Effects of Heat Shock on the Thermotolerance, Protein Composition, and Toxin Production of Vibrio parahaemolyticus

Abstract

Vibrio parahaemolyticus, an important seafood-associated enteropathogen, usually encounters different adverse conditions in its native or food-processing environment, and the stresses resulting from these conditions may affect the survival of this pathogen and thus change its risk with regard to food hygiene. In this study, we investigated the thermotolerance of V. parahaemolyticus under sublethal heat shock and characterized this response by examining the changes in protein profiles and toxin production. Logarithmically grown cells heat shocked at 42 degrees C for 30 min were more resistant to thermal inactivation at 47 degrees C than were unshocked cells. After the 25 degrees C culture was heat shocked, 24 species of proteins were induced, while 13 species were inhibited, as indicated by polyacrylamide gel electrophoresis. DnaJ-, GroEL-, and GroES-like proteins with molecular sizes of 47, 62, and 12 kDa, respectively, were detected by immunoblotting with antibodies raised against the Escherichia coli proteins. During 1 to 8 h of heat shock, GroEL-like protein was produced in substantial amounts and was present in the periplasmic and extracellular fractions, while DnaJ- and GroES-like proteins were present mainly in the total cellular fraction. DnaK-like protein was not detected; nevertheless, the presence of the dnaK-like genetic element was revealed by Southern blotting. Production of thermostable direct hemolysin, the major virulence factor in V. parahaemolyticus, was enhanced in the cells heat shocked at 42 degrees C but not in those heat shocked at 37 degrees C.

Effects of sublethal heat, bile and organic acid treatments on the tolerance of Vibrio parahaemolyticus to lethal low-salinity

“…For the preparation of acid-adapted cultures, bacterial cells were harvested and resuspended in equal volumes of PBS with 3.0% NaCl and 20 amino acids (AA-PBS-3.0% NaCl, alanine, arginine,asparagine, aspartic acid, cysteine, glutamine, glutamic acid, glycine, histidine, isoleucine, leucine, lysine, methionine, penylalanine, praline, serine, threonine, tryptophan, tyrosine and valine, all at 20 mg/l) (Wong et al, 2002) which had been acidified to pH 4.48 using 1 N HCl and incubated at 25 C for 20 min (Wong et al, 1998). In the preparation of heat-adapted cultures, bacterial cells were harvested and resuspended in AA-PBS-3.0% NaCl that had been preheated to 41 C for 20 min (Wong et al, 2002).…”

“…V. parahaemolyticus encounters various stresses in its natural habitat, during food processing or in a human host, while the stress adaptation and cross-protection has been characterized in this pathogen (Wong et al, 2002;Yeung & Boor, 2004). Under carbon starvation, V. parahaemolyticus exhibits cross-protection against heat, hypoosmotic (13 mM NaCl) and oxidative stresses (Koga & Takumi, 1995b), and also protects against freeze-thawing treatment (Wong, Chang, & Chen, 2004).…”

Evaluation of Typing of Vibrio parahaemolyticus by Three PCR Methods Using Specific Primers

“…Forty strains of V. parahaemolyticus isolated from outbreaks in Taiwan during 1993 and 1994 and representing different PFGE patterns were analyzed here (28). Clinical strain ST550, O4:K13 and Kanagawa phenomenon positive and originating from Japan, was used as a reference strain (34). Escherichia coli JM109, V. cholerae 569B, and V. vulnificus CCRC12905 were used as interspecies reference strains.…”

Analysis of the Envelope Proteins of Heat‐Shocked Vibrio parahaemolyticus Cells by Immunoblotting and Biotin‐Labeling Methods

“…Protein samples were separated by electrophoresis, transferred onto nitrocellulose membrane, and detected by antiserum raised against the heat-shocked V. parahaemolyticus cells (31). The biotin-labeled samples were hybridized with avidinalkaline phosphatase (Bio-Rad) and visualized in the presence of the color solution containing nitroblue tetrazolium and 5-bromo-4-chloro-3-indolyl phosphate following the instructions of the supplier (Bio-Rad).…”