Induction of a viable but nonculturable state in Vibrio parahaemolyticus by a high concentration of salt and its impact on fatty acid composition profile and membrane potential

The study aimed to investigate the effects of a high concentration of salt on the induction of a viable but nonculturable (VBNC) state in V . parahaemolyticus and its impact on fatty acid (FA) composition profile and membrane potential during the persistence of a VBNC state. When three V . parahaemolyticus strains were incubated in artificial sew water (ASW) microcosms containing maximally 30% salt at 4 ºC, these bacteria became uncultivable within 50∼70 d. On day 100, the viable numbers of V . parahaemolyticus that maintained its membrane integrity were 6.0 log CFU/slide in ASW microcosms stored at 4 ºC, implying that a high concentration of salt can be an inducer causing the phase transition of a VBNC state in V . parahaemolyticus . Especially, there was a strong correlation between increased saturated FA proportion and decreased membrane potential (as determined by using N -phenyl- 1 -napthylamine and propidium iodide probes) during the persistence of a VBNC state in V . parahaemolyticus , indicating that VBNC cells had increasingly permeable membrane properties. Knowledge on the characteristics of VBNC cells may provide better understanding of the ecology of bacteria, as well as their survival mechanisms. • VBNC induction of V. parahaemolyticus was accelerated by NaCl addition. • Cytotoxicity was reduced however remained in the VBNC states. • Changes in morphology and membrane permeability were observed in the VBNC states. • VBNC induction was accompanied by changes in selected cellular properties.