Screening of NRPS and PKS-I genes from secondary metabolite producer actinomycetes which were isolated from rhizosferic soils of Turkish endemic plants

Natural products are biological functionality and they are indispensible for drug discovery. Over 60% of the known microbial metabolites are produced by members of the order Actinomycetales, and the genus Streptomyces is reported as the most profilic producer of secondary metabolites. These structurally diverse metabolites include among antibiotics, antifungals, antitumor agents, antihelmintics and immunosuppresive agents. A broad range of biologically active peptide and polyketide compounds are syntesized by nonribozomal peptide synthetases (NRPS) and polyketide synthases (PKS-I), respectively. NRPS and PKS-I are biosynthetic systems involved in the synthesis of a large number of important biologically active compounds produced by actinomycetes.15 Streptomyces strains were previously isolated from rhizospheric soils of three Turkish endemic plants, identified, and antimicrobial activities were determined. In this study, NRPS and PKS-I genes were screened by using PCR approach in these local isolates. NRPS and PKS-I genes were amplified by degenerate PCR primers by using chromosomal DNAs from these isolates as templates. NRPS sequences were detected in all of the isolates while PKS-I sequences in 12 out of 15 the isolates. Putative NRPS and PKS-I fragments were cloned and mini libraries were constituted for NRPS and PKS-I from Streptomyces sp. CS41 and Streptomyces sp. CA17, respectively. According to BLAST analysis 6 different A domain belong to NRPS genes were detected in Streptomyces sp. CS41. It was observed that four domains of these have low homology below 70 % when compared to other NRPS genes reported so far. It was also determined that Streptomyces sp. CA17 has only one type PKS-I gene. It can be concluded that genes obtained from this study may be candidate new genes that are responsible for new bioactive compounds. This idea will be approved by hybridization studies in the genome of isolates in future works.