Evolutionary architecture of the infant-adapted group of Bifidobacterium species associated with the probiotic function.

Bifidobacteria, often associated with the gastrointestinal tract of animals, are well known for their roles as probiotics. Among the dozens of Bifidobacterium species, Bifidobacterium bifidum, B. breve, and B. longum are the ones most frequently isolated from the feces of infants and known to help the digestion of human milk oligosaccharides. To investigate the correlation between the metabolic properties of bifidobacteria and their phylogeny, we performed a phylogenomic analysis based on 452 core genes of forty-four completely sequenced Bifidobacterium species. Results show that a major evolutionary event leading to the clade of the infant-adapted species is linked to carbohydrate metabolism, but it is not the only factor responsible for the adaptation of bifidobacteria to the gut. The genome of B. longum subsp. infantis, a typical bifidobacterium in the gut of breast-fed infants, encodes proteins associated with several kinds of species-specific metabolic pathways, including urea metabolism and biosynthesis of riboflavin and lantibiotics. Our results demonstrate that these metabolic features, which are associated with the probiotic function of bifidobacteria, are species-specific and highly correlate with their phylogeny.

Complete genome sequence of the probiotic bacterium Bifidobacterium breve KCTC 12201BP isolated from a healthy infant.

We present the completely sequenced genome of Bifidobacterium breve CBT BR3, which was isolated from the feces of a healthy infant. The 2.43-Mb genome contains several kinds of genetic factors associated with health promotion of the human host such as oligosaccharide-degrading genes and vitamin-biosynthetic genes.