Response and tolerance of toxigenic Vibro cholerae O1 to cold temperatures

Survival and tolerance at cold temperatures, the differentially expressed cellular proteins, and cholera toxin (CTX) production were evaluated in Vibrio cholerae O1. Rapid loss of culturability and change to distinct coccoid morphology occurred when cultures of V. cholerae O1 were exposed to 5 degreesC directly from 35 degreesC. Also, cultures of V. cholerae first exposed to 15 degreesC for 2 h and then maintained at 5 degreesC failed to exhibit an adaptive response, instead a rapid loss of viable plate count was noticed. Results from Western blot experiments revealed the absence of a major cold shock protein, CS7.4. Also, a decreased level of CTX was noticed in V. cholerae O1 cultures exposed to 5 or 15 degreesC after first being exposed to 15 degreesC for 2 h, followed by transfer to 5 degreesC. Reduced expression of CTX at cold temperatures, compared to the cultures maintained at 35 degreesC, may be a result of decreased cellular metabolic activity. When V. cholerae O1 cultures were exposed to 15 degreesC for 2 h, elevated expressions of 8, 26 and 194 kDa, and decreased expression of 28 and 183 kDa proteins occurred. It is suggested that these differentially expressed cold-responsive proteins are involved in regulating culturability and conversion to a coccoid cell morphology in V. cholerae O1.