Glycomic and genetic characterization of the metabolism of human milk oligosaccharides by Bifidobacterium species

The molecular basis by which human breast milk supports the development of a protective intestinal microbiome in infants is unknown. Human milk contains over 200 oligosaccharides differing in their mass, charge, sequence and relative abundance. Human milk oligosaccharides (HMO) are quantitatively the third largest and the most diverse component of breast milk. Understanding the molecular details of HMO metabolism by gut microorganisms is important for elucidating their role in modulating infant health and disease. HPLC-Chip TOF MS and MALDI-FTICR MS analytical methods established the role of HMOs as a substrate for the selective growth of bifidobacteria. Among several bifidobacteria tested, B. longum subsp. infantis strains possessed the highest metabolic capacity to consume HMOs. A genome-wide comparative analysis of twelve HMO+/+/-/- B. longum strains demonstrated that all B. longum subsp. infantis strains preserved the metabolic capacity towards utilization of milk-borne nutrients and adaptation to constituents of the infant gastrointestinal tract. Conservation of this genome architecture across several subsp. infantis strains strongly suggests a specific adaptation of this subspecies towards utilization of milk components and colonization of the breast fed infant distal gut.