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 nonheat-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 heat-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 heat-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.
Graduate Institute of Food Science and Technology, National Taiwan University 59, lane 144, Keelung Rd., Sec. 4, Taipei, Taiwan.
Ming-Lun
ML
Chiang
Roch-Chui
RC
Yu
Cheng-Chun
CC
Chou
D000143:Acids / Q000494:pharmacology*; D015169:Colony Count, Microbial; D004305:Dose-Response Relationship, Drug; D005227:Fatty Acids / Q000032:analysis*; D005231:Fatty Acids, Unsaturated / Q000032:analysis; D005506:Food Contamination / Q000032:analysis / Q000517:prevention & control; D005516:Food Microbiology; D006358:Hot Temperature; D008854:Microscopy, Electron; D012965:Sodium Chloride / Q000494:pharmacology*; D014736:Vibrio parahaemolyticus / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism / Q000648:ultrastructure
D000143:Acids; D005227:Fatty Acids; D005231:Fatty Acids, Unsaturated; D012965:Sodium Chloride