Phylogenomic insights support the merger of the genera Mameliella and Maliponia into the genus Antarctobacter.

BACKGROUND: Members of the family Roseobacteraceae are metabolically, phenotypically, and genotypically diverse and are widely distributed in global marine environments. This family comprises over 150 validly published genera and nearly 500 validly published species. Despite its widespread use, 16S rRNA gene sequence analysis has proven inadequate for accurately resolving taxonomic relationships within the Roseobacteraceae, resulting in significant inconsistencies in the current classification of this family. Notably, a significant proportion of Roseobacteraceae genera contain only one species, suggesting a potential for over-splitting. To address this issue, we investigated the taxonomic status of three genera, Antarctobacter, Mameliella, and Maliponia, which were originally delineated based on 16S rRNA data. RESULTS: Our phylogenomic analyses, based on single-copy orthologous clusters and a bacterial core gene set, revealed that species from these three genera form a robust and distinct clade. Furthermore, genome-wide similarity indices, including average amino acid identity (AAI), percentage of conserved proteins (POCP), genome-wide average nucleotide identity (gANI), and alignment fraction (AF), consistently indicated a close relatedness among these genera. Analysis of the available phenotypic features also revealed that species of the genera Antarctobacter,Mameliella and Maliponia are very closely related and lack distinct characteristics. CONCLUSIONS: Our findings suggest that Antarctobacter, Mameliella, and Maliponia may represent a single genus. We therefore propose that Mameliella and Maliponia species should be reclassified as members of the genus Antarctobacter. This re-evaluation contributes to the ongoing effort to refine the taxonomy of the Roseobacteraceae, correct historical misclassifications, and reduce the proliferation of underpopulated genera within this ecologically important family. This reclassification provides a more accurate framework for studying the evolution, diversity, and ecological roles of these bacteria, and allows researchers to focus on more significant variations among species. Our results help establish a more reasonable taxonomy within the family Roseobacteraceae.