Sublethal heat stress of Vibrio parahaemolyticus

Abstract

When Vibrio parahaemolyticus ATCC 17802 was heated at 41°C for 30 min in 100 mM phosphate 3% NaCl buffer (pH 7.0), the plate counts obtained when using Trypticase soy agar containing 0.25% added NaCl (0.25 TSAS) were nearly 99.9% higher than plate counts using Trypticase soy agar containing 5.5% added NaCl (5.5 TSAS). A similar result was obtained when cells of V. parahaemolyticus were grown in a glucose salt medium (GSM) and heated at 45°C. The injured cells recovered salt tolerance within 3 h when placed in either 2.5 TSBS or GSM at 30°C. The addition of chloramphenicol, actinomycin D, or nalidixic acid to 2.5 TSBS during recovery of cells grown in 2.5 TSBS indicated that recovery was dependent upon protein, ribonucleic acid (RNA), and deoxyribonucleic acid (DNA) synthesis. Penicillin did not inhibit the recovery process. Heat injured, GSM grown cells required RNA synthesis but not DNA synthesis during recovery in GSM. Chemical analyses showed that total cellular RNA decreased and total cellular DNA remained constant during heat injury. The addition of [6 3H]uracil, L [U 14C]leucine, and [methyl 3H]thymidine to the recovery media confirmed the results of the antibiotic experiments.