Fucosylated Human Milk Oligosaccharides Drive Structure‐Specific Syntrophy between Bifidobacterium infantis and Eubacterium hallii within a Modeled Infant Gut Microbiome

Abstract

Scope: Fucosylated human milk oligosaccharides (fHMOs) are metabolized by Bifidobacterium infantis and promote syntrophic interactions between microbiota that colonize the infant gut. The role of fHMO structure on syntrophic interactions and net microbiome function is not yet fully understood. Methods and results: Metabolite production and microbial populations are tracked during mono-and co-culture fermentations of 2ʹfucosyllactose (2ʹFL) and difucosyllactose (DFL) by two B. infantis strains and Eubacterium hallii. This is also conducted in an in vitro modeled microbiome supplemented by B. infantis and/or E. hallii. Metabolites are quantified by high performance liquid chromatography. Total B. infantis and E. hallii populations are quantified through qRT-PCR and community composition through 16S amplicon sequencing. Differential metabolism of 2ʹFL and DFL by B. infantis strains gives rise to strain-and fHMO structure-specific syntrophy with E. hallii. Within the modeled microbial community, fHMO structure does not strongly alter metabolite production in aggregate, potentially due to functional redundancy within the modeled community. In contrast, community composition is dependent on fHMO structure. Conclusion: Whereas short chain fatty acid production is not significantly altered by the specific fHMO structure introduced to the modeled community, specific fHMO structure influences the composition of the gut microbiome.

Daily skin-to-skin contact alters microbiota development in healthy full-term infants

“…Anaerobutyricum soehngenii can produce butyrate by utilizing the byproducts of other early colonizers that metabolize human milk oligosaccharides. 83 , 84 It has been positively associated with infant colic 85 and is under investigation for its benefits in relation to glucose metabolism. 86 …”

2-Fucosyllactose Metabolism by Bifidobacteria Promotes Lactobacilli Growth in Co-Culture

“…Classical HMO consumers B. bifidum and B. infantis are often detected in low numbers in the feces of breast-fed infants, while B. longum and B. breve are regularly found as the dominant species in infant stools, even though they demonstrate minimal growth in HMO in vitro [8,13,18,43]. In spite of that, these types of associations may bring some benefit for 2 FL-degrading bifidobacteria, such as the abovementioned upregulation of bifidobacterial carbohydrate transporters [42,44], or syntrophic interactions based on the end-products of HMO metabolism such as 1,2-propanediol, and acetic and lactic acid metabolized to propionate or butyrate by other gut members [20]. More investigation is needed about the interaction between 2 FL-degrading bifidobacteria and other members of the gut microbiota, and how the ability to degrade this and other HMO could influence the microbiota establishment in neonates and the evolution of the microbiota in adult life.…”

“…Besides the cross-feeding between bifidobacteria, synergistic interactions between 2 FL-consuming bifidobacteria and other gut microorganisms such as Faecalibacterium prausnitzii [19] or Anaerobutyricum hallii [20,21] have also been reported. In spite of this, the knowledge on synergistic mechanisms among bifidobacteria degrading 2 FL and other important commensal members of the intestinal microbiota of infants is still scarce.…”

Transmission and Persistence of Infant Gut-Associated Bifidobacteria

“…These organic acids lower the infant's gut pH and protect against pathogen colonization [21]. The ratio of lactate to acetate is an indicator of metabolic efficiency for bifidobacterial cellular operations, and once secreted, they are responsible for initiating a downstream cascade of syntrophic interactions [20,22]. In addition, B. infantis colonization normalizes intestinal barrier function in a mouse model of colitis and potentially in human infants [23].…”