Classification and Secondary Metabolite-Biosynthetic Gene Clusters of Marine Streptomyces Strains Including a Lobophorin- and Divergolide-Producer

Two Streptomyces strains, named N11-26 and DC10-5, were isolated from deep-sea and non-photosynthetic stony coral, respectively. Strain N11-26 produces lobophorin C and divergolides, which are antimicrobial substances. This study aimed to classify these strains and reveal their cryptic potential to synthesize other secondary metabolites, such as polyketides and nonribosomal peptides. Strains N11-26 and DC10-5 showed 16S rRNA gene sequence similarities of 100% and 99.9% to Streptomyces olivaceus NRRL B-3009T, respectively. By digital DNA–DNA hybridization using whole-genome sequences, these strains were classified as Streptomyces olivaceus. Strain N11-26 was closer to the type strain of S. olivaceus than strain DC10-5 and possessed 17 clusters of polyketide synthase (PKS) and/or nonribosomal peptide synthetases (NRPS) genes, whereas strain DC10-5 harbored 19 clusters. Putative products by these gene clusters were predicted by bioinformatic analyses. Although 15 clusters were conserved between the two strains, two and four clusters were specific in strains N11-26 and DC10-5, respectively. This represents a diversity of potential polyketide and nonribosomal peptide compounds between strains of S. olivaceus. To the best of our knowledge, this is the first report annotating all the PKS and NRPS gene clusters in S. olivaceus strains with their putative products to provide useful information for genome mining.