Roles of Alkyl Hydroperoxide Reductase Subunit C (AhpC) in Viable but Nonculturable Vibrio parahaemolyticus

Abstract

ABSTRACTAlkyl hydroperoxide reductase subunit C (AhpC) is the catalytic subunit responsible for the detoxification of reactive oxygen species that form in bacterial cells or are derived from the host; thus, AhpC facilitates the survival of pathogenic bacteria under environmental stresses or during infection. This study investigates the role of AhpC in the induction and maintenance of a viable but nonculturable (VBNC) state inVibrio parahaemolyticus. In this investigation,ahpC1(VPA1683) andahpC2(VP0580) were identified in chromosomes II and I of this pathogen, respectively. Mutants with deletions of these twoahpCgenes and their complementary strains were constructed from the parent strain KX-V231. The growth of these strains was monitored on tryptic soy agar–3% NaCl in the presence of the extrinsic peroxides H2O2andtert-butyl hydroperoxide (t-BOOH) at different incubation temperatures. The results revealed that bothahpCgenes were protective againstt-BOOH, whileahpC1was protective against H2O2. The protective function ofahpC2at 4°C was higher than that ofahpC1. The times required to induce the VBNC state (4.7 weeks) at 4°C in a modified Morita mineral salt solution with 0.5% NaCl and then to maintain the VBNC state (4.7 weeks) in anahpC2mutant and anahpC1 ahpC2double mutant were significantly shorter than those for the parent strain (for induction, 6.2 weeks; for maintenance, 7.8 weeks) and theahpC1mutant (for induction, 6.0 weeks; for maintenance, 8.0 weeks) (P< 0.03). Complementation with anahpC2gene reversed the effects of theahpC2mutation in shortening the times for induction and maintenance of the VBNC state. This investigation identified the different functions of the twoahpCgenes and confirmed the particular role ofahpC2in the VBNC state ofV. parahaemolyticus.