Metabolism of four α-glycosidic linkage-containing oligosaccharides by Bifidobacterium breve UCC2003.

Members of the genus Bifidobacterium are common inhabitants of the gastrointestinal tract of humans and other mammals, where they ferment many diet-derived carbohydrates that cannot be digested by their host. To extend our understanding of bifidobacterial carbohydrate utilisation, we investigated the molecular mechanisms by which eleven strains of Bifidobacterium breve metabolize four distinct α-glucose and/or α-galactose-containing oligosaccharides, namely raffinose, stachyose, melibiose and melezitose. Here we demonstrate that all B. breve strains examined possess the ability to utilise raffinose, stachyose and melibiose. However, the ability to metabolize melezitose was not ubiquitous for all tested B. breve strains. Transcriptomic and functional genomic approaches identified a gene cluster dedicated to the metabolism of α-galactose-containing carbohydrates, while an adjacent gene cluster, dedicated to the metabolism of α-glucose-containing melezitose, was identified in strains able to use this carbohydrate.