To confirm that FruI and FruT influence the virulence of V. cholerae by regulating the intracellular cAMP level in the small intestine of mice, we performed competitive infection assays in mice between a mutant in the adenylate cyclase gene cyaA (ΔcyaA) and the double mutants ΔfruIΔcyaA and ΔfruTΔcyaA, respectively. The gene discussed is ADCY1; the disease is infection.