Effects of temperature and cell number on the production of hemolysin by Vibrio parahaemolyticus
2000
Siriporn Stonsaovapak (Kasetsart Univ., Bangkok (Thailand). Institute of Food Research and Product Development)
Two strains of Vibrio parahaemolyticus, ATCC 17802 Kanagawa negative (K-) and ATCC 27519, Kanagawa positive (K+) were used in this study. The effect of temperature on the production of hemolysin was studied in trypticase soy broth (TSB) with 3 percent NaCl. Maximum hemolysin productions by both strains were obtained at 35 deg C with little or no production of hemolysin at 4 deg, 10 deg and 42 deg C. The K+ strain consistently produced higher titers of hemolytic activity than its K- counterpart. Hemolysin production at lower temperatures (4 deg and 10 deg C) could only be detected after 10 or 12h in TSB with 3 percent NaCl. At 20 deg, 25 deg, 30 deg and 35 deg C in this medium, production of hemolysin could be detected after 6 or 8h of incubation. At these same temperatures, both K+ and K- strains produced comparable cell numbers by 12h; however, the greatest hemolysin production occurred at 35 deg C. This indicates that temperature, rather than cell numbers, determined the total hemolysin produced during a controlled incubation time period.
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