Diet modulates Vibrio cholerae colonization and competitive outcomes with the gut microbiota.

The amount or type of dietary macronutrients dramatically changes the microbiota and physicochemical environment of the gut. Because the microbiota plays key roles in pathogen susceptibility, macronutrients could impact infection outcomes. We show that dietary protein sources differentially restrict colonization of Vibrio cholerae (V. cholerae) as well as impact pathogen-dependent changes in microbiota composition. Specifically, dietary proteins, notably casein, alter levels of the V. cholerae central flagellar regulator, FlrA, which controls expression of the type VI secretion system (T6SS), a key mediator of intra-bacterial competition. Resultant decreases in T6SS lead to a competitive disadvantage for V. cholerae against human commensal Escherichia coli, as well as changes in the abundance and composition of a model human gut microbiota. Mutations in FlrA restore V. cholerae T6SS expression and abrogate diet-dependent impacts on V. cholerae infection. These findings suggest dietary interventions for restricting V. cholerae and highlight the importance of diet in pathogen-commensal interactions.