Abstract
Bifidobacteria are associated with a host of health benefits and are typically dominant in the gut microbiota of healthy, breast-fed infants. A key adaptation, facilitating the establishment of these species, is their ability to consume particular sugars, known as human milk oligosaccharides (HMO), which are abundantly found in breastmilk. In the current study, we aimed to characterise the co-operative metabolism of four commercial infant-derived bifidobacteria (Bifidobacterium bifidum R0071, Bifidobacterium breve M-16V, Bifidobacterium infantis R0033, and Bifidobacterium infantis M-63) when grown on HMO. Three different HMO substrates (2′-fucosyllactose alone and oligosaccharides isolated from human milk representing non-secretor and secretor status) were employed. The four-strain combination resulted in increased bifidobacterial numbers (> 21%) in comparison to single strain cultivation. The relative abundance of B. breve increased by > 30% during co-cultivation with the other strains despite demonstrating limited ability to assimilate HMO in mono-culture. HPLC analysis revealed strain-level variations in HMO consumption. Metabolomics confirmed the production of formate, acetate, 1,2-propanediol, and lactate with an overall increase in such metabolites during co-cultivation. These results support the concept of positive co-operation between multiple bifidobacterial strains during HMO utilisation which may result in higher cell numbers and a potentially healthier balance of metabolites.
Highlights
Establishment of the infant gut microflora is a highly complex process, with feeding regime profoundly impacting on the development of neonate’s microbial gut e cology[1–3]
Rosell®-71 (R0071), Bifidobacterium infantis Rosell®-33 (R0033), Bifidobacterium breve M-16V, and Bifidobacterium infantis M-63 cultivated in mono-culture on human milk oligosaccharides (HMO)-supplemented media were evaluated and compared to the growth profiles of the strains when grown in a four strain co-culture on the same carbohydrate sources (Fig. 1a,b,c)
The most abundant α1,2-fucosylated HMO was eliminated from the powder, the preparation contained other H-antigen containing HMOs such as difucosyllactose (DFL), lacto-N-fucopentaose I (LNFP I), and lacto-N-difucohexaose I (LNDFH I) (Supplementary Fig. S1)
Summary
Establishment of the infant gut microflora is a highly complex process, with feeding regime profoundly impacting on the development of neonate’s microbial gut e cology[1–3]. Variability in the chemical and structural conformations of HMO is biologically relevant[7] These glycans serve as selective regulators of infant gut microbiota composition, and facilitate the development of a Bifidobacterium-dominant microbiota in breast-fed infants[8,9]. Many members of the genus Bifidobacterium are known to dedicate a relatively large proportion of their genome to carbohydrate utilization, reflecting their adaptation to metabolism of hostproduced and/or host-ingested/dietary carbohydrates Some of these genomes, infant bifidobacterial species, display a clear adaptation to the nursing period when the diet of their host may be solely composed of (HMO-rich) breast milk[14–16]. In vitro growth experiments have revealed species-dependent utilization of individual HMO among Bifidobacterium[17,18] These studies have enabled detailed profiling of (bifido)bacterial consumption of individual HMO and demonstrate specific and preferential oligosaccharide consumption by particular bifidobacterial strains[19–21]. Unravelling HMO assimilation phenotypes and understanding the oligosaccharide structural complexity required to enrich specific beneficial bacterial communities allows for the development of targeted and personalised HMO-containing probiotic products with well-defined microbial, metabolic, and infant health outcomes
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