Trillions of bacteria live in homeostasis with the host immune system within the gastrointestinal tract. A primary function of the normal microbiota is to protect the host from enteric pathogens; however, little is known about the mechanisms by which this protection occurs. To study this mechanism, we utilize a model in which the commensal bacterium, Bacillus subtilis, protects mice from disease induced by the pathogen Citrobacter rodentium. The pathogenesis of C. rodentium is similar to the human pathogens enteropathogenic and enterohemorrhagic E. coli. Previous work in our lab has demonstrated that exopolysaccharides produced by B. subtilis mediate protection. My project examines the intracellular mechanisms through which B. subtilis exopolysaccharides inhibit C. rodentium induced inflammation.