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 BI20^T, isolated from the rhizosphere of <i>Dryopteris marginalis</i>, was subjected to a polyphasic taxonomic study. Analysis of the 16S rRNA gene sequence showed that strain BI20^T belonged to the genus <i>Streptomyces</i> and shared the highest sequence similarities to Streptomyces cinnamoneus JCM 4633^T (98.75%), <i>Streptomyces hiroshimensis</i> JCM 4586^T (98.74%) and <i>Streptomyces pseudoechinosporeus</i> NBRC 12518^T (98.68%). Phylogenetic analysis based on 16S rRNA gene and whole-genome sequences indicated that strain BI20^T was most related to <i>Streptomyces laurentii</i> ATCC 31255^T. However, the average nucleotide identity by MUMmer (ANIm) and digital DNA-DNA hybridization (dDDH) values between strain BI20^T and the above four <i>Streptomyces</i> 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 BI20^T contained <i>ll-</i>diaminopimelic acid and whole-cell sugars contained glucose. The predominant cellular fatty acids (>10%) were <i>anteiso-</i>C_{15 : 0}, <i>iso-</i>C_{15 : 0}, <i>iso-</i>C_{16 : 0} and C_{16 : 0}. All these data indicated that strain BI20^T represents a novel <i>Streptomyces</i> species, for which the name <i>Streptomyces dryopteridis</i> sp. nov. is proposed. The type strain is strain BI20^T (=MCCC 1K09588^T=JCM 38134^T). In addition, we propose that <i>Streptomyces cuspidosporus</i> Higashide <i>et al</i>. 1966 (Approved Lists 1980) is a later heterotypic synonym of <i>Streptomyces sparsogenes</i> Owen <i>et al</i>. 1963 (Approved Lists 1980) based on comparative genomic analysis. Meanwhile, based on the dDDH value, <i>S. sparsogenes</i> and <i>S. cuspidosporus</i> are simultaneously designated as two different subspecies, i.e. <i>S. sparsogenes</i> subsp. <i>sparsogenes</i> and <i>S. sparsogenes</i> subsp. <i>cuspidosporus</i>.