Protective roles of katG-homologous genes against extrinsic peroxides in Vibrio parahaemolyticus.

The marine foodborne enteropathogen, Vibrio parahaemolyticus , has four putative catalase genes. Function of the katG -homologous genes, katG1 (VPA0768) and katG2 (VPA0453), was examined using gene deletion mutants, and compared with those of the katE -homologous genes, katE1 (VPA1418) and katE2 (VPA0305). Bacterial growth of ΔkatG1 was significantly delayed in the presence of 200–300 μM H2O2, and such inhibition was enhanced when incubation temperature was lowered from 37°C to 22°C. In the stationary phase, the ΔkatG1 strain was more susceptible to the lethal dosage of H2O2 than the ΔkatE1 strain. The minimum inhibitory concentrations and minimum bactericidal concentrations revealed that ΔkatE1/ΔkatE2 strains were more susceptible to H2O2 than the ΔkatG1/ΔkatG2 strains in exponential phase, while ΔkatG1 was more susceptible than the ΔkatE1/ΔkatE2 strains in the starved culture. This study demonstrated the chief antioxidative role of katG1 in the stationary phase and starved culture of V. parahaemolyticus , while katG1 and katG2 were also responsive to H2O2 and cumene hydroperoxide in the exponential phase.