Polyphasic Taxonomy of Glacier-Derived Arthrobacter Strains Reveals Six Novel Species Within the Arthrobacter Agilis Group and Indicates Arthrobacter Vasquezii Valenzuela-Ibaceta Et Al. 2023 As a Later Heterotypic Synonym of Arthrobacter Parietis Heyrman Et Al. 2005.

Eight bacterial strains assigned to the genus Arthrobacter by preliminary 16S rRNA gene screening were isolated from supraglacial samples collected from four glaciers in China. Genome-based analyses provided the primary evidence for species delineation. Pairwise average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) comparisons among the eight strains and between the glacier-derived strains and their closest type-strain relatives supported their assignment to six novel species, with strains HZ1T and HLT1-21 (ANI 99.1%, dDDH 92.2%) and strains MDB2-24T and MDT3-44 (ANI 98.5%, dDDH 87.9%) each representing a single genomic species. Consistently, a maximum-likelihood phylogenomic tree inferred from 81 concatenated bacterial core genes resolved 6 well-supported independent species-level lineages within the Arthrobacter agilis group. The predominant cellular fatty acid of the representative strains was anteiso-C15 : 0 (34.5-66.1%). In addition, genome-relatedness indices indicated that Arthrobacter vasquezii Valenzuela-Ibaceta et al. 2023 is conspecific with Arthrobacter parietis Heyrman et al. 2005 (ANI 98.8%, dDDH 90.1%) and should, therefore, be treated as a later heterotypic synonym of A. parietis Heyrman et al. 2005 under the principle of priority. Based primarily on phylogenomics and genome relatedness, supplemented by phenotypic and chemotaxonomic characterization, the eight strains represent six novel species of the genus Arthrobacter, for which the following names are proposed: Arthrobacter glycogeni sp. nov. (HZ1T=CGMCC 1.9261T=JCM 38152T), Arthrobacter arabinosi sp. nov. (TMS1-12-1T=CGMCC 1.9392T=NBRC 113087T), Arthrobacter melezitosi sp. nov. (TMN-37T=CGMCC 1.9692T=JCM 38156T), Arthrobacter sorbitolis sp. nov. (MDT1-65T=CGMCC 1.9836T=JCM 38163T), Arthrobacter rhamnosi sp. nov. (MDB2-24T=CGMCC 1.9862T=JCM 38160T) and Arthrobacter pasteuri sp. nov. (MDT2-2T=CGMCC 1.9874T=JCM 38164T).