Bifidobacterium longum subspecies infantis: champion colonizer of the infant gut

Abstract

Oligosaccharides are abundant in human milk. Production of these highly diverse structures requires significant energy expenditure by the mother and yet these human milk oligosaccharides offer no direct nutritive value to her infant. A primary function of human milk oligosaccharides is to shape the infant’s intestinal microbiota with life-long consequences. Bifidobacterium longum subspecies infantis (B. infantis) is unique among gut bacteria in its prodigious capacity to digest and consume any human milk oligosaccharide structure, the result of a large repertoire of bacterial genes encoding an array of glycosidases and oligosaccharide transporters not found in other bacterial species. In vitro, B. infantis grows better than other bacterial strains in the presence of human milk oligosaccharides, displays anti-inflammatory activity in premature intestinal cells, and decreases intestinal permeability. In premature infants, B. infantis given in combination with human milk increases B. infantis and decreases Enterobacteriaceae in the feces. Probiotics containing B. infantis decrease the risk of necrotizing enterocolitis in premature infants. Colonization with B. infantis is also associated with increased vaccine responses. Probiotic organisms have historically been selected based on ease of production and stability. The advantages of B. infantis, selected through coevolution with human milk glycans, present an opportunity for focused manipulation of the infant intestinal microbiota.

Cross-feeding interactions of gut symbionts driven by human milk oligosaccharidesand mucins

“…We showed that Bifidobacterium infantis effectively degraded the full range of the low molecular weight HMOS structures including neutral trioses, tetraoses, and pentaoses as well as acidic trioses. This is consistent with the unique HMOS utilisation capability of Bifidobacterium infantis by encoding a 43kb gene cluster that carries the genes for different oligosaccharides transport proteins and glycosyl hydrolases (Underwood et al 2014). No signal peptide or transmembrane domain was predicted for Bifidobacterium infantis enzymes involved in the cleavage of the monitored HMOS structures (Table S2), indicating intracellular degradation of these substrates.…”

“…Despite the structural similarity between mucins and HMOS ( Fig. 1), only some Bifidobacterium species, particularly Bifidobacterium bifidum strains can utilise mucins for growth (Marcobal et al 2013, Underwood et al 2014.…”

Expert consensus document: The International Scientific Association for Probiotics and Prebiotics (ISAPP) consensus statement on the definition and scope of prebiotics

“…Although 2ʹFL is utilized by B. infantis as well as some strains of B. longum subsp. longum and B. breve 46,47 , the ecological context (that is, infants versus adults) might dictate whether these HMOs are indeed pre biotic. Moreover, having structural equivalence to specific HMOs does not infer functional equiva lence to the con stellation of HMOs in milk 48 .…”

Prenatal and postnatal administration of prebiotics and probiotics

“…A single subspecies, Bifidobacterium longum subsp. infantis has evolved the capacity to transport and consume all the various HMO structures, providing it with a significant advantage in colonization over other gut microbes [45]. It is likely that the prebiotic HMOs, which are produced at significant cost to the mother, play a significant role in many of the observed beneficial effects of human milk.…”