Unveiling Genomic Diversity among Members of the Species , a Widely Distributed Gut Commensal of the Animal Kingdom.

Bifidobacteria are commensals of the animal gut and are commonly found in mammals, birds, and social insects. Specifically, strains of , , , and are widely distributed in the mammalian gut. In this context, we investigated the genetic variability and metabolic abilities of the taxon, whose genomic characterization has so far not received much attention. Phylogenomic analysis of the genome sequences of 60 strains revealed that subsp. and subsp. may actually represent two distinct bifidobacterial species. Furthermore, our analysis highlighted metabolic differences between members of these two subspecies. Moreover, comparative analyses of genetic strategies to prevent invasion of foreign DNA revealed that the subsp. group exhibits greater genome plasticity. In fact, the obtained findings indicate that subsp. is more adaptable to different ecological niches such as the mammalian and avian gut than is subsp. Currently, little information exists on the genetics of the taxon due to the limited number of sequenced genomes belonging to this species. In order to survey genome variability within this species and explore how members of this taxon evolved as commensals of the animal gut, we isolated and decoded the genomes of 51 newly isolated strains. Comparative genomics coupled with growth profiles on different carbohydrates has further provided insights concerning the genotype and phenotype of members of the taxon.