Integrated genomic analyses support the reclassification of Arthrobacter vasquezii Valenzuela-Ibaceta et al. 2023 as a later heterotypic synonym of Arthrobacter parietis Heyrman et al. 2005

The genus Arthrobacter Conn and Dimmick 1947 (Approved Lists 1980) encompasses a large and taxonomically complex assemblage of species within the family Micrococcaceae , many of which were described before whole-genome sequencing became a routine practice of prokaryotic taxonomy. During a comparison of genome sequences of Arthrobacter type strains, the type strain of Arthrobacter vasquezii Valenzuela-Ibaceta et al. 2023 (EH-1B-1 ^T ), isolated from Antarctic soil, was found to be genomically indistinguishable from the type strain of Arthrobacter parietis Heyrman et al. 2005 (LMG 22281 ^T ), isolated from a deteriorated mural painting. Pairwise comparison of the two type-strain genome sequences yielded a digital DNA–DNA hybridization (dDDH) value of 90.1% (95% CI 87.8–92.0%), an average nucleotide identity (ANI) of 98.96% and an average amino acid identity (AAI) of 99.15%, all well above the accepted thresholds for species delineation (dDDH ≥70%; ANI/AAI ≥95–96%). This congruence is further supported by all 16S rRNA gene sequence-based tree topologies and core genome phylogenomics and is consistent with comparative carbohydrate-active enzyme profiling and phenotypic analyses. As A. parietis Heyrman et al. 2005 has nomenclatural priority, we propose that A. vasquezii Valenzuela-Ibaceta et al. 2023 be reclassified as its later heterotypic synonym.