence imaging of pigmented Photorhabdus luminescens TTO1 indicator strains. Strains were constructed using the CRISPR-Cas12 approach described in this patent. In these strains, BGCs stlCDE, ppyS, AQ MT were replaced by an mNeonGreen gene. Strains were spotted onto LB agar plates and imaged at different days using an automated Leica Thunder Imager stereo microscope. Selected GAR-P04397WO09 Application (final)2.docx indicator strains develop fluorescence over time and are thus suited for screening. Intensities were manually adjusted for good contrast for each strain, while the intensity range was kept identical over the time course. B) shows imaging of non-pigmented Xenorhabdus nematophila indicator strains. Strains were constructed using the CRISPR-Cas12 approach described in this patent. In these strains, BGCs rxp, ppyS, Odilorhabdin (odlC) were replaced by a mNeonGreen gene. Strains were spotted onto LB agar plates and imaged at different days using an automated Leica Thunder Imager stereo microscope. Selected indicator strains develop fluorescence over time and are thus suited for screening. Intensities were manually adjusted for good contrast for each strain, while the intensity range was kept identical over the time course. Figure 18 shows the method to obtain multi-producer strains. First strains with single BGC activation in clean background (without other active BGCs) producing single secondary metabolites are identified and analysed for the individual bioactivities of the metabolites. These experiments allow the correlation between BGC and SM with interesting bioactivities and which can be combined. Thus, the so individuated BGC are inserted together into a single strain to generate a multi-producer strain, which can be used for applications in animal health, agriculture and medicine. Figure 19shows suitable crRNA frameworks: A) A crRNA framework consisting of 5 components: 1. host specific promoter, constitutive or inducible, or derived from a housekeeping gene; 2. A leader sequence; 3. cas12 specific direct repeat; 4. A dummy sequence carrying two opposite type II restriction enzyme recognition sites separated by at least 4 basepairs for scarless insertion of target specific spacer sequence; 5. a transcription terminator. After assembly a target specific crRNA array is obtained. Since the spacer sequence is not framed by two direct repeats, it is not fully processed by the cas12 enzyme and the length of the spacer should be 20-23 bp; B) crRNA framework consisting of the same components as in A only with further direct repeat behind the dummy spacer sequence. This provides for independent processing of the pre-crRNA. Here, in addition, with simultaneous fusion with homologous regions, two distinct crRNA arrays can be created (to target leading and lagging strand). R repair templates for the double-strand break is located in between. C) Structure as in B crRNA array GAR-P04397WO09 Application (final)2.docx assembled by short DNA fragments carrying a target-specific spacer sequence and a cas12 direct repeat. Depending on the strength of the promoter, up to 10 spacers can be transcribed. D) Opposed crRNA framework. Assembly introduces target-specific spacers, direct repeats, terminators, and repair templates. Figure 20 shows A) Investigated biosynthetic gene cluster dpr (deoxy-puromycin) of X. nematophila ATCC 19061, graphical representation via antiSMASH; the red arrow marks the position of the promoter exchange. B) Base peak chromatograms (BPC) of the induced production cultures (top = Sf900 medium , bottom = XPP medium) of X. nematophila ΔhfqΔPdprA::vanR_PvanCC in the retention time range between 2 and 7 min; induced in blue, non-induced in red, wild type in green; with the mass to charge ratios (m/z) of the strongest signals; measured by RP-UPLC-ESI-qTOF-MS (Impact). C) MS/MS spectra of induced production cultures (Sf900, ¹³C, ¹⁵N medium); showing the mass shifts as well as the postulated structural and molecular formulae and molecular masses in Dalton (Da); the MS spectrum corresponds to the retention time between 4.3 - 4.6 min; measured by RP-UPLC-ESI- qTOF-MS (Impact). Figure 21 shows spectroscopic data from NMR measurements (¹H (500 MHz) and 1³C (125 MHz)); HMBC correlations as arrows, COSY correlations as bold bonds; sample in DMSO-d6, δ in ppm, J in Hz. A) Structure of demethoxypuromycin (M1, 27) (441 Da). B) Structure of N-acetyl- demethoxypuromycin (M2, 28) (483 Da). C) Structure of N-formyl- demethoxypuromycin (M3, 29) (469 Da). Figure 22 shows A) Investigated biosynthetic gene cluster xab of Xenorhabdus doucetiae, graphical representation via antiSMASH; the red arrow marks the position of the promoter exchange. B) Promoter exchange in ΔcyaA results in specific production of Xenoamicine in the “cleaner” background as comparison to Wiltype in Xenorhabdus doucetiae. HPLC/MS analysis of targeted Xenoamicine A (30) production in X. doucetiae WT and ΔcyaA are shown as base peak chromatograms (BPC) where WT, ΔcyaA, induced are represented with black line and WT and ΔcyaA non-induced with gray line. GAR-P04397WO09 Application (final)2.docx Figure 23 shows chemical structures of further rupshomycin derivatives 31 – 44 prepared according to the methods described herein. Figure 24 A)shows extracted-ion chromatograms (EIC) of rupshomycin derivatives 26, 31, and epoxy-rupshomycin derivatives 45 – 48; B) chemical structures of epoxy-rupshomycin derivatives 45 – 48; C) mass spectra of compounds 26, 31, 46 and 47. Figure 25 upper part shows extracted-ion chromatograms (EIC) of rupshomycin derivatives 49 – 52; lower part shows chemical structures of rupshomycin derivatives 49 – 52. The following examples are included to demonstrate preferred embodiments of the invention. It should be appreciated by those of skill in the art that the techniques disclosed in the examples which follow represent techniques discovered by the inventor to function well in the practice of the invention, and thus can be considered to constitute preferred modes for its practice. However, those of skill in the art should, in light of the present disclosure, appreciate that many changes can be made in the specific embodiments which are disclosed and still obtain a like or similar result without departing from the scope of the invention. Further modifications and alternative embodiments of various aspects of the invention will be apparent to those skilled in the art in view of this description. Accordingly, this description is to be construed as illustrative only and is for the purpose of teaching those skilled in the art the general manner of carrying out the invention. It is to be understood that the forms of the invention shown and described herein are to be taken as examples of embodiments. Elements and materials may be substituted for those illustrated and described herein, parts and processes may be reversed, and certain features of the invention may be utilized independently, all as would be apparent to one skilled in the art after having the benefit of this description of the invention. Changes may be made in the elements described herein without departing from the scope of the invention as described in the following claims. GAR-P04397WO09 Application (final)2.docx Examples Material and Methods Bacterial culture conditions Photorhabdus luminescence laumondii subsp. TTO1 and Xenorhabdus doucetiae were grown in LB with shaking for at least 16 hours at 30°C. E. coli strains were grown in LB with shaking for at least 16 hours at 37°C. The medium was supplemented with kanamycin (50 μg/ml), ALA (5-Aminolevulinic acid) (50 μg/ml), DAP (Diaminopimelic acid) (300µM) or 0.2% L-arabinose when appropriate. Promoter exchange mutants were induced by adding L-arabinose (0.2%, v/v) to the cultures. All plasmids and strains used in this study are listed in Table 2. Production of selected metabolites took place in XPP3 medium or Bacto™ CD Supreme Fermentation Production Medium (SFPM) for 72 h at 28 °C. Transposon Mutants Construction Transposon mutagenesis was performed by conjugating Xenorhabdus doucetiae and Photorhabdus laumondii with a pool of donor E. coli APA752 (harboring the pKMW3 (mariner transposon vector library with ~3 million unique 20mer DNA barcodes flanked by common PCR priming sites) in WM3064 (conjugation donor strain)). APA752 was a gift of Prof. Adam Deutschbauer (Berkeley, California, USA). The donor strain APA752 and the recipient strains X. doucetiae and P. laumondii were grown to mid-log-phase (OD 0.6 to 0.8) then mixed at a donor/recipient ratio of 1:3 for 24 h at 30°C on LB agar plates. The conjugation reaction mixtures were scraped into LB and the cells plated on LB agar plates supplemented with 100µg/ml Kanamycin, and incubated the plates at 30°C. After 2 days of growth, non-fluorescent colonies were selected and those were grown in 10ml LB with 100µg/ml Kanamycin at 30°C to a final OD of 1.5. Final volume of 20% glycerol was added, 2ml -80°C freezer stocks were made, and simultaneously cell pellets were collected for genomic DNA extraction for Whole genome sequencing. Genomic DNA extraction For sequencing of transposon-insertion mutants, genomic DNA was extracted using the DNeasy Blood & Tissue Kit (Qiagen) following the manufacturer’s instructions. Whole Genome Sequencing and identification of Transposon insertion sites GAR-P04397WO09 Application (final)2.docx Genomic DNA mutant libraries were constructed using NEBNext Ultra II FS DNA Library preparation Kit and Whole genome sequencing was performed using 2 x 150bp paired-end chemistry on Illumina MiniSeq platform. Transposon insertion sites were identified by mapping the IR and IL (Right and Left Inverted Repeat sequence of the mariner Transposon) against each sequenced fastaQ file of individual mutants and viewed in Geneious Prime (https://www.geneious.com). Metabolite extraction and HPLC–MS/MS analysis Fresh LB medium (10 ml) was inoculated with an overnight culture to an OD600 of 0.1. After 72 h of cultivation at 30 °C with shaking, 500 µl of the culture was mixed with equal volume of Methanol and vortexed at full speed for 1 min. The Mixture was then diluted to 1:5 with Methanol and centrifuged for 20 min at 13,000 r.p.m. and the supernatant was directly subjected for analysis by HPLC–MS/MS using a Dionex Ultimate 3000 system with a Bruker AmaZon Speed mass spectrometer. The peak areas of the compounds were quantified using DataAnalysis (Bruker). Metabolite production, extraction and HPLC–MS/MS with absorbing Amberlite XAD-16 resin For in situ extraction of metabolites 10 ml production medium containing appropriate antibiotics and 2% (v/v) of XAD-16 slurry, was inoculated to an OD600 of 0.5 and incubated at 30 °C until OD600 of ≈1 was reached. Afterwards the appropriate inducers were added and the culture was set to 28 °C. After 72 h incubation under shaking conditions (180 r.p.m.), the culture supernatant was removed while the XAD-16 resin remained in the flask. 10 ml of methanol was added to the resin and the metabolites were extracted during an incubation time of 1 h at room temperature with continuous shaking.1 ml of the extraction was then diluted to 1:5 with Methanol and centrifuged for 20 min at 13,000 r.p.m. and the supernatant was directly subjected for analysis by HPLC–MS/MS using a Dionex Ultimate 3000 system with a Bruker AmaZon Speed mass spectrometer. DataAnalysis (Bruker) was used to analyse and quantify the chromatograms and peak areas of the compounds. Flow cytometry for characterization of expression dynamics of the reporter strains. Flow cytometry measurements were performed on a BD Fortessa Flow Cytometer (BD Bioscience) to select reporter strains and optimize growth condition, e.g. time point for maximal expression of reporter genes and media with highest expression level. For this, cells were grown for 1-3 days in low-salt LB medium. Other media, such as minimal media (M9 and derivatives), insect cell culture media (Sf900 II) or GAR-P04397WO09 Application (final)2.docx defined production media (XPPM or XPP3) can also be used, depending on the expression profile of the reporter genes. The samples were washed once with PBS (pelleting at 5000 rcf for one minute) and diluted 1:300 with PBS before measuring. Reporter strains carrying for example mNeonGreen and mScarlet were measured using the 488 nm and 561 nm laser lines (100 mW) and the bandpass filter 510/20 and 586/15 respectively. Gating was set according to forward scatter, sideward scatter and fluorescence signal.30,000 events were acquired. The data were recorded using the BD FACS DIVA software (BD Bioscience). This kind of experiment is suitable for high throughput approaches (see M4). FACS for collecting of possible candidates with deletion of global regulators. Fluorescence activated cell sorting measurements were performed on a BD FACSAria^TM Fusion Flow Cytometer (BD Biosciences). Reporter strains carrying mNeonGreen and mScarlet were measured after transposon mutagenesis. Cells were excited with 488 nm and 561 nm lasers (100 mW) and fluorescence was recorded using appropriate filter sets. Gates for sorting were set to sort for cells without any fluorescent signal and double fluorescence (negative control). Screening of indicator mutants having loss fluorescence emission Identification of potential global regulator mutants can be performed by different methods at varying throughput (Table 1). Table 1: Methods for screening of fluorescent reporter strains Method Sensitivity Throughput Time effort (M1) Fluorescence imaging of colony High Low High smear (M2) Stereo microscopy of colonies on Medium Medium Medium solid agar (M3) Fluorescence spectroscopy using Medium - Medium - Medium a microplate reader High High (M4) FACS High High Low M1) Fluorescence imaging of colony smear This screening method is based on manual fluorescence microscopy imaging using an upright or inverted fluorescence microscope with a high magnification objective and a sensitive detector (preferably cooled EMCCD or sCMOS camera). For example it can be made by using a Zeiss AxioPlan 2 upright wide field microscope with a 100x oil NeoFluor phase contrast objective and a halogen lamp. GAR-P04397WO09 Application (final)2.docx Colonies are picked with a sterile tip or spatula and smeared onto a standard microscopy glass slide. The smear is covered with a 170 µm thick cover glass (optional: add a drop of buffered solution, e.g. PBS), mounted onto the microscope and imaged in phase contrast and fluorescence mode. Fluorescence signal of bacterial cells is recorded using appropriate filter sets (here: Zeiss GFP filter cube for mNeonGreen or Zeiss Texas Red filter cube for mScarlet-I). This approach has a low throughput, but equipment is available in many laboratories. M2) Stereo microscopy of colonies on solid agar For faster screening of transposon mutants, colonies on solid agar (typically grown for 2-5 days) can be imaged using a stereo microscope with a white light and fluorescence module. Systems with automated stages increase the throughput as they facilitate screening of entire plates. Here, a Leica ThunderImager M205FC with an LED illumination system can be used. Non-fluorescent colonies are identified in overlays of fluorescence and white light images and can be subsequently picked and cultured. Sequencing and HPLC-MS is used to identify global regulator mutants. M3) Fluorescence spectroscopy using a microplate reader Transposon mutants can also be screened using microplate readers. Microtiter plates (96-well or 384-well format) are inoculated with single colonies from selection agar plates. Plates are incubated at optimized conditions for 1 – 3 days and subsequently measured using a microplate reader with absorption and fluorescence modules. For this, a Tecan Spark system with a fluorescence module can be used. Measuring the OD600 for each well reports on the biomass, while the fluorescence signal in two spectral windows is recorded to screen for loss of reporter protein fluorescence. Automatic colony picking using robotic systems increase the throughput, as shown here using a Singer PIXL colony picking robot. M4) FACS FACS allows for sorting of non-fluorescent bacteria from liquid cultures at high throughput. After transposon mutagenesis, bacteria are grown in liquid medium including appropriate selection markers for 1-3 days. As FACS can separate individual cells with specific properties, culturing on solid agar is not required. Non- fluorescent cells can be sorted either directly into well plates or into reaction tubes followed by streaking onto solid agar to isolate individual mutant clones. Sorting into well plates can be combined with M3 to verify the loss of fluorescence. In the examples described herein was used a BD FACSAria^TM Fusion Flow Cytometer. GAR-P04397WO09 Application (final)2.docx Strains, plasmids, and growth conditions for BGC/ fluorescence reporter replacement and BGC activation/refactoring All bacterial strains and plasmids used are listed in Table 1. E. coli DH10B were used as cloning for plasmid construction E. coli ST18 was used as donor strain for conjugation to transfer plasmids into Photorhabdus laumondii subsp. laumondii TTO1 and Xenorhabdus nematophila ATCC 19061. E. coli was cultured in LB medium at 37 °C, and Photorhabdus/Xenorhabdus was cultured in LB medium at 30 °C. All liquid cultures were incubated at 200 rpm and antibiotics and other supplements were added as follows: 50 µg/ml kanamycin (Km) and 50 µg/ml ALA for E. coli. 25 µg/ml kanamycin for Photorhabdus/Xenorhabdus.1.5 g/L agar was added to LB for solid plates. In addition, the concentration of L-arabinose (Ara) and anhydrotetracycline (AHT) to induce expression of the Cpf1 protein and lambda red proteins was 0.4 % (w/v) and 200 nM, respectively. All strains were kept as glycerol stocks prepared in LB containing 25% glycerol at −80 °C. Plasmid Construction for BGC/ fluorescence reporter replacement based on pAR20 series The empty pAR20 was constructed in silico and synthesized as whole plasmid by Double Helix Technologies (DOULIX™). To overcome multiple assembly rounds, the repair template containing homologues regions left and right (HR-L, HR-R) was fused together with target specific crRNA sequence on a synthetic dsDNA fragment (Figure 1B). The position of the left/ upstream homologues region was selected appropriately to conserve the native regulation of the gene and generate a fusion protein from partial origin gene and the fluorescent reporter. For this purpose, 350 bp of the UTR and and 150 bp of the coding gene, including the start codon, were selected. The right homologues region was selected depending on the desired deletion size. The sequence does not necessarily have to be deleted as long as the PAM sequences of the selected spacers are mutated and another double strand break is prevented. The selection of the target spacer (TS), wherein TS-B is located shortly before HR-R, and TS-A is located shortly after the HR-L, was made by using the “CRISPR Sites” prediction function of the cloning software Geneious Prime. The selection criteria were target spacer with 31 bp length (23 bp minimum length) and TTTY as PAM sequence. At least one spacer sequence is selected per editing procedure. Selecting two spacer sequences, targeting each leading and lagging strand, the best results are achieved. Target spacer, homology repair templates and fluorescent reporter gene were ordered as synthetic dsDNA gene fragments, from Twist Bioscience and Integrated DNA GAR-P04397WO09 Application (final)2.docx Technologies, respectively (Figure 1B). The NEB Golden Gate assembly mix containing pAR20 and dsDNA inserts was prepared according to the manufacturer's instructions resulting in a final editing plasmid (Figure 1B). After the reaction, 1-2 µl of the mix was transformed into chemically or electro competent E. coli cells. Correct assembly was checked by colony PCR using primer pair AR533/534. Regulatory seuqences and homology repair templates are listed in Table 7c. Selected target spacer can be found in Table 7b. Plasmid Construction for BGC activation/refactoring based on pAR20 series For all cluster activations and refactoring, the above described pAR20-empty was used. The TS sequence was selected as follows: A region 50 - 1000 bp upstream of the cluster of interest were screened and annotated using the “CRISPR Sites” prediction (Figure 1C). Two sequences were selected, oriented in opposite directions to target the leading and lagging strand respectively. The average GC content was between 30-60%, sequences with more than two Ts in a row were excluded. The left homologous region were then identified upstream of the most left selected target spacers with a minimal distance of 50 bp to the PAM sequence. The length was 500 (+/-100) bp and the average GC content was between 30 and 60% (Figure 1C). The right homologues region is located downstream of the most right target spacer, but it must initiate with the start codon of the gene to be activated (Figure 1C). In cases where the described distances could not be maintained, e.g. due to a limited number of suitable target spacer sequences, target spacer sequences located in the later homologous regions were also selected. Here artificial silent mutations were introduced into the PAM sequence to prevent the CRISPR complex from 'attacking' the repair template. Target spacer, homology repair templates and regulatory sequence (inducible promoter and regulator) ordered as synthetic dsDNA gene fragments, were obtained from Twist Bioscience and Integrated DNA Technologies, respectively (Figure 1C). The assembly is carried out with the NEB Golden Gate assembly mix containing pAR20 and dsDNA inserts was prepared according to the manufacturer's instructions resulting in a final editing plasmid (Figure 1C). After the reaction, 1-2 µl of the mix was transformed into chemically or electro competent E. coli cells. Correct assembly was checked by colony PCR using primer pair AR533/534. Regulatory seuqences and homology repair templates are listed in Table 7c. Selected target spacer can be found in Table 7b. Plasmid Construction for BGC or single gene deletion based on pAR20 series GAR-P04397WO09 Application (final)2.docx For all cluster activations and refactoring, the above described pAR20-empty was used. The TS sequence was selected as follows: within the coding sequence of the BGC/gene of interest were screened and annotated using the “CRISPR Sites” prediction (Figure 2C). Two sequences were selected, oriented in opposite directions to target the leading and lagging strand respectively (Figure 2C). The average GC content was between 30-60%, sequences with more than two “T”s in a row were excluded. The left homologous region were then identified upstream of the most left selected target spacers with a minimal distance of 50 bp to the PAM sequence, the region can be located within the coding sequence for a partial deletion or before the start codon for a complete deletion. The length was 500bp (+/-50bp) and the average GC content was between 30 and 60% (complete deletion, Figure 2C). The right homologues region is located downstream of the most right target spacer, the region can be located within the coding sequence for a partial deletion or behind the stopp codon for a complete deletion (complete deletion, Figure 2C). In cases where the described distances could not be maintained, e.g. due to a limited number of suitable target spacer sequences, target spacer sequences located in the later homologous regions were also selected. Here artificial silent mutations were introduced into the PAM sequence to prevent the CRISPR complex from 'attacking' the repair template. Target spacer, homology repair ordered as synthetic dsDNA gene fragments, were obtained from Twist Bioscience and Integrated DNA Technologies, respectively (Figure 2C). The assembly is carried out with the NEB Golden Gate assembly mix containing pAR20 and dsDNA inserts was prepared according to the manufacturer's instructions resulting in a final editing plasmid. After the reaction, 1-2 µl of the mix was transformed into chemically or electro competent E. coli cells. Correct assembly was checked by colony PCR using primer pair AR533/534. Regulatory sequences and homology repair templates are listed in Table 7c. Selected target spacer can be found in Table 7b. Electro transformation and biparental conjugation pAR20 plasmids could be introduced into the target bacterial strains either by electro transformation (BTX™ ECM™ 630 Exponential Decay Wave Electroporator) or by conjugation. Electro competent Photorhabdus and Xenorhabdus cells were prepared following standard protocols. For conjugation of the pAR20 derivatives overnight cultures of E. coli ST18, having a hemA deletion mutation, and Photorhabdus/Xenorhabdus were used, respectively. The optical density of the two cultures was measured and set to a GAR-P04397WO09 Application (final)2.docx ratio of 4:1 Recipient/Donor in a total volume of 1 ml. The cell mixture was centrifuged at 5000 x g and washed twice with 1 ml LB. Finally, the cell pellet was resuspended in 100 µl LB and spotted onto a LB agar plate containing 50 µg/ml 5- aminolevulinic acid, ALA. The next day, the cell mass was scraped off and resuspended in 1 ml LB. A dilution of 1:50 was plated on a selection plate with 25 µg/ml kanamycin (Km) and without ALA in order to select only for Photorhabdus/Xenorhabdus mutants and counterselecting for E. coli, due to the hemA deletion causing a defect in tetrapyrrole biosynthesis. Cpf1 (Cas12a) assisted gene editing (BGC activation, BGC/FR replacement, BGC deletion) with pAR20 series and plasmid curing For general gene editing, a strain carrying a gene-specific pAR20 vector was inoculated as a 5 ml overnight culture in a 50 ml Erlenmeyer flask. The next day, this culture was diluted to a final OD of 0.5 in 10 ml LB containing 25 µg/ml kanamycin. The culture was then incubated at 30 °C until an OD of 0.8 - 1.0 was reached. After addition of AHT, the culture was further incubated at 25 °C for 1h. Subsequently, L-arabinose was added and incubated for another 3 h at the same temperature. Finally, 50 µl of the cell suspension was plated on a selection plate with kanamycin and arabinose. Successful editing approaches were confirmed by colony PCR. To generate a plasmid free stain a 1:500 dilution of the overnight culture was inoculated into fresh LB culture containing 6% sucrose and incubated for futher 20 h. This culture could be used directly for further rounds of genome editing. Example 1: Transposon mutagenesis and mutant screening based on loss- of-fluorescence Many bacterial strains potentially producing interesting secondary metabolites form non-pigmented colonies, rendering visual identification by color unsuitable. Replacing sequences of BGCs, such as NPRS, in such non-pigmented strains by fluorescent reporters, i.e. fluorescent proteins, allows for identification of global regulator mutants using fluorescence microscopy, spectroscopy or fluorescence- assisted cell sorting (FACS) . For the loss-of-fluorescence based screening, genetic replacement was performed in frame after the first 9 – 150 amino acids of the target enzyme of Xenorhabdus nematophila to avoid disturbance of native gene regulation, as regulatory elements are often positioned within the coding region. Notably, these mutants can be constructed using classical methods, e.g. suicide plasmids, or the CRISPR/Cas- GAR-P04397WO09 Application (final)2.docx based method presented here to increase the throughput. To screen for global regulator mutants the inventors created indicator strains in which highly expressed NRPS encoding genes are replaced by fluorescent reporters, so that the fluorescent reporter is under control of the same regulatory elements as the original NPRS encoding gene. Suitable indicator strains can also be created by replacing another gene being part of the BGC instead of NPRS. BGCs responsible for Rhabdopeptide production was chosen as model BGC due to their high expression level. Growth conditions were optimized in 96-well format using a microplate reader Tecan Spark, to ensure that reporters were expressed at detectable levels. Figure 17A shows Photorhabdus luminescens TTO1 indicator strains where BGCs stlCDE (Isopropylstilbene), ppyS (pyrones), and AQMT4 (anthraquinone) were replaced by a mNeonGreen gene. Figure 17B shows Xenorhabdus nematophila indicator strains, where BGCs rxpA-C (XNC1_2228 – 2230) (Rhabdopeptides (9-12)), ppyS, and odlC (Odilorhabdins) were replaced by a mNeonGreen gene. Afterwards, the constructed indicator strains were subjected to transposon mutagenesis (Method section). Following transposon mutagenesis, cultures were plated out on LB agar plates including appropriate selection markers, incubated at suitable conditions (see Methods) and colonies were screened for the absence of fluorescence signal as described in the Method section above. Absence of fluorescence signal of one reporter might be the result of transposon integration into the fluorescent reporter itself or the promoter region of the respective NRPS. Absence of both reporter signals, however, might indicate transposon integration into the genomic locus of a global regulator. Candidate mutant bacteria colonies having lost fluorescence emission were verified by sequencing and HPLC-MS in order to identify global regulator gene: If no production of secondary metabolites is found in the mutants by HPLC/MS analysis, suggesting that the transposon might have hit the global regulators involved in the global regulatory pathways, WGS was performed in those mutants GAR-P04397WO09 Application (final)2.docx in order to identify the transposon insertion sites and thus the global regulator gene affecting the global regulation of secondary metabolite biosynthesis. More than two fluorescent reporters could be used, but this might affect the strain fitness and additionally increases the complexity of the screening procedure. Only non-essential global regulators can be identified with this method, as mutants have to be isolated and cultured for strain verification and characterization. Example 2: Optimization of the two-plasmid-based CRISPR/Cpf1 method for Photorhabdus The present method represents an improvement of the CRISPR/Cpf1 editing method described by Ao X et al. 2018 (Front. Microbiol. 9:2307). A helper and a donor plasmid were used to perform genome editing supported by the lambda recombination system. The helper plasmid p46Cpf1-OP2 encodes an E. coli codon-optimized variant of the cpf1 gene under the PBAD promoter, which is inducible with L-arabinose (Ara), and the lambda red (gam, exo, bet) recombination system controlled by a Ptet promoter, inducible with AHT. The donor plasmid is based on a high copy pUC vector carrying the crRNA sequence for a specific target gene, as well as homology regions to the target serving as repair templates after double strand break. Cas12a processes the transcript from the donor plasmid to generate mature crRNAs. Guided by the crRNA, Cas12a finds the genomic target and induces a double-strand break. Recombination occurs between the genomic target and the donor DNA mediated by l-Red. In order to validate this method in Photorhabdus laumondii TTO1, the stlA gene was selected as the first target for genome editing because of an easily recognizable phenotype (Figure 2A). StlA is a phenylalanine ammonia lyase involved in the biosynthesis of isopropylstilbene (IPS; 1) produced by all Photorhabdus strains (Figure 2B) and its deletion results in overproduction of the orange anthraquinone pigment. The stilbene biosynthetic gene “cluster” in P. luminescens comprises a stilbene epoxidase gene (plu2236), which is adjacent to stlA (plu2234), a phenylalanine ammonia lyase that converts phenylalanine to cinnamic acid, initiating phenylpropanoid/stilbene biosynthesis. A donor plasmid (pAR18, Figure 2C) was designed based on the pTargetF (Addgene # 62226) vector for constitutive expression of crRNA (specific for a target DNA), with gentamycin resistance as well as the sacB gene as counter-selection marker enabling rapid loss of the donor plasmid allowing for several rounds of GAR-P04397WO09 Application (final)2.docx genome editing. Moreover, the donor plasmid comprises homology regions left and right (HR-L and HR-R) to the target serving as repair templates after double strand break. Two crRNA sequences were used for each deletion to enable targeting of the leading and lagging strand, respectively. For this purpose was constructed a synthetic framework consisting of the constitutive promoter J23119, a transcriptional terminator and the direct repeats of the crRNA sequence. The inventors modified a standard CRISPR array replacing the spacer sequence between the direct repeats by two BsaI restriction sites containing spacer sequence, (also named spacer dummy, SD) (Figure 2C, 2D). The stlA specific target spacers were determined by "Annotate & Predict" function of Geneious Prime, "TTTN" was set as PAM site and a target spacer length of 23-31 bp. Furthermore, to facilitate plasmid assembly, the homology repair arms (HA-L/HA- R; ~500 bp) were each coupled with one of the crRNAs and synthesized as a dsDNA fragment (Figure 2C). Since the original p46Cpf1-OP2 of Ao et al., 2018 was not transformable into Photorhabdus, the inventors first exchanged the origin of replication from pSC101 to p15A resulting in helper plasmid pAR16, assuming it would increase transformation efficiency. The stlA-specific donor pAR18, assembled by the Golden Gate reaction, was transformed, together with helper pAR16 into Photorhabdus laumondii TTO1 by electroporation (Figure 2D). To determine the optimal starting OD600 of the liquid CRISPR culture, OD = 0.1, 0.2 and 0.5 after inoculation from an overnight culture were selected. Since Photorhabdus has a much slower doubling time compared to E. coli, the required OD600 of 0.8-1.0 could not be achieved within a single working day when the starting OD600 was below 0.5. Therefore, 0.5 was chosen as the starting OD600 of the liquid culture for the following experiments. When the OD600 of 0.8-1.0 was reached, the inducers for cpf1 (Ara) and lambda red (AHT) were added. As the system was previously tested (Ao et al., 2018) only the overall method instead of the individual components of the system, was checked. To reduce cell growth and promote protein expression, the inventors tested if temperature had an effect on the editing after induction of all components. Briefly, constant incubation at 30°C was compared with a culture that was incubated at 25°C after induction. An editing efficiency of 100% in the low-temperature culture was observed whereas only half of the tested colonies previously grown at 30 °C were positive. GAR-P04397WO09 Application (final)2.docx Example 3: Construction of the single-plasmid CRISPR-Cpf1 approach Since it was observed Photorhabdus had poor transformation efficiency and Xenorhabdus was not transformable at all with the p46Cpf1-OP2 and its derivative pAR16, the inventors decided to develop a single plasmid solution. Based on the broad-host vector pSEVA231(GenBank: JX560328.1), a plasmid pAR20 combining the components from the donor plasmid pAR18 and helper plasmid p46Cpf1-OP2 was constructed. A major advantage of the method is the possibility to conjugate the plasmid directly from E. coli to the recipient strain without any integration of the plasmid or its parts into the genome. To test its efficiency, stlA (plu2234) gene was deleted. The results showed that stlA was deleted in all colonies (Efficiency = 100%) that had the expected pigmentation phenotype (Figure 2A, Figure 4, Table 3). The BsaI digested pAR20 (Figure 3) can be used for CRISPR/Cpf1 mediated genome editing such as deletions, promoter exchange and replacement of sequences with fluorescent reporters. In addition to the deletion of small gene sequences such as stlA (plu2234, 1.9 kb deletion), the inventors wanted to evaluate the potential of the method for medium and large deletions and whether the editing process can be speed up. The inventors focused on genes whose manipulation has visible phenotypes or results in metabolite changes easily detectable by mass spectrometry. The selected and successfully deleted genes/genome segments include (Table 3, Figure 4): gxpS (plu3263, 15.4 kb deletion) in TT01 and xcnA (XNC1_1711, 7.5 kb deletion) in Xenorhabdus nematophila, rxpABC (XNC1_2228 – 2230, 15.7 kb deletion) in Xenorhabdus nematophila Efficiency was determined by dividing the number of positive edited colonies by the total number of colonies tested. The corresponding agarose gel electrophoresis pictures are shown in Figure 5. Target spacers used for each approach are listed in Table 7b. Large gene deletions up to 15 kb in P. laumondii TTO1 and X. nematophila were easily accessed with high efficiency (Table 3). Furthermore, there was no major impact on the metabolic profile after deletion of gxpS in P. laumondii TTO1 or xcnA in X. nematophila except the expected loss of GameXPeptides and xenocoumacins, respectively. Deletion of the rxpABC genes responsible for the production of rhabdopeptide (9-12) in X. nematophila however also leads to an additional loss of xenortide A (6) as well as an increase of xenocoumacin II (8) GAR-P04397WO09 Application (final)2.docx (Figure 8D, third line). These findings indicate a regulatory or metabolic network of natural products in X. nematophila associated with rhabdopeptide biosynthesis that will be studied in the future. Example 4: Induction of secondary metabolites by insertion of regulatory sequences in target BGC. In addition to deletions, the use of small regulatory sequences like inducible promoters is particularly important in natural product research and for biosynthesis elucidation. For this purpose, various inducible promoters described in Table 1 (Nat Chem Biol, 2019.15(2): p.196-204) were tested, in particular those featuring an insulator (riboJ) and a strong ribosomal binding site (RBS) to switch on and off different genes and gene clusters. As shown in Figures 10 and 12, activation of Safranin biosynthetic gene cluster and of rupshomycin biosynthetic gene cluster requires also the presence of such additional regulatory elements. As example, indC was selected, which encodes a NRPS involved in the biosynthesis of the blue pigment indigoidine. This gene is silent under laboratory conditions but can be activated by the introduction of a foreign promoter. For the CRISPR/Cpf1 approach, the homology regions “selected” are positioned 500 bp upstream of the indC coding sequence (HR-L) and 500 bp downstream of the start codon (HR-R), while the distance between both can be variable (Figure 6A). In contrast to a deletion, a sequence of the VA inducible promoter system (SEQ ID NO 131) was assembled between the homology arms during golden gate assembly (Figure 6B-C). After the editing approach, the sequence between the homology regions was replaced by the promoter sequence comprising the repressor vanC in reverse direction with the related elements: PJ23100, RBS, insulator and a terminator, and the inducible PvanCC with an insulator and RBS element "in frame" with indC. The colonies were tested by PCR and showed 100% editing (Figure 5). After induction of the promoter with vanillic acid, the typical blue pigment was observed (Figure 6D). This approach was also applied to other genes of known BGCs facilitating overexpression of previously moderate produced metabolites as well as production of previously “silent” BGCs. The successfully edited targets are listed in Table 3 and include the different compound classes: Glidobactins (4-5) (glbA), GameXPeptide A (3) (gxpS), Isopropylstilbene (1) (stlA), Rhabdopeptides (9-12) (rxpA), and Xenocoumacin I & II (7-8) (xcnA). MS spectra of induced and non- induced cultures after promoter insertion are shown in Figure 7. In general, a GAR-P04397WO09 Application (final)2.docx significantly higher production of natural products was observed through compared to the wild type level. As previously observed during rxpABC deletion, the promoter exchange upstream of rxpA had an impact on xenortide A (6) production. While 6 was still detectable in the non-induced culture, it was significantly reduced after induction of the rxp BGC, which might be due to the cross talk between RxpABC and XrdAB as described above. Example 5: Activation and refactoring of the silent BGC mxn (madumycin II) Like indC or glbA the putative pristinamycin II BGC (Figure 8A) is not active under laboratory conditions. Previous findings showed activation of the BGC during infection of Galleria mellonella larvae and a mass of 526.2 m/z [M+H]⁺ was detected, which is consistent with pristinamycin II. Feeding experiments with isotopically labeled amino acids in infected insects and highly similar BGC architecture further confirmed this. In order to activate this BGC with the above described pAR20 based approach, the region for promoter insertions were selected upstream of the gene encoding a beta-ketoacyl-ACP synthase (Table 4). For this the inventors used the VA inducible promoter system (SEQ ID NO 131) assembled with HA-L and HA-R mxnB_L/R: SEQ ID NO 159-160 on pAR20 backbone. The inventors revealed the previously identified mass of 526.2 m/z [M+H]⁺ as the sodium adduct of the mass of 504.2 m/z [M+H]⁺. HR-MS studies allowed the prediction of a sum formula (C26H37N3O7, Δppm = -0.99) consistent with madumycin II, which also belongs to the streprogramin class A as pristinamycin II. Feeding experiments with deuterated valine and alanine confirmed their incorporation and MS/MS analyses of the fragmentation pattern, what was compared with a chemical standard, confirmed that the compounds indeed is madumycin II (Figure 9 B and C). Therefore the inventors updated the nomenclature of the BGC from pxn to mxn and adapted the biosynthetic pathway according to the new findings (Figure 8A). Since the retention times of madumycin II (16) and xenortide A (6) are almost identical, strain engineering was necessary. From the previous observations, it was known that deletion of the rxp cluster also leads to loss of both rhabdopeptides and xenortides. Therefore, it was used the same construct as described above for the rxp deletion (Figure 8D) to prevent production of both compound classes. Since xenocoumacin is also becoming more dominant after rxp deletion xcnA was deleted as well, resulting in a strain with a much cleaner production of madumycin II (16). The introduction of another strong constitutive promoter (Ptac without the lacI repressor, SEQ ID NO 134) upstream of mxnL led to a substantial increase in the production titer of approximately 250 mg (Figure 8 B, C and D). The according editing plasmid was GAR-P04397WO09 Application (final)2.docx based on pAR20 with mxnK specific HA-L and HA-R (SEQ ID NOs 161-162). Production of madumycin II was performed in XPP3 medium with 2% (v/v) XAD-16 for in situ extraction. Example 6: Activation and refactoring of the silent BGC xsc (safracin) In addition to "simple" and multiple promoter exchanges, complex BGC activations are also possible with the method developed herein. The activation of the putative safracin-associated BGC, named xsc, in Xenorhabdus sp. TS4 is such an example due to its bidirectional architecture (Figure 10A and 10B I). Safracins have been previously described and characterized in Pseudomonas fluorescens. Like the mxn BGC above, this xsc (Xenorhabdus safracin cluster) BGC is not active under laboratory conditions (Figure 10B I). For activation, a strong inducible PvanCC promoter was introduced upstream of xscA and a strong constitutive promoter (proD) in the opposite direction upstream of xscI (Figure 10B II) in Xenorhabdus sp. TS4. In addition, the 5'-UTR between the RiboJ and the start codon was replaced with a translation enhancer sequence (g10T7 UTR (also abbreviated as T7g10), BBa_K1758100, sequence available online) comprising a 5' untranslated region (5'-UTR) and a strong ribosomal binding site from bacteriophage T7 gene 10 (g10-L). (Figure 10B II box). The approach is based on pAR20 editing plasmid with synthetic dsDNA fragments used for CRISPR/Cas12 mediated genome editing: xscA/xscI_ specific HA-L and HA-R (SEQ ID NOs 167-168) and SEQ ID NO 132 as promoter. To obtain SAC-B as the exclusive main product, xscH was deleted with simultaneous promoter exchange before xscK (Fig 10 B III). Herefore the following synthetic dsDNA fragments used for CRISPR/Cas12 mediated genome editing for pAR20 based assembly were used: xscKΔxscH specific HA-L and HA-R (SEQ ID NOs 169-170) and SEQ ID NO 136 as promoter sequence. High SAC-B production is very valuable as SAC-B can be used as starting material for semisynthetic approaches to produce potent antitumor drugs (ET-743 and (-)-jorumycin, Figure 11A). With the strain III production titers for SAC-B 150 mg/ml can be reached, which is higher than production reached in the prior art CN103074395B, and CA2510069A1. Production of SAC-B was performed in XPP3 medium with 2% (v/v) XAD-16 for in situ extraction. The production of SAC- B by the constructed Xenorhadus sp. TS4 SAC-B producer strain (shown in Fig 10 B III) was compared to E. coli strain LZ84 harboring the xsc Cluster encoded on three expression plasmids (pCola_PBad_ xscA-H, pACYC_PBad_xscIJ, pCDF_PBad_xscK, Table 2). Triplicates were made from both strains and cultivated in XPP3 production medium according to the previously described “Metabolite production, extraction and HPLC–MS/MS with absorbing Amberlite GAR-P04397WO09 Application (final)2.docx XAD-16 resin” method. TS4 strains were cultivated at 28 °C and LZ84 strains at 22 °C. After cultivation, the resins were harvested, eluted with methanol and extracts were analyzed for their SAC-B production via LC-MS. With respect to the final OD600, the SAC-B amount of the constructed TS4 strain was 14 times higher than that of LZ84 (Figure 11B). Example 7: Activation and refactoring of the silent novel rpm BGC (rupshomycin) A further example of complex and cryptic cluster activation is a trans-AT NRPS/PKS hybrid cluster (rpm BGC, genes rpmA-rpmO) from Xenorhabdus indica (Figure 12 I). When testing different insertion points for single promoter exchange based on the developed pAR20 approach, new products were not detectable (Figure 12 II and III). First, an inducible promoter (Pvan modified, SEQ ID NO 131, SEQ ID NO 171- 172) was inserted upstream of rpmA (Figure 12 II), not resulting in production of a new compound. Thereafter, a promoter exchange with Pvan modified (SEQ ID NO 132, NO 173-174) was performed before rpmD (Figure 12 III), also without success. As it was presumed the presence of another regulatory sequence between rpmC and rpmD, this sequence was replaced by ribozyme RiboJ51 and the T7g10 translational enhancer in the PvanCC_rpmA strain, generating mutant strain "IV" (Figure 12 IV). For this purpose, the synthetic dsDNA fragments rpmD specific HA-L and R with SEQ ID NOs 173-174 and Translational Enhancer SEQ ID NO 135 inserted between them were used. This leads to a new compound 19 with a mass of 320 Da. Compound 19 was then isolated and structurally confirmed by NMR. However, Compound 19 is an artificially created product, as the BGC uses the inducer for the PvanCC promoter, vanillic acid, as a building block for the biosynthesis. To obtain the true natural product, the PvanCC was replaced by the IPTG inducible Ptac promoter (SEQ ID NO 136) and the gene encoding the global regulator Hfq was deleted in this strain (Figure 12 V). Both based on pAR20 gene editing with the synthetic dsDNA fragments rpmA specific HA-L and R SEQ ID NOs 171-172 for Ptac introduction and SEQ ID NOs 179-180 for hfq gene deletion. Again, a natural product could not be detected. Therefore different benzoic acid (BA) derivatives were added to the culture medium at 1mM. Results showed that all BA derivatives were accepted and incorporated by the BGC in the produced SMs (Figure 12 V). Single and double hydroxylated BAs were found to GAR-P04397WO09 Application (final)2.docx undergo further hydroxylation, putatively catalyzed by rpmG. This assumption was confirmed by deleting rpmG. In order to find the component acting as starter BA, the genes rmpA and rpmJ, encoding enzymes for starter unit biosynthesis, were overexpressed together on plasmid pAR29bad in the ΔrpmG mutant. Thereby, it could be detected compound 25, which incorporated 3-amino-4-hydroxy BA (3,4- AHBA) as a starter unit. By supplementary feeding of 3,4-AHBA this observation was confirmed (Figure 12 VIa). Subsequently, strain I (Figure 12) was fed with 3,4-AHBA in excess for three days leading to the detection of the primary product, compound 26, of the rpm BGC. The product found was named by the inventors rupshomycin (26). The inventor were also able to predict the putative biosynthesis (Fig 13). Compound 26 was obtained also after overexpression of rpmAJ encoded on pAR29bad together with rpmG encoded on pAR30bad (Figure 12 VIb). According primers are listed in Table 7a. To elucidate the influence of rpmM-O on biosynthesis, they were deleted together bases on pAR20 with the synthetic dsDNA fragments used for CRISPR/Cas12 mediated genome editing specific HA-L and R SEQ ID NOs 177-178 The resulting mutant ΔrpmM-O was then analysed for production and growth.Also with the addition of 3,4-AHBA, no growth and thus no production could be observed (Figure 12 VII). In order to analyze the growth curve, the strains were cultured in microtiter plates in a Tecan Spark microplate reader (Figure 14). A comparison was initially made between strain V and strain VII with and without the addition of 3,4-AHBA (Figure 14 A and B). Furthermore, to investigate the sole effect of 3,4-AHBA on the cells, 3,4-AHBA was added to the cells in presence or not of the rpm BGC inducer IPTG (Figure 14 A and B). In strain V, no particular growth differences were observed under the above mentioned conditions. In contrast, the ΔrpmM-O mutant showed a saddle point after 6-7 hours in growth in an induction background without the addition of 3,4-AHBA. When 3,4-AHBA was added to induced cells, a weak growth was observed in the first 3 hours, which then quickly collapsed and fell below the optical density of the starting point of the experiment. Subsequently, in order to investigate the effect of the amino group on the benzoic acid, 3,4-DHBA was fed to both strains (Figure 14 C and D). The addition of 3,4-DHBA did not lead to the complete death of the ΔrpmM-O culture, but to a growth deficiency compared to the non-induced culture (Fig 14 D). It can therefore be concluded that the amino group is crucial for the bioactivity of rupshomycin. Which of the rpmM-O genes are responsible for resistance to the biosynthesis product of the rpm BGC was the question addressed in the following studies. To GAR-P04397WO09 Application (final)2.docx this aim, rpmMN and rpmO were cloned, individually into pAR30bad expression vectors (Primer sequenced can be found in Table 7a), followed by their conjugation into the ΔrpmM-O mutant, and analysis of the growth of the resulting strains "VIII" and "IX" in presence of 3,4-AHBA and/or IPTG, to induce rpm BGC (Figure 12 VIII and IX, Figure 14 C and D). The influence of the vector was excluded by conjugating an empty vector into the strains as a control. It was observed that the genes rpmM and rpmN expressed on a vector allowed significant growth of the culture compared to the empty vector control (Figure 14 E) that resulted in a severe growth defect of the culture similar to that in Figure 14 B. For rmpO expressed on a vector, no significant growth of the culture was observed compared to the empty vector control (Figure 14 F). Therefore, it could be concluded that rpmMN together or separately are mainly responsible for the resistance to the biosynthetic products of rpm BGC. However, it might be possible that all three genes together rpmM-O are required for full resistance. Production of rupshomycins were performed in XPP3 medium with 2% (v/v) XAD-16 for in situ extraction. This approach was applied to further benzoic acid derivatives, thereby the rupshomycin derivatives 31 to 44 were obtained. The structures of compounds 31 to 44 are shown in Figure 23. By insertion of additional gene encoding styrene monooxygenase enzyme (StyA, SEQ ID NO 212) epoxy functionalized rupshomycin derivatives 45 to 48 were obtained (see Figure 24). By insertion of additional clxD gene encoding an enzyme catalyzing benzoxazole cyclisation (ClxD, SEQ ID NO 211) benzoxazole-containing rupshomycin derivatives 49 and 51 were obtained from compounds 50 and 52, respectively (see Figure 25). Extraction and Isolation of these compounds were carried out as follows exemplarily described for compounds 32 and 33: XAD beads were extracted with twice with MeOH+ 1% formic acid, and dried under reduced pressure to give a crude extract of 1.23g. The crude extract was purified by semi-preparative HPLC (20mL/min, A: water + 0.1% formic acid, B: acetonitrile + 0.1% formic acid, gradient: 5% of B for 2 min, 5% to 40 % of B in 25 min). The fraction F2 (2.8 mg) was obtained, containing an E/Z-isomer mixture of 32 in ratio of 1:1. The fraction F1 (10.8 mg) was further purified with analytical GAR-P04397WO09 Application (final)2.docx HPLC (3 mL/min, A: water + 0.1% formic acid, B: acetonitrile + 0.1% formic acid, gradient: 25% of B for 2 min then 25% to 55% of B in 12 min) leading to the isolation of fraction F1F1 (0.6 mg) containing an E/Z-isomer mixture of 33 in ratio of 1:1. 32: white amorphous solid, ESI-MS m/z: 274.0894 [M+H]⁺ corresponding to C15H16NO2S. 33: white amorphous solid, ESI-MS m/z: 289.1007 [M+H]⁺ corresponding to C15H17N2O2S.

Table 12 NMR data of compound 32 (Z)-32 (E)-32 δC δH (J in Hz) COSY HMBC (¹H to δC δH (J in Hz) COSY HMBC (¹H 1³C) to ¹³C) 118.7 a.5.29 dd (1.2, 1b, 2 2, 3 118.7 a. 5.29 dd (1.3, 1b, 2 2, 3 16.5) 16.5) b.5.16 dd (1.2, 1a, 2 3 b.5.16 dd(1.0, 9.1) 1a, 2 3 9.0) 136.3 6.38 td (10.3, 1a, 1b 3 136.3 6.38 td (10.5, 4.2) 1a, 1b 3 4,1) 132.6 6.28 m 4 1, 5 132.6 6.28 m 4 1, 5 132.0 5.85 dd (6.8, 3, 5 2 133.0 5.82 dd (6.9, 15.5) 3, 5 2, 5 15.3 ) 62.9 4.80 q (7.0) 6a, 6b 4, 6, 7 60.1 4.46 q (7.0) 6a, 6b 4, 6, 7 33.6 3.50 m 6b, 5 4, 5 34.8 a.3.26 m 6b, 5 4, 5, 7 3.10 dd (6.1, 6a, 5 4, 5, 7 b. 2.86 dd (6.9, 6a, 5 4, 5, 7 11.0) 11.0) 168.0 - 168.3 - GAR-P04397WO09 Application (final)2.docx 86.2 5.98 s 7, 9 87.5 6.31 s 7, 9 184.0 - 183.6 - 131.2 - 131.2 - 129.4 7.74 d (8.7) 12 9, 13, 15 129.0 7.64 d (8.7) 12 9, 13, 15 115.1 6.80 m 11 10, 13, 14 115.1 6.80 m 11 10, 13, 14 160.0 - 160.0 - 115.1 6.80 m 15 12, 13 115.1 6.80 m 15 128.9 7.74 d (8.7) 14 9, 11, 13 128.9 7.64 d (8.7) 14 11 - - - - - 8.45 s 5, 6, 7 Table 13 NMR data of compound 33 (Z)-33 (E)-33 δC δH (J in COSY HMBC δC δH (J in Hz) COSY HMBC Hz) (1H to (1H to 13C) 13C) 119.0 a. 5.27 dd 2 119.0 a. 5.25 dd(1.8, 2 (1.8, 16.3) 16.8) b. 5.15 dd 2 b. 5.14 dd (1.9, 2 (1.9, 10.2) 10.2) 136.3 6.39 m 1a, 1b 136.3 6.39 m 1a, 1b 132.9 6.29 dd 4 132.9 6.26 dd (2.9, 9.8) 4 (2.9, 10.8) 132.6 5.83 dd 5 133.0 5.80 dd (7.2, 3, 5 2 (6.8, 15.0) 15.1) 63.1 4.77 dt 6a, 6b 4 60.2 4.44 dt (7.0, 7.1) 6a, 6b 4 (7.0, 6.7) 132.2 a.3.49 dd 5, 6b 132.2 a.3.23 dd (7.4, 5, 6b (7.3, 11.0) 11.1) b. 3.09 dd 5, 6a b. 2.83 dd (6.9, 5, 6a GAR-P04397WO09 Application (final)2.docx (6.1, 11.0) 11.1) nd - 167.2 - 86.2 5.86 s 9 87.8 6.25 s 9, 7 185.5 - 184.5 - 136.4 - 131.6 - 117.1 6.99 dd 12 13 116.7 6.90 dd (8.3, 2.1) 12 15, 13 (8.2, 2.2) 114.1 6.64 d 11 10 114.1 6.65 d (8.1) 11 10 (8.0) 147.4 - 146.7 - Nd - Nd - 113.7 7.17 d 11, 13 11 113.5 7.08 d (2.1) 11 11, 13 (2.3) Table 14 HR masses [M+H]+ of compounds 26, and 31 – 52. Cpd. No. formula found expected deviation 31 C15H15NO3S 290.084 290.084 0.000 26 C₁₅H₁₆N₂O₃S 305.095 305.095 0.000 32 C15H14NO2S 274.090 274.090 0.000 33 C₁₅H₁₆N₂O₂S 289.100 289.101 -3.459 34 C15H15NO2S 274.089 274.090 -3.648 35 C₁₅H₁₆N₂OS 273.105 273.106 -3.66 36 C15H16N2OS 273.105 273.106 -3.66 37 C₁₅H₁₅NO₄S 306.079 306.079 0.000 38 C15H15NO3S 290.084 290.084 0.000 39 C₁₅H₁₆N₂O₂S 289.100 289.101 -3.458 40 C16H18N2O2S 303.116 303.116 0.000 41 C₁₅H₁₅FN₂O₃S 323.086 323.086 0.000 42 C15H15FN2O2S 307.092 307.091 3.256 43 C₁₅H₁₄FNO₃S 308.075 308.075 0.000 44 C15H14FNO2S 292.080 292.080 0.000 45 C₂₅H₃₂N₂O₃S 441.220 441.220 0.000 46 C25H32N2O4S 459.231 459.231 0.000 GAR-P04397WO09 Application (final)2.docx 47 C₂₅H₃₂N₂O₂S 425.225 425.226 -2.351 48 C25H34N2O3S 443.236 443.236 0.000 49 C₁₅H₁₅NO₃S 290.085 290.084 3.447 50 C15H15NO4S 306.079 306.079 0.000 51 C₁₅H₁₆N₂O₃S 305.095 305.095 0.000 52 C15H16N2O4S 321.090 321.090 0.000 Example 8: Liquid culture and handling for electro transformation and biparental conjugation Depending on the strain, a conjugation and selection process in liquid can also be advantageous. Overnight cultures of the recipient and donor strains were inoculated according to growth requirements. The next day, the donor strain was diluted 1:5 and the recipient 1:2 followed by further 2 hours of incubation. Then, 200 µl of the donor was mixed with 800 µl of the recipient in a 2 ml reaction tube. The suspension is subsequently pelleted, and washed twice with 1 ml of growth medium LB with counterselection agent, i.e. 50 µg/ml ALA. Finally, 300 µl of LB containing 50 µg/ml ALA is left over the pellet and incubated overnight at 30 degrees without agitation. The following day, the cell pellet was washed and resuspended in 1 ml LB. The entire cell mass was then added to selection plates containing positive selection agent, i.e.50 µg/ml Km, and without ALA in order to select only for mutated recipient strains and counterselecting for donor strains. Example 9: High-throughput conjugation For high-throughput conjugation of pAR20 plasmids into recipient strains, the robot Rotor + system from Singer was used. Overnight cultures of donor strains were grown 10 ml LB containing 50 µg/ml Km and 50 µg/ml ALA acid in 96 well deep well plates. The culture was pelleted the next day and washed twice with ddH2O. Subsequently, the pellet was resuspended in 100 µl LB and the suspension was spotted robotically in 7x7 patches to a LB agar plate containing 50 µg/ml ALA (Figure 15B). The same procedure was used for the recipient spotted on top of donor strains. After overnight incubation at 30 °C, patches were scraped through the Singer ROTOR+ benchtop robot and transferred to microtiter plates containing 100 µl LB with 25 µg/ml Km. After further incubation overnight, the suspension was spotted through the ROTOR+ onto LB agar containing 25 µg/ml Km. Colonies were visible after 1 - 2 days depending on the strain. GAR-P04397WO09 Application (final)2.docx Example 10: Culture of strains after CRISPR/Cpf1 assisted gene editing. For fluorescent reporter insertion/BGC replacement, or genome editing such as GR deletion or promoter exchange or BGC replacement, a strain carrying a specific pAR20 vector was inoculated as a 5 ml overnight culture in a 50 ml Erlenmeyer flask. The next day, this culture was diluted to a final OD of 0.5 in 10 ml LB containing 25 µg/ml Km. The culture was then incubated at 30 °C until an OD of 0.8 - 1.0 was reached. After addition of AHT to induce expression of the Cpf1 protein, the culture was further incubated at 25 °C for 1h. Subsequently, L- arabinose (0.4%) was added and incubated for another 3 h at the same temperature. Finally, 50 µl of the cell suspension was plated on a selection plate with Km and arabinose to induce expression of lambda red proteins. Edited colonies were visible after 2 days. Example 11: Screening in high-throughput format of mutated bacteria This Example describes selection in high-throughput format (Figure 15A), i.e. in 96-well microplates or higher, of bacteria, which have been mutated by experiments of CRISPR/Cpf1 mediated genetic replacement, or deletion, and can be adapted to random mutagenesis, or transposon mutagenesis generated mutants. For high-throughput genome editing, the strains carrying gene-specific CRISPR/Cpf1 -pAR20 were inoculated in a 1 ml overnight culture in 96 deep well plates. The next day, the cultures were diluted 1:25 in 100 µl fresh LB containing 25 µg/ml Km in 96-well microtiter plates (e.g. Greiner Flat bottom plates). Growth was monitored by incubation in a Tecan microtiter plate reader (Tecan Spark). The absorbance at 595 nm was measured every 15 minutes while the plate was incubated at 220 rpm at 30 °C between measurements. Once the absorbance doubled relative to the initial value, Cpf1 expression inducer AHT was added, the incubation temperature lowered to 25 °C and the plate was then incubated at 220 rpm. After another hour of incubation, L-arabinose was added and plates were incubated for another 3 hours. After the incubation period, two dilutions (1:4 and 1:20) of the original cultures were prepared in microtiter plates. From these dilutions, 20 µl each was spotted onto the top of a rectangular agar plate (containing 25 µg/ml Km and 0.4 % arabinose) using a 12-channel multichannel pipette. By placing the plate vertically, the spot was "spread" downwards in a strip and thereby indirectly diluted (Figure 16 A,B,C). Individual colonies were selected after 2 days of growth at 30°C in the dark and verified by colony PCR. GAR-P04397WO09 Application (final)2.docx Example 12: Activation of the Xenoamicin (xab) BGC in Xenorhabdus doucetiae ΔcyaA To test the utility of the global regulator cyaA discovered by the above described method, cyaA was deleted in Xenorhabdus doucetiae based on pAR20 targeted gene deletion. CyaA specific HA-L and R (SEQ ID NOs 187-188) were used as synthetic dsDNA fragments for CRISPR/Cas12 mediated genome editing for this approach. This was followed by replacing the native promotor upstream of the known BGC related to the biosynthesis of Xenoamicin A (30, Figure 22A) in the cyaA deletion mutant and the wild type. This was achieved by the promoter exchange method based on pAR20 using the the vanillic acid inducible promoter (SEQ ID NO 131) and the xabA specific HA-L and R SEQ ID NOs 189-190. Production was compared between the cyaA mutant and the wild type (Figure 22B). Example 13: Construction of multi-producers of natural product classes with desired bioactivities. Following the identification of BGCs with desired bioactivities as described in Examples 3 - 7 (see above), the activatable BGCs can be combined following the inventive methods for promoter exchange and refactoring (see Examples 5 - 7) in a single strain, leading to strains producing exclusively and only metabolites with desired bioactivities, like antibiotic, antifungal, nematicidal (or any other) activity (Figure 18). These bacterial strains can be used to generate extracts or compound mixtures with superior bioactivity than the individual metabolites alone and can be applied in medicine, animal health and agriculture. Such a multi-producer strain (or an extract derived thereof) has the advantage of being easier to handle compared to culture of several mono-producing strains or handling of many extracts of individual compounds to be combined. Example 14: Activation of the silent BGC dpr (deoxy-puromycin) in Xenorhabdus nematophila To further confirm the method developed by the inventor, a promoter exchange was performed in a global regulator cyaA and or hfq deficient mutant of Xenrohabdus nematophila upstream of the silent BGC dpr (Figure 20A). Deletion of the GRs were done with the pAR20 system, with the: Δhfq specific HA-L and R having SEQ ID NOs 181-182 or ΔcyaA specific HA-L and R having SEQ ID NO 183.184. The activation of the dprA BGC by insertion of the Pvan promoter (SEQ ID NO 131) upstream of dprA was done together with the dprA specific HA-L and R having SEQ ID NO 185 - 186, also based on the pAR20 editing system. GAR-P04397WO09 Application (final)2.docx The activation of BGC led to the production of different derivatives in different culture media in Sf900: M1 (m/z = 442 [M+H]⁺), M2 (m/z = 484 [M+H]⁺) and in XPPM: M2 (m/z = 484 [M+H]⁺), M3 (m/z = 470 [M+H]⁺) (Figure 20B). In Sf900, M1 was the major product and M2 as a byproduct. M3 was not detectable at all. When cultured in XPPM medium M2 was the main product and M3 was present as a byproduct. M1 was not produced.In order to determine a molecular formula, cultivation was carried out in ¹³C and ¹⁵N medium (ISOGRO®-13C Powder - Growth Medium; ISOGRO®-15N Powder -Growth Medium). The MS/MS spectra are shown in Figure 20C. Using the data from Figure 20C, mass shifts could be assigned to several mass signals. The altered masses result from the incorporation of heavy ¹³C/¹⁵N isotopes into the respective molecule, whereby the magnitude of the shift correlates with the number of isotopes incorporated. In this way, the molecular formula of M1 was determined as C21H27N7O4. According to the feeding experiments, the structures for the masses M1 to M3 could be confirmed by NMR and named as follows: Demethoxypuromycin (M1, 27), N- acetyl-demethoxypuromycin (M2, 28) and N-formyl-demethoxypuromycin (M3, 29) (Figure 21A-C, Table 15 below). Table 15 M1 (441Da) Position δ_H (mult., J) δ_C (mult., J) Adenin 2 8.24 (s) 152.3, CH 4 - 150.1, C 5 - 120.1, C 6 - 154.7, C 8 8.45(s) 138.3, CH Ribose 10 5.99 (d, 2.7) 89.8, CH 11 4.51 (dd, 5.8, 2.8) 73.5, CH 12 4.47 (m) 50.8, CH 13 3.92 (m) 83.8, CH 14 3.67 (dd, 12.2, 2.2) 61.3, CH₂ 3.45 (dd, 12.2, 4.1) Phe 16 - 171.2, C 17 3.75 (ddd, 6.9) 55.6, CH 18 3.02 (dd, 13.5, 6.0) 38.6, CH2 2.78 (dd, 13.5, 8.0) 19 - 137.9, C 20 7.25 (m) 129.8, CH 21 7.30 (m) 128.7, CH 22 7.21 (m) 126.9, CH GAR-P04397WO09 Application (final)2.docx 23 7.30 (m) 128.7, CH 24 7.25 (m) 129.8, CH 25 8.35 (s) - M₂ (483Da) Position δH (mult., J) δC (mult., J) Adenin 2 8.24 (s) 152.3, CH 4 - 150.1, C 5 - 120.1, C 6 - 154.7, C 8 8.45(s) 138.3, CH Ribose 10 6.01 (d, 3.1) 89.8, CH 11 4.52 (dd, 5.9, 3.1) 73.5, CH 12 4.48 (m) 50.8, CH 13 3.94 (m) 83.8, CH 14 3.67 (dd, 12.2, 2.1) 61.3, CH2 3.46 (dd, 12.2, 4.0) 15 8.22 (d, 7.8) - Phe 16 - 171.2, C 17 4.66 (ddd, 8.2, 7.2, 4.0) 54.4, CH 18 2.99 (dd, 13.6, 5.3) 38.6, CH2 2.79 (dd, 13.6, 9.4) 19 - 138.3, C 20 7.27 (m) 129.7, CH 21 7.27 (m) 128.5, CH 22 7.19 (m) 126.7, CH 23 7.27 (m) 128.5, CH 24 7.27 (m) 129.7, CH 25 8.17 (d, 8.4) - 26 - 169.6, C 27 1.77 (s) 22.9, CH₃ M₃ (469Da) Position δH (mult., J) δC (mult., J) Adenin 2 8.24 (s) 152.3, CH 4 - 150.1, C 5 - 120.1, C 6 - 154.7, C 8 8.45(s) 138.3, CH Ribose 10 6.00 (d, 3.0) 89.8, CH 11 5.19 (dd, 5.1) 73.5, CH 12 4.49 (m) 50.8, CH GAR-P04397WO09 Application (final)2.docx 13 3.94 (m) 83.8, CH 14 3.67 (d, 10.9) 61.3, CH₂ 3.47 (m) 15 8.29 (m) - Phe 16 - 171.2, C 17 4.66 (ddd, 5.3, 8.9) 52.7, CH 18 2.99 (dd, 13.7, 5.2) 38.6, CH₂ 2.79 (dd, 13.7, 9.2) 19 - 137.9, C 20 7.28 (m) 129.7, CH 21 7.28 (m) 128.5, CH 22 7.20 (m) 126.8, CH 23 7.28 (m) 128.5, CH 24 7.28 (m) 129.7, CH 25 6.08 (d, 3.9) - 26 7.93 (d, 0.9) 161.2, C GAR-P04397WO09 Application (final)2.docx

Claims

Claims 1. A method to elicit production of a secondary metabolite by a bacterium, wherein the method comprises the following steps: i) deleting a global regulator (GR) gene in said bacterium, and ii) optionally activating a biosynthetic gene cluster (BGC) involved in production of said secondary metabolite in said bacterium; or wherein the method comprises the following steps: i') essentially activating a biosynthetic gene cluster (BGC) involved in production of said secondary metabolite in said bacterium, and ii') optionally deleting a GR gene in said bacterium; and the method further comprises: iii) expressing in said bacterium at least one positive selectable marker gene and at least one negative selectable marker gene; wherein deleting a GR gene of steps i) or ii') comprises introducing in said bacterium at least one GR specific siRNA, or a group of sequences comprising a Cas gene, at least one GR specific crRNA array, a pair of GR specific homology regions left and right; and/or wherein activating a BGC of steps ii) or i') comprises introducing in said bacterium a group of sequences comprising a Cas gene, at least one BGC specific crRNA array, a pair of BGC specific homology regions left and right, a promoter system, and optionally an enhancer sequence. 2. The method according to claim 1, wherein step ii) or step i') comprises activating at least 2 BGCs in said bacterium. 3. The method according to claim 1 or 2, wherein the GR gene is cyaA gene. 4. The method according to any one of the claims 1 – 3, wherein said BGC is selected from the group comprising puromycin, madumycin II, xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives. 5. The method according to any one of the claims 1 – 4, wherein the GR gene is cyaA gene and said BGC is xenoamicin. 6. The method of any one of the claims 1 – 5, wherein the step i) - iii) are performed using an automated liquid handling robotics, and wherein said GAR-P04397WO09 Application (final)2.docx robotics enables high-throughput manipulation of liquid added to or removed from cultures comprising the bacteria. 7. A method for screening for a global regulator (GR) gene in a bacterium, the method comprising: a) replacing a gene sequence of a first constitutively expressed biosynthetic gene cluster (BGC) with a first fluorescent reporter gene; b) replacing a gene sequence of a second constitutively expressed BGC with a second fluorescent reporter gene, wherein the first and second fluorescent reporters emit two non-overlapping fluorescent signals; c) obtaining a bacterium indicator strain emitting the first and the second fluorescent signals; d) performing random mutagenesis in said bacterium indicator strain to generate random mutations; e) screening and identifying non-fluorescent mutant bacteria that do not emit the first and the second fluorescent signal, f) isolating said non-fluorescent mutant bacteria, g) performing whole genome sequencing of said non-fluorescent mutant bacterium to map the mutations generated in step d); h) identifying the mutations generated in a GR gene, wherein said GR gene regulates the activity of the first constitutively expressed BGC and of the second constitutively expressed BGC in said bacterium; wherein the replacing of a gene sequence of a BGC at step a) and b) does not disrupt a regulatory element of said BGC; wherein in step a) and b) the reading frame is conserved; wherein said GR gene regulates production of a target secondary metabolite. 8. The method of claim 7, wherein step e) is performed by fluorescence activated cell sorting, fluorescence spectroscopy, stereo microscopy, or fluorescence imaging. 9. The method of claim 7 or 8, further comprising after step h), the following step i): i) screening for production of secondary metabolites regulated by said GR gene by HPLC / mass spectrometry analysis. 10. The method of any one of the claims 7 – 9, wherein performing random mutagenesis of step d) comprises chemical random mutagenesis, or UV- GAR-P04397WO09 Application (final)2.docx mediated random mutagenesis, or error-prone PCR or transposon mutagenesis. 11. The method of any one of the claims 7 – 10, wherein said BGC of step a) and/or b) encodes an enzyme responsible for production of secondary metabolites, wherein the enzyme is selected from the group comprising non- ribosomal peptide synthetase, terpene synthase/cyclase, polyketide synthase, ribosomally produced peptide (RiPP). 12. The method of any one of the claims 7 – 11, wherein the secondary metabolite is an antibiotic, or an anti-cancer drug, or an immune suppressive drug and is preferably selected from the group comprising Puromycin, Madumycin II, Xenoamicin, rupshomycin, rupshomycin derivatives, safracin, safracin derivatives. 13. The method of any one of the claims 7 – 12, wherein the bacterium is not Streptomyces. 14. The method of any one of the claims 7 – 13, wherein the bacterium is selected from the group comprising Xenorhabdus, Photorhabdus, Pseudomonas, Serratia, Vibrio, myxobacteria, cyanobacteria, Bacillus, and Paenibacillus. 15. The method of any one of the claims 7 – 14, wherein the steps a) and b) are performed introducing in said bacterium a Cas gene, a first and second constitutively expressed BGC specific crRNA arrays, a first and second fluorescent reporter gene, and a first and second pair of BGC specific homology regions left and right. 16. A compound of general formula (I)

wherein Y represents –CH=CH2 or ; GAR-P04397WO09 Application (final)2.docx R¹, R², R³, R⁴, and R⁵ are independently of each other selected from –H, –NH2, –NHR⁶, –F, –OH, –OCH3, –OCH2CH3, and –OCH2CH2CH3; or R² and R³ or R³ and R⁴ together with the carbon atom to which they are bound to form one of the following rings:

with the proviso that when Y represents –CH=CH2, R¹, R², R⁴, and R⁵ cannot be –H, and R³ cannot be –OH simultaneously. 17. The compound according to claim 16 having the following structure

wherein Y, and R¹ – R⁵ have the meanings as defined in claim 16. 18. The compound according to claim 16 having the following structure

wherein Y, and R¹ – as in claim 16. GAR-P04397WO09 Application (final)2.docx 19. The compound according to claim 16 selected from the group consisting of:

GAR-P04397WO09 Application (final)2.docx 20. The compound according to claim 19, wherein the compound is a (2E)- thiazolidine isomer. 21. The compound according to claim 19, wherein the compound is a (2Z)- thiazolidine isomer. GAR-P04397WO09 Application (final)2.docx