Citrobacter FR/FF strain dropout. Diet-driven differential response of Akkermansia muciniphila modulates pathogen susceptibility

The diminished gut mucus layer caused by a microbiota lacking dietary fiber is thought to explain the increased vulnerability to Citrobacter rodentium, a pathogen known for its attaching and effacing behavior (Desai et al., 2016). Nevertheless, it is still unclear whether and how specific mucin-degrading bacteria contribute to this phenomenon. We aimed to determine which specific bacteria or functions play a role in the increased susceptibility to tC. rodentium infection under fiber deprivation. To this end, we utilized a 14-member synthetic human gut microbiota (14SM) in gnotobiotic mice and selectively removed specific mucin-degrading bacteria. Through a strain dropout approach to enact targeted changes of the presence of functionally relevant gut microbiota, we demonstrate that an enrichment of the mucus-specialist bacterium A. muciniphila heightens susceptibility to infection in conditions of fiber deprivation. The ability to resist infection can be conferred either by providing a diet rich in fiber or by eliminating A. muciniphila. This microbe appears to play a direct or indirect role in the excessive erosion of the gut mucus layer and behavioral changes of other members within the gut microbial community.