Abstract

Bacillus cereus is a toxin producing bacterium responsible for food-borne toxi-infections. To monitor the ability of the food-borne opportunistic pathogen Bacillus cereus to survive during minimal processing of food products conditions were established which allowed the cells to adapt to heat and acid stresses. Cells were grown in chemostat at different pH (7.0 and 5.5) and at a growth rate of 0,2 h-1 . Cells were submitted during 40 minutes to an acid shock at pH 4 or to a heat shock at 50°C. The effect of preadaptation at a subletal temperature (42°C -15 min) was studied. Cells grown at low pH (pH 5.5) shown an acid stress adaptation with induction of an Acid Tolerance Response (ATR). Cross-adaptations was observed between thermotolerance and acidotolerance which suggested that a common mechanism was involved in the acid and heat stress responses in B. cereus ATCC 14579. Adaptive levels of stressor were found to induce the over expression of different genes encoding classical heat shock proteins such as dnaK, dnaJ sigB and GroEL and gene involved in internal pH homeostasis encoding ATPase, arginine decarboxylase or deiminase and lysine decarboxylase activities. These data shown that during mild processing, a cross-protection between acid and heat was occurred in B. cereus. These common mechanisms between acid and heat stress response may result in increasing survival of B. cereus cells in foods and can rising the pathogenicity of this bacteria. The virulence of this bacterium poses a major problem in public health in food poisoning.