produces sulfide to compete with in the gut lumen.

Hydrogen sulfide production is a characteristic that distinguishes serovars from closely related species, such as , but its biological significance remains obscure. Here, we show that PhsABC and AsrABC-mediated hydrogen sulfide production by serovar () Typhimurium was linked to an increased abundance of and inhibition of cytochrome oxidase-mediated aerobic respiration of in the murine large intestine. Functional and operons provided a growth benefit to Typhimurium in the cecum of free conventional mice only upon inoculation with commensal In gnotobiotic mice engrafted with a defined community of 17 human isolates, Typhimurium infection inhibited cytochrome oxidase-mediated aerobic respiration in only in the presence of , a sulfide-producing representative of the A Typhimurium strain deficient for hydrogen sulfide production ( mutant) did not inhibit cytochrome oxidase-mediated aerobic respiration in , even when was present. Collectively, these data suggest that the and operons of serovars provide a benefit during competition with closely related bacteria, such as , by inhibiting cytochrome oxidase-mediated aerobic respiration of the commensal.