Bifidobacteria: Ecology and Coevolution With the Host

Bacteria reside in a myriad of ecological niches. The human gut is among the most densely populated habitats, where a plethora of microorganisms are believed to have coevolved to beneficially influence the health status of their human host. This chapter reviews the current status regarding the ecology of bifidobacteria, as well as their genetic adaptation to the mammalian gut. In this context, it is pertinent to discuss their complex arsenal of carbohydrate active enzymes directed toward the metabolism of host-glycans and plant-carbohydrates. In silico analyses of metagenomic datasets corresponding to both infant and adult subjects highlight the functional contribution of bifidobacteria in terms of expanding the overall human gut glycobiome. Finally, we discuss the available support for the hypothesis of saccharide resource-sharing among bifidobacteria through species-specific metabolic specialization and cross-feeding activities, which forges trophic relationships between members of the gut microbiota.