The screening of genes responsible for biosynthesis of the secondary metabolites from actinomycetes isolated from rhizospheric soils of endemic plants

Bioactive secondary metabolites are a functionally diverse class of biochemically synthesized compounds, which include antibiotics, antitumor agents, toxins, and siderophores. Microbial secondary metabolites represent a large source of compounds endowed with ingenious structure and potent biological activites. The actinomycetes traditionally represent one of the most impotant sources for the discovery of new metabolites with biological activity; and many of this are describe being produced by polyketide syntahases (PKS) and nonribosomal peptide synthetases (NRPS). The last decade, these biosyntetic genes (NRPSs, PKSs) are studied present a strain characterization system based on the metabolic potential of microbial strains by targeting. This method was applied to study the distribution of PKS and NRPS biosynthethetic systems in a collection of wild-type actinomycetes isolated from different habitats samples that were evaluated for the production of antimicrobial activites.In the present study, it was used 15 Streptomyces strain that were previously isolated from rhizospheric soil of endemic plants. The molecular characterization and antimicrobial activites of these strains were also previously determined. Nonribosomal Peptide Synthetase (NRPS) and type I Polyketide Synthase (PKS) genes were screened by polymerase chain reaction (PCR) in these strain. NRPS genes were amplified from all of 15 Streptomyces strains and type I PKS genes were detected in 14 out of 15 Streptomyces strain. PCR products of NRPS genes were cloned and constituted mini libraries from Stretomyces spp. AAH61, AR24, CA14 and BAH46. PCR products of type I PKS genes were cloned and constituted mini libraries from Streptomyces spp. CA3 and AS31. Sequence analyses of chosen clones were compared to the published sequences by performing BLAST search in the GenBank databases.According to BLAST analysis, three A domains belong to different NRPS genes were detected in both Streptomyces sp. AAH61 and Streptomyces sp. AR24. Furthermore, two different KS domains of type I PKS genes were detected in Streptomyces sp. AS31 and only one type I PKS gene was found in Streptomyces sp. CA3. It was observed that the sequences obtained from mini libraries have low homology when compared to the genes reported so far. Therefore, these genes may be candidate novel genes that are responsible for new bioactive compounds. This hypothesize will be approved by hybridization studies in the genome of isolates.