Bacillus cereus: Aerobic Growth Kinetics

Abstract

Three strains of Bacillus cereus were cultured in brain heart infusion medium aerobically under conditions of variable temperature (5 to 42°C), sodium chloride concentrations (0.5–5%), pH (4.5 - 7.5), and sodium nitrite concentration (0 mg/L - 200 mg/L) to simulate conditions of normal and adverse food storage. Cultures were sampled at selected times, and plate counts were used to calculate growth curves under each condition. None of the three strains grew at 5°C, but growth did occur slowly at 8°C, and was most rapid at a temperature of 37°C. Growth occurred in media without additives in all pH's examined between 8 and 42°C. Decreasing the pH and increasing levels of sodium chloride and sodium nitrite increased the lag phase and generation times of the organism.