Department of Biotechnology, Yeungnam University, Gyeongsan, Gyeongbuk 38541, Republic of Korea.
Res Microbiol. 2023 Jun;174(5):104057. doi: 10.1016/j.resmic.2023.104057. Epub 2023 Apr 8.
The order Nevskiales, class Gammaproteobacteria, encompasses four families Algiphilaceae, Salinisphaeraceae, Nevskiaceae, and Steroidobacteraceae. The taxonomy of this order is structured from the inferences derived from the 16S rRNA gene and genome-based phylogenetic tree analyses. However, previous taxonomic studies of the order failed to incorporate most of the representatives from other established orders within the class Gammaproteobacteria. Other divergent members within the class Gammaproteobacteria were therefore overlooked. In this study, the taxonomy of the order Nevskiales was revisited using genome-based analyses with an expanded scope of outgroups representing the vast majority of the diversity within the class Gammaproteobacteria. Results from the phylogenetic analyses strongly supported the exclusion of the family Steroidobacteraceae from the order Nevskiales and further implied the assignment of the family into a novel order. In addition, the analyses also supported the reclassification of Steroidobacter gossypii, Steroidobacter soli, Steroidobacter agariperforans, and Steroidobacter agaridevorans into a novel genus. The identified conserved signature indels in 33 protein sequences further reinforced the new taxonomic assignments. Furthermore, the results of the average nucleotide identity and average amino acid identity analyses, together with the phenotypic and genomic characteristics among the members of the genus Steroidobacter also provided evidence supporting the reclassification of the four Steroidobacter species. Based on these results, the family Steroidobacteraceae is proposed to be assigned to a novel order Steroidobacterales ord. nov., and the species S. gossypii, S. soli, S. agariperforans, and S. agaridevorans are proposed to be moved to a novel genus Peristeroidobacter gen. nov. within the family Steroidobacteraceae.
内夫斯基菌目，γ-变形菌纲，包含四个科：噬盐菌科、盐球菌科、内夫斯基菌科和甾体杆菌科。该目的分类是基于 16S rRNA 基因和基于基因组的系统发育树分析的推断得出的。然而，以前对内夫斯基菌目的分类研究未能将大多数来自γ-变形菌纲内其他已建立目的代表纳入其中。因此，其他具有不同特征的γ-变形菌纲成员被忽略了。在本研究中，使用基于基因组的分析方法，扩大了外群的范围，代表了γ-变形菌纲内的绝大多数多样性，重新研究了内夫斯基菌目的分类。系统发育分析的结果强烈支持将甾体杆菌科排除在内夫斯基菌目之外，并进一步暗示将该科归入一个新目。此外，分析结果还支持将 Steroidobacter gossypii、Steroidobacter soli、Steroidobacter agariperforans 和 Steroidobacter agaridevorans 重新分类为一个新属。在 33 个蛋白质序列中鉴定的保守特征缺失进一步加强了新的分类分配。此外，平均核苷酸同一性和平均氨基酸同一性分析的结果，以及 Steroidobacter 属成员之间的表型和基因组特征，也为这四个 Steroidobacter 种的重新分类提供了证据。基于这些结果，建议将 Steroidobacteraceae 科分配到一个新目的 Steroidobacterales ord. nov.，并将 S. gossypii、S. soli、S. agariperforans 和 S. agaridevorans 物种移至 Steroidobacteraceae 科内的一个新属 Peristeroidobacter gen. nov.。
