Reclassification of four subspecies in the genus Streptomyces to Streptomyces rubradiris sp. nov., Streptomyces asoensis sp. nov., Streptomyces fructofermentans sp. nov. and Streptomyces ossamyceticus sp. nov.

The genus Streptomyces includes, at the time of writing, eight subspecies with validly published names. Streptomyces thermoviolaceus subsp. apingens NBRC 15459T and Streptomyces lavendulae subsp. grasserius NBRC 13045T show 16S rRNA gene sequence similarities of >99.7% to their parent species Streptomyces thermoviolaceus subsp. thermoviolaceus NBRC 13905T and Streptomyces lavendulae subsp. lavendulae NRRL B-2774T, respectively. In contrast, the type strains of the remaining six subspecies, Streptomyces achromogenes subsp. rubradiris, Streptomyces albosporeus subsp. labilomyceticus, Streptomyces cacaoi subsp. asoensis, Streptomyces chrysomallus subsp. fumigatus, Streptomyces cinereoruber subsp. fructofermentans and Streptomyces hygroscopicus subsp. ossamyceticus, do not show >99.0% 16S rRNA gene sequence similarity to that of each parent species. Although S. chrysomallus subsp. fumigatus and S. hygroscopicus subsp. ossamyceticus were respectively reclassified to 'Kitasatospora fumigata' and 'Streptomyces ossamyceticus', these names have not been validly published yet. In this study, we investigated the taxonomic positions of S. achromogenes subsp. rubradiris, S. cacaoi subsp. asoensis, S. cinereoruber subsp. fructofermentans, S. hygroscopicus subsp. ossamyceticus and S. thermoviolaceus subsp. apingens given that their whole genome sequences are available. Except for S. thermoviolaceus subsp. apingens, these subspecies were discriminated from the parent and closely related species based on phylogenetic, genomic and phenotypic differences. Thus, we reclassify S. achromogenes subsp. rubradiris, S. cacaoi subsp. asoensis, S. cinereoruber subsp. fructofermentans and S. hygroscopicus subsp. ossamyceticus as Streptomyces rubradiris sp. nov., Streptomyces asoensis sp. nov., Streptomyces fructofermentans sp. nov. and Streptomyces ossamyceticus sp. nov., respectively. Multilocus sequence and 16S rRNA gene sequence analyses suggested that S. albosporeus subsp. labilomyceticus and S. lavendulae subsp. grasserius may also be reclassified as independent species.