Changes in the Survivability of Marine Vibrio sp. under Hyper KCl Stress in the Presence of Betaine as Well as with Exposure to 37oC.

摘要

Survivability at hyper KCl stress was examined at 30oC and 37oC in the presence and absence of an osmoprotectant by using resting cells prepared from marine Vibrio sp. grown at early stationary phase. Survivability was decided by counting colonies. The number of initial cells, 10~(7.1 ± 0.2)(CFU·mL~(-1)), was reduced to 10~(5.1 ± 0.5)and < 10~(1.0)(CFU·mL~(-1)) at 30oC and 37oC, respectively, by the exposure of resting cells, that were prepared from cells grown for 8 h at 0.5 M NaCl at 30oC, to 1.2 M KCl and 50 mM NaCl for 3 h. Betaine externally existed as a final concentration of 50 mM mitigated hyper KCl stress to the resting cells at 37oC. The number of surviving cells was maintained 10~(4.9 ± 0.3)(CFU·mL~(-1)) when resting cells, 10~(6.5 ± 0.1)(CFU·mL~(-1)), that were prepared from pre-adapted cells to relatively high concentration of KCl in the growth for 10 h at 0.8 M KCl and 50 mM NaCl at 37oC, were exposed to 1.2 M KCl, 50 mM NaCl, and 50 mM betaine at 37oC for 3 h. The results indicate that osmoadaptation system(s) in resting cells is temperature sensitive and betaine functions to mitigate hyper KCl stress to the resting cells at 37oC.