Reassessment of the status of Streptomyces setonii and reclassification of Streptomyces fimicarius as a later synonym of Streptomyces setonii and Streptomyces albovinaceus as a later synonym of Streptomyces globisporus

Abstract

The 16S rRNA and gyrB genes of 22 Streptomyces strains belonging to the Streptomyces griseus cluster were sequenced, and their taxonomic positions were re-evaluated. For correct analysis, all of the publicly available sequences of the species were collected and compared with those obtained in this study. Species for which no consensus sequence could be identified were excluded from the phylogenetic analysis. The levels of 16S rRNA gene sequence similarity within the cluster ranged from 98.6 to 100 % with a mean value of 99.6±0.3 %, and those of the gyrB gene ranged from 93.6 to 99.9 % with a mean value of 96.3±1.5 %. The observed average nucleotide substitution rate of the gyrB gene was ten times higher than that of the 16S rRNA gene, showing a far higher degree of variation. Strains sharing 99.3 % or more gyrB sequence similarity (corresponding to an evolutionary distance of 0.0073) always formed monophyletic groups in both trees. Through the combined analysis of the two genes, clear cases of synonymy could be identified and, according to the priority rule, the assertion of the status of Streptomyces setonii as a distinct species and the reclassification of Streptomyces fimicarius as a later synonym of S. setonii and Streptomyces albovinaceus as a later synonym of Streptomyces globisporus are proposed. Emended descriptions of S. setonii and S. globisporus are provided.

Reclassification of Streptomyces fulvissimus as a later heterotypic synonym of Streptomyces microflavus

“…For example, S. griseus and Streptomyces setonii were once considered to be the same species [5, 6] but later they were validly recognized as independent species again [7]. DNA–DNA relatedness is currently used as the ultimate means to define bacterial species [8, 9].…”

Antifungal Activity and Biosynthetic Potential of New Streptomyces sp. MW-W600-10 Strain Isolated from Coal Mine Water

“…The maximum-likelihood phylogenetic tree generated based on the strain’s core proteomes showed that the closest relatives of the MW-W600-10 strain are S. fimicarius NRRL ISP-5322 and S. baarnensis NRRL B-2842 ( Figure 1 ). Importantly, the phylogeny of the S. fimicarius NRRL ISP-5322 strain was revised recently, and it was suggested that the strain should be classified as S. setonii [ 51 ]. Here, we kept the taxonomical name of the NRRL ISP-5233 strain displayed in the NCBI database.…”

Antimicrobial potentiality of actinobacteria isolated from two microbiologically unexplored forest ecosystems of Northeast India

“…Four isolates (NNPR52, NNPR62, PWS6 and PWS52) had less than 98% similarity to its nearest known strain, which suggested that these isolates could be novel taxa [ 30 ] This is supported by the description of various phylogenetically similar (> 99%) Streptomyces strains as new and novel species [ 43 – 45 ]. Intragenomic heterogeneity, intraspecific disparity, inadequate resolution capacity and inconsistent DNA–DNA relatedness limit species-level delineation by 16S rRNA gene sequence data within the genus Streptomyces [ 46 – 48 ]. In fact, a definitive 16S rRNA gene sequence similarity threshold cannot be defined to describe whether an actinobacterium belonging to Streptomyces may or may not be a novel species [ 49 ].…”