Maryse Berkhout (Wageningen University & Research)

Summary of presentation:
Human milk contains oligosaccharides (HMOs) which reach the infant gut where they are selectively digested by the gut microbiota. To mimic this prebiotic effect, glycans such as short-chain galacto- and long-chain fructooligosaccharides (scGOS/lcFOS; 9:1), or selected individual HMOs can be added to infant formula. Due to structural differences between scGOS/lcFOS and HMOs, they may have distinct effects on the infant gut microbiota. Therefore, we studied how different mixes of early life dietary glycans affected community composition and function in an infant gut synthetic community.

We used our previously characterised 13-member synthetic microbial community with common strains of the healthy breastfed infant gut to study the effect of different substrates. The conditions were Lac (lactose only), Lac_GF (lactose and scGOS/lcFOS), Lac_GF_2FL (lactose, scGOS/lcFOS and 2’-fucosyllactose), Lac_5HMO (lactose and 5HMO mix (2’-fucosyllactose, 3-fucosyllactose, 3’-sialyllactose, 6’-sialyllactose and lacto-N-tetraose), Lac_5HMO_GF (lactose, 5HMO mix and scGOS/lcFOS), and tHMO (total HMO extract from pooled human milk including lactose). We incubated the community with these substrates and tracked species-level relative abundance, absolute abundance, metabolite production and substrate degradation. Using metaproteomics, we inferred community function.

In all conditions containing complex sugars, Bifidobacterium was the dominant genus. However, when the 5HMO mix was present, Bifidobacterium bifidum was the predominant species; in conditions Lac_GF and Lac_GF_2FL, Bifidobacterium infantis and Bifidobacterium breve dominated. Interestingly, the composition of the community in 5HMO mix-containing conditions resembled the composition of the community grown on tHMO. Through metaproteomics, we discovered that most glycoside hydrolases (GHs) were produced by Bifidobacterium spp., including all detected fucosidases and sialidases, and most galactosidases, glucosidases and hexosaminidases. Furthermore, there were differences in metabolite concentration and substrate degradation.

A more diverse mix of HMOs stimulates the development of a community that is more like the same microbial community grown on a total HMO extract compared to supplementation of only 2’-fucosyllactose.