Heat and salt stress in the food pathogen Bacillus cereus.

Abstract

The effects of stresses imposed on bacterial contaminants during food processing and treatment of packaging material were evaluated on the food pathogen Bacillus cereus. Conditions were established which allowed the cells to adapt to heat, ethanol and hydrogen peroxide stresses, but not to osmotic shock. Cross protection between stresses indicated a clear hierarchy of resistance with salt protecting against hydrogen peroxide, which protected against ethanol, which protected against heat shock. The cultures were shown to be most sensitive to heat, ethanol and oxidative stress at mid-exponential phase and to become resistant at stationary phase. Adaptive levels of stressor were found to induce synthesis of general stress and stress-specific proteins and differential accumulation of proteins was demonstrated between heat- or salt-stressed and unstressed cells. Sequencing revealed that a number of glycolytic enzymes were regulated by heat and osmotic shocks and that the chaperone GroEL was induced by heat shock. The implications of the physiological data in designing storage and processing conditions for food are discussed. The identification of stress-regulated proteins reveals a clear role for glycolysis in adaptation to heat shock and osmotic stress.