Emended descriptions of Streptomyces javensis and Streptomyces rhizosphaericus based on reclassifications of Streptomyces yogyakartensis, Streptomyces cangkringensis, and Streptomyces indonesiensis.

Although some Streptomyces species share identical 16S rRNA gene sequences, their taxonomic relationships have not been adequately re-examined. Type strains of Streptomyces javensis, Streptomyces yogyakartensis and Streptomyces violaceusniger share the same 16S rRNA gene sequence. This study aimed to determine whether S. javensis, S. yogyakartensis and S. violaceusniger represent the same taxon using molecular and genome-based methods. Digital DNA-DNA hybridization revealed a relatedness of 89.4% between S. javensis JCM 11446^T and S. yogyakartensis JCM 11448^T, whereas the values for S. violaceusniger NBRC 13459^T to S. javensis JCM 11446^T and S. yogyakartensis JCM 11448^T were 53.7% and 55.1%, respectively. The type strains of S. javensis and S. yogyakartensis formed an independent clade in the phylogenomic tree, displaying similar phenotypes and sharing the same type I polyketide synthase (PKS) and nonribosomal peptide synthetase (NRPS) gene clusters. Accordingly, S. yogyakartensis was reclassified as a later heterotypic synonym of S. javensis. Furthermore, the phylogenomic tree suggested that Streptomyces rhizosphaericus JCM 11447^T, Streptomyces cangkringensis DSM 41769^T and Streptomyces indonesiensis DSM 41759^T may be synonymous. DNA-DNA relatedness among them ranged 97.1-98.4%. Additionally, these type strains showed similar phenotypes, and most of their type I PKS and NRPS gene clusters were conserved. Based on these results, S. cangkringensis and S. indonesiensis were reclassified as heterotypic synonyms of S. rhizosphaericus. Descriptions of S. javensis and S. rhizosphaericus were emended according to the reclassifications.