Salmonella Typhimurium uses anaerobic respiration to overcome propionate-mediated colonization resistance

The gut microbiota benefits the host by limiting enteric pathogen expansion (colonization resistance) partially via the production of inhibitory metabolites. Propionate, a short-chain fatty acid produced by microbiota members, is proposed to mediate colonization resistance against Salmonella enterica serovar Typhimurium ( S. Tm). Here, we show that S. Tm overcomes the inhibitory effects of propionate by using it as a carbon source for anaerobic respiration. We determined that propionate metabolism provides an inflammation-dependent colonization advantage to S. Tm during infection. Such benefit was abolished in the intestinal lumen of Salmonella -infected germ-free mice. Interestingly, S. Tm propionate-mediated intestinal expansion was restored when germ-free mice were monocolonized with Bacteroides thetaiotaomicron (B. theta), a prominent propionate producer in the gut, but not when mice were monocolonized with a propionate production-deficient B. theta strain. Taken together, our results reveal a novel strategy used by S. Tm to mitigate colonization resistance by metabolizing microbiota-derived propionate. ### Competing Interest Statement The authors have declared no competing interest.