标题:Infant-gut associated Bifidobacterium dentium strains utilize the galactose moiety and release lacto- N-triose from the human milk oligosaccharides lacto- N-tetraose and lacto- N-neotetraose
摘要:Much evidence suggests a role for human milk oligosaccharides (HMOs) in establishing the infant microbiota in the large intestine, but the response of particular bacteria to individual HMOs is not well known. Here twelve bacterial strains belonging to the genera
Bifidobacterium,
Enterococcus,
Limosilactobacillus,
Lactobacillus,
Lacticaseibacillus,
Staphylococcus and
Streptococcus were isolated from infant faeces and their growth was analyzed in the presence of the major HMOs, 2′-fucosyllactose (2′FL), 3-fucosyllactose (3FL), 2′,3-difucosyllactose (DFL), lacto-
N-tetraose (LNT) and lacto-
N-
neo-tetraose (LNnT), present in human milk. Only the isolated
Bifidobacterium strains demonstrated the capability to utilize these HMOs as carbon sources.
Bifidobacterium infantis Y538 efficiently consumed all tested HMOs. Contrarily,
Bifidobacterium dentium strains Y510 and Y521 just metabolized LNT and LNnT. Both tetra-saccharides are hydrolyzed into galactose and lacto-
N-triose (LNTII) by
B. dentium. Interestingly, this species consumed only the galactose moiety during growth on LNT or LNnT, and excreted the LNTII moiety. Two β-galactosidases were characterized from
B. dentium Y510, Bdg42A showed the highest activity towards LNT, hydrolyzing it into galactose and LNTII, and Bdg2A towards lactose, degrading efficiently also 6′-galactopyranosyl-
N-acetylglucosamine,
N-acetyl-lactosamine and LNnT. The work presented here supports the hypothesis that HMOs are mainly metabolized by
Bifidobacterium species in the infant gut.