Streptomyces dryopteridis sp. nov., isolated from rhizosphere soil of Dryopteris marginalis and proposal of Streptomyces cuspidosporus Higashide et al. 1966 (Approved Lists 1980) as a later heterotypic synonym of Streptomyces sparsogenes Owen et al. 1963 (Approved Lists 1980).

A novel actinobacterium strain BI20T, isolated from the rhizosphere of Dryopteris marginalis, was subjected to a polyphasic taxonomic study. Analysis of the 16S rRNA gene sequence showed that strain BI20T belonged to the genus Streptomyces and shared the highest sequence similarities to Streptomyces cinnamoneus JCM 4633T (98.75%), Streptomyces hiroshimensis JCM 4586T (98.74%) and Streptomyces pseudoechinosporeus NBRC 12518T (98.68%). Phylogenetic analysis based on 16S rRNA gene and whole-genome sequences indicated that strain BI20T was most related to Streptomyces laurentii ATCC 31255T. However, the average nucleotide identity by MUMmer (ANIm) and digital DNA-DNA hybridization (dDDH) values between strain BI20T and the above four Streptomyces strains were 84.88-85.75% and 22.2-23.2%, respectively, well below 96.7% and 70% cut-off points recommended for delineating species. Whole-cell hydrolysates of strain BI20T contained ll-diaminopimelic acid and whole-cell sugars contained glucose. The predominant cellular fatty acids (>10%) were anteiso-C15 : 0, iso-C15 : 0, iso-C16 : 0 and C16 : 0. All these data indicated that strain BI20T represents a novel Streptomyces species, for which the name Streptomyces dryopteridis sp. nov. is proposed. The type strain is strain BI20T (=MCCC 1K09588T=JCM 38134T). In addition, we propose that Streptomyces cuspidosporus Higashide et al. 1966 (Approved Lists 1980) is a later heterotypic synonym of Streptomyces sparsogenes Owen et al. 1963 (Approved Lists 1980) based on comparative genomic analysis. Meanwhile, based on the dDDH value, S. sparsogenes and S. cuspidosporus are simultaneously designated as two different subspecies, i.e. S. sparsogenes subsp. sparsogenes and S. sparsogenes subsp. cuspidosporus.