Polyphasic taxonomic description of Streptomyces okerensis sp. nov. and Streptomyces stoeckheimensis sp. nov. and their biotechnological potential

<i>Streptomyces</i> strains DSM 116494^T and DSM 116496^T were isolated from sediment samples of the River Oker in Braunschweig, Germany, and subjected to a polyphasic taxonomic study and genome mining for specialized secondary metabolites. Phenotypic, genetic and genomic data confirmed the assignment of these strains to the <i>Streptomyces</i> genus. Pairwise 16S rRNA gene sequence similarity values between the strains and validly named <i>Streptomyces</i> species reached 99.5 and 99.7% for strains DSM 116494^T and DSM 116496^T, respectively. Genome-based phylogeny demonstrated that <i>Streptomyces pilosus</i> and <i>Streptomyces griseoflavus</i> species were the close relatives to strain DSM 116494^T, while <i>Streptomyces vinaceus</i> species was the nearest neighbour to strain DSM 116496^T. Digital DNA-DNA hybridization and average nucleotide identity comparisons of the genomic sequence of the strains and their close phylogenomic relatives revealed that values were below the determined threshold of 70 and 95-96% for prokaryotic species demarcation, respectively. The strains were distinguished from their close neighbours based on biochemical, chemotaxonomic and enzymatic data. Given these results, the strains merit being affiliated to novel species within the genus <i>Streptomyces</i>, for which the names <i>Streptomyces okerensis</i> sp. nov. (=OG2.3^T=DSM 116494^T=KCTC 59408^T) and <i>Streptomyces stoeckheimensis</i> sp. nov. (=OG3.14^T=DSM 116496^T=KCTC 59410^T) are proposed. Strains DSM 116494^T and DSM 116496^T harboured several biosynthetic gene clusters encoding potentially novel antimicrobial and anticancer compounds. Crude extracts of strains DSM 116494^T and DSM 116496^T inhibited the growth of Gram-negative bacteria (<i>Escherichia coli</i> ΔtolC, <i>Proteus vulgaris</i>) and a multi-drug-resistant Gram-positive, <i>Staphylococcus aureus</i>.