Functions of VPA1418 and VPA0305 Catalase Genes in Growth of Vibrio parahaemolyticus under Oxidative Stress

Abstract

ABSTRACT The marine foodborne enteropathogen Vibrio parahaemolyticus has four putative catalase genes. The functions of two katE -homologous genes, katE1 (VPA1418) and katE2 (VPA0305), in the growth of this bacterium were examined using gene deletion mutants with or without complementary genes. The growth of the mutant strains in static or shaken cultures in a rich medium at 37°C or at low temperatures (12 and 4°C), with or without competition from Escherichia coli , did not differ from that of the parent strain. When 175 μM extrinsic H 2 O 2 was added to the culture medium, bacterial growth of the Δ katE1 strain was delayed and growth of the Δ katE1 Δ katE2 and Δ katE1 Δ ahpC1 double mutant strains was completely inhibited at 37°C for 8 h. The sensitivity of the Δ katE1 strain to the inhibition of growth by H 2 O 2 was higher at low incubation temperatures (12 and 22°C) than at 37°C. The determined gene expression of these catalase and ahpC genes revealed that katE1 was highly expressed in the wild-type strain at 22°C under H 2 O 2 stress, while the katE2 and ahpC genes may play an alternate or compensatory role in the Δ katE1 strain. This study demonstrated that katE1 encodes the chief functional catalase for detoxifying extrinsic H 2 O 2 during logarithmic growth and that the function of these genes was influenced by incubation temperature.