Taxonomic rearrangement of Salinibacterium, Leifsonia, Diaminobutyricibacter, Antiquaquibacter, Homoserinimonas and Glaciibacter: refining genus boundaries and proposal of two new genera – Orlajensenia gen. nov. and Leifsonella gen. nov.

Abstract

The actinobacterial family Microbacteriaceae comprises a diverse group of Gram-positive bacteria with high G+C content and complex taxonomic challenges. Traditional polyphasic approaches, based on 16S rRNA phylogeny and phenotypic traits, have in some instances resulted in polyphyletic taxonomic groupings, necessitating genome-wide methodologies to better resolve evolutionary relationships. This study employs a taxogenomic approach – incorporating 16S rRNA gene sequencing, core protein phylogeny, average amino acid identity and percentage of conserved proteins – to reassess the genera Leifsonia , Salinibacterium , Homoserinimonas , Glaciibacter , Antiquaquibacter and Diaminobutyricibacter . The findings reveal significant polyphyly in Leifsonia , Glaciibacter and Salinibacterium , indicating ecological convergence rather than shared ancestry. Proposed taxonomic revisions include the reclassification of Salinibacterium soli and Salinibacterium metalliresistens into Antiquaquibacter , Salinibacterium hongtaonis and Salinibacterium sedimenticola into Homoserinimonas , and Leifsonia psychrotolerans and Leifsonia kafniensis into Glaciibacter . Diaminobutyricibacter tongyongensis should be incorporated into Leifsonia . Additionally, Leifsonia rubra is reassigned to Salinibacterium . Two new genera were also proposed to encompass “Leifsonia flava” and Glaciibacter flavus , named Orlajensenia gen. nov. and another to encompass Leifsonia bigeumensis , named Leifsonella gen. nov. These genome-based insights provide a refined framework for the taxonomy of Microbacteriaceae , enhancing our understanding of their evolutionary and ecological roles.