Genomic Insights into Bifidobacteria

Abstract

SUMMARYSince the discovery in 1899 of bifidobacteria as numerically dominant microbes in the feces of breast-fed infants, there have been numerous studies addressing their role in modulating gut microflora as well as their other potential health benefits. Because of this, they are frequently incorporated into foods as probiotic cultures. An understanding of their full interactions with intestinal microbes and the host is needed to scientifically validate any health benefits they may afford. Recently, the genome sequences of nine strains representing four species ofBifidobacteriumbecame available. A comparative genome analysis of these genomes reveals a likely efficient capacity to adapt to their habitats, withB. longumsubsp.infantisexhibiting more genomic potential to utilize human milk oligosaccharides, consistent with its habitat in the infant gut. Conversely,B. longumsubsp.longumexhibits a higher genomic potential for utilization of plant-derived complex carbohydrates and polyols, consistent with its habitat in an adult gut. An intriguing observation is the loss of much of this genome potential when strains are adapted to pure culture environments, as highlighted by the genomes ofB. animalissubsp.lactisstrains, which exhibit the least potential for a gut habitat and are believed to have evolved from theB. animalisspecies during adaptation to dairy fermentation environments.