Inter-individual differences determine the outcome of wheat bran colonization by the human gut microbiome.

Gut microbiota research reveals a vital role for the luminal and mucosal gut microbiota in human health. Fewer studies, however, have characterized the microbiome associated with undigested, insoluble dietary particles in the gut. These particles can act as a food source for bacteria and offer a physical platform to which they can attach. In this study, the microbiome colonizing wheat bran particles was analyzed. In a batch experiment, wheat bran particles were separately incubated with the faecal microbiota derived from 10 donors and washed after 48 h to remove loosely attached bacteria. The response of the luminal community to wheat bran and inulin, acting as a well-characterized control, was largely donor-dependent, both functionally, and with respect to the microbiome composition. Depending on the donor, wheat bran and inulin fermentation yielded proportionally higher propionate or butyrate production. Clostridium cluster XIVa and, depending on the donor, Prevotella, Roseburia, Megamonas, Bifidobacterium and Bacteroides species were enriched on the wheat bran particles. These genera include species with the documented ability to serve as primary degraders of wheat bran components and other species depending on cross-feeding to obtain their energy. Both functional groups were present in all donors, despite the large inter-individual differences.