<i>Ruminococcus gnavus</i> , a member of the human gut microbiome associated with Crohn’s disease, produces an inflammatory polysaccharide

TLDR

Gut bacteria regulate metabolism, immunity, and pathogen defense, and dysbiosis has been linked to inflammatory bowel diseases such as Crohn’s disease. We identified an inflammatory polysaccharide from *Ruminococcus gnavus* that stimulates TNFα production by dendritic cells, providing a plausible molecular link between this bacterium and Crohn’s disease flares.

Abstract

Significance The bacteria that live within the human gut play crucial roles in regulating our primary metabolism, protecting us from pathogens, and developing our immune system. Imbalances in bacterial community structure have been implicated in many diseases, such as Crohn’s disease, an inflammatory bowel disease. We found and characterized an inflammatory polysaccharide produced by the gut bacterium Ruminococcus gnavus , populations of which bloom during flares of symptoms in patients with Crohn’s disease. This molecule induces the production of inflammatory cytokines like TNFα by dendritic cells and may contribute to the association between R. gnavus and Crohn’s disease. This work establishes a plausible molecular mechanism that may explain the association between a member of the gut microbiome and an inflammatory disease.