title: Modulation of responses of Vibrio parahaemolyticus O3:K6 to pH and temperature stresses by growth at different salt concentrations.
abstract: Vibrio parahaemolyticus inhabits marine, brackish, and estuarine waters worldwide, where fluctuations in salinity pose a constant challenge to the osmotic stress response of the organism. Vibrio parahaemolyticus is a moderate halophile, having an absolute requirement for salt for survival, and is capable of growth at 1 to 9% NaCl. It is the leading cause of seafood-related bacterial gastroenteritis in the United States and much of Asia. We determined whether growth in differing NaCl concentrations alters the susceptibility of V. parahaemolyticus O3:K6 to other environmental stresses. Vibrio parahaemolyticus was grown at a 1% or 3% NaCl concentration, and the growth and survival of the organism were examined under acid or temperature stress conditions. Growth of V. parahaemolyticus in 3% NaCl versus that in 1% NaCl increased survival under both inorganic (HCl) and organic (acetic acid) acid conditions. In addition, at 42 degrees C and -20 degrees C, 1% NaCl had a detrimental effect on growth. The expression of lysine decarboxylase (encoded by cadA), the organism's main acid stress response system, was induced by both NaCl and acid conditions. To begin to address the mechanism of regulation of the stress response, we constructed a knockout mutation in rpoS, which encodes the alternative stress sigma factor, and in toxRS, a two-component regulator common to many Vibrio species. Both mutant strains had significantly reduced survival under acid stress conditions. The effect of V. parahaemolyticus growth in 1% or 3% NaCl was examined using a cytotoxicity assay, and we found that V. parahaemolyticus grown in 1% NaCl was significantly more toxic than that grown in 3% NaCl.
authors.affiliation: Department of Biological Sciences, University of Delaware, Newark, DE 19711, USA.
authors.forename: W Brian
authors.initials: WB
authors.lastname: Whitaker
authors.forename: Michelle A
authors.initials: MA
authors.lastname: Parent
authors.forename: Lynn M
authors.initials: LM
authors.lastname: Naughton
authors.forename: Gary P
authors.initials: GP
authors.lastname: Richards
authors.forename: Seth L
authors.initials: SL
authors.lastname: Blumerman
authors.forename: E Fidelma
authors.initials: EF
authors.lastname: Boyd
mesh_terms: D000143:Acids / Q000633:toxicity*; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics; D002262:Carboxy-Lyases / Q000096:biosynthesis; D004268:DNA-Binding Proteins / Q000235:genetics; D017353:Gene Deletion; D050296:Microbial Viability / Q000187:drug effects / Q000528:radiation effects; D012492:Salts / Q000378:metabolism*; D012808:Sigma Factor / Q000235:genetics; D013312:Stress, Physiological; D013696:Temperature; D014157:Transcription Factors / Q000235:genetics; D014736:Vibrio parahaemolyticus / Q000187:drug effects* / Q000254:growth & development / Q000528:radiation effects*
chemical_list: D000143:Acids; D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D012492:Salts; D012808:Sigma Factor; D014157:Transcription Factors; C069567:sigma factor KatF protein, Bacteria; C066719:toxR protein, bacteria; D002262:Carboxy-Lyases; C021520:lysine decarboxylase
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