Reclassification of Streptomyces rimosus subsp. paromomycinus as Streptomyces paromomycinus sp. nov.

Streptomyces rimosus is currently composed of two subspecies: Streptomyces rimosus subsp. rimosus and Streptomyces rimosus subsp. paromomycinus. The 16S rRNA gene similarity between type strains of these two subspecies is 99.03 %, whereas that between S. rimosus subsp. paromomycinus and Streptomyces chrestomyceticusis 100 %. To assess the taxonomic status of S. rimosus subsp. paromomycinus, genome sequencing was performed on the type strains of S. rimosus subsp. paromomycinus and S. chrestomyceticus. Digital DNA-DNA hybridization values between S. rimosus subsp. paromomycinus NBRC 15454T and S. rimosus subsp. rimosus ATCC 10970T and between S. rimosus subsp. paromomycinus NBRC 15454T and S. chrestomyceticus NBRC 13444T were 35.4 and 59.9 %, respectively, which are less than the thresholds for bacterial species delineation and indicate that S. rimosus subsp. paromomycinus is not S. rimosus, but an independent species different from S. rimosus and S. chrestomyceticus. In addition, phenotypic data also support that S. rimosus subsp. paromomycinus is distinct from S. chrestomyceticus. Therefore, S. rimosus subsp. paromomycinus should be reclassified as a novel species, for which we propose the name Streptomyces paromomycinus sp. nov. The type strain is NBRC 15454T (=ATCC 14827T=DSM 41429T=JCM 4541T=JCM 4871T=NRRL 2455T=VKM Ac-605T).