Mucin Type Drives Composition and Mucin Glycan Degradation of an In Vitro Synthetic Microbial Community

Specific human gut bacteria can degrade and utilise mucin glycans from the intestinal mucus layer. Consequently, these available glycans affect the gut microbiota and vice versa. Therefore, we studied the influence of mucin type on mucosal microbiota composition and mucin glycan degradation using an in vitro synthetic community consisting of mucin glycan degraders and cross-feeders commonly residing in the human colonic mucus layer. This community was incubated with different mucin substrates resulting in unique microbial community compositions, glycan degradation patterns, and metabolite production profiles for each condition. Porcine gastric mucin O-glycans were completely degraded by a diverse community with high relative abundance of Akkermansia muciniphila, Ruminococcus gnavus, Ruminococcus torques, and Faecalibacterium duncaniae. Presence of porcine gastric mucin and bovine submaxillary glands mucin resulted in A. muciniphila dominating the community. Availability of sialylated structures resulted in an increased relative abundance of A. muciniphila and Bacteroides fragilis, but Ruminococcus spp. decreased in relative abundance. This indicates that available sialic acid considerably influences community composition and function. Furthermore, glycan degradation and metabolite production were also affected by mucin type. This novel approach clearly demonstrated the interaction between mucin type and the microbiota composition and shows new insights in how these affect each other.