Three novel Rothia species associated with Antarctic birds harbour novel biosynthetic gene clusters

Antarctica’s unique environment supports diverse avian populations, including penguins, skuas, and gulls. As climate-driven pressures on these populations intensify, their microbiota receives increased attention due to their relevance for host health. In this study, we investigated 11 bacterial isolates associated with Antarctic birds using a polyphasic taxonomic approach integrating genomic and phenotypic data. Phylogenetic analysis of 16S rRNA gene sequences separated the strains into two lineages within the genus Rothia. A core-genome-based phylogenomic tree further resolved one lineage into two clades, resulting in three strain groups distinct from all validly named Rothia species. Genome-relatedness indices confirmed that the three lineages represent novel species within the genus Rothia. Functional genomic analysis, combined with phenotypic testing, revealed broad metabolic capabilities, including versatile carbohydrate and amino acid metabolism. Further genome mining revealed the presence of several biosynthetic gene clusters, potentially encoding terpenes, siderophores, and other bioactive compounds. Some of these clusters likely encode variants of enterobactin, a nonribosomally synthesised siderophore. Together, these findings broaden the known diversity of Rothia by three proposed novel species, Rothia ornithocola sp. nov., Rothia pygoscelis sp. nov., and Rothia antarctica sp. nov., and highlight genomic and phenotypic features that contribute to the ecology of Antarctic avian-associated bacteria.