Bosom Buddies: The Symbiotic Relationship Between Infants and Bifidobacterium longum ssp. longum and ssp. infantis. Genetic and Probiotic Features.

The intestinal microbiota is a complex community that plays an important role in human health from the initial steps of its establishment. Its microbial composition has been suggested to result from selective pressures imposed by the host and is modulated by competition among its members. Bifidobacterium longum is one of the most abundant species of the Bifidobacterium genus in the gut microbiota of healthy breast-fed infants and adults. The recent advancements of 'omics techniques have facilitated the genetic and functional studies of different gut microbiota members. They have revealed the complex genetic pathways used to metabolize different compounds that likely contribute to the competitiveness and persistence of B. longum in the colon. The discovery of a genomic island in B. longum ssp. infantis that encodes specific enzymes for the metabolism of human milk oligosaccharides suggests a specific ecological adaptation. Moreover, B. longum is widely used as probiotic, and beneficial effects in infant health have been reported in several studies.