Fatty acid composition, cell morphology and responses to challenge by organic acid and sodium chloride of heat-shocked Vibrio parahaemolyticus

Vibrio parahaemolyticus 690, a clinical strain, was subjected to heat shock at 42 degrees C for 45 min. The fatty acid profile and recovery of the heat-shocked cells of V parahaemolyticus on TSA-3.0% NaCl, APS agar (Alkaline peptone salt broth supplemented with 1.5% agar) and TCBS (Thiosulfate-citrate-bile salts-sucrose agar) were compared with those of the nonbeat-shocked cells. Furthermore, the morphology of V parahaemolyticus and survival in the presence of various organic acids (25 mM acetic acid, lactic acid, citric acid or tartaric acid) and NaCl (0.1% and 20.0%) as influenced by heat shock treatment were also investigated. It was found that heat shock caused a change in the proportions of the unsaturated and saturated fatty acid. The ratio of saturated fatty acids to unsaturated fatty acids observed on beat-shocked V.parahaemolyticus cells was significantly (p < 0.05) higher than that on the control cells. Extensive cell-wall pitting and cell disruption, representing cell-surface damage, were also observed on the cells which were subjected to heat shock treatment. Recovery of beat-shocked cells of V.parahaemolyticus was significantly less on TCBS and APS agar than on TSA-3.0% NaCl. Heat shock decreased the tolerance of V parahaemolyticus to organic acids. The extent of decreased acid tolerance observed on heat-shocked cells varied with the organic acid tested. While heat shock increased the survival of V.parahaemolyticus in the presence of 0.1% NaCl and made the test organism more susceptible to 20.0% NaCl than the control cells. (c) 2005 Elsevier B.V. All rights reserved.