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<OL> <LI> To study the effect of stresses on bacterial survival and on cross-protection/cross-sensitization against subsequent stresses; <LI> To examine the effects of stress conditions on bacterial virulence and expression of virulence-associated genes; <LI> To develop methods for detection of stressed/injured pathogens.
The genetic defects of L. monocytogenes cold-sensitive and osmotic-sensitive mutants will be identified to determine genes required for the organism to grow under conditions of cold stress. The effect of exposure to stress on cross protection or cross sensitization to subsequent stresses will be asasessed in food-born pathogens. The role of quorum sensing in the regulation of cellular functions and the effects of stresses on the growth, survival, inactivation, and gene expression of Campylobacter in foods will be studied. Reporter vectors containing promoters of stress response genes will be constructed and used to monitor gene expression in real time under different stress conditions. The role of curli in E. coli O157:H7 will be investigated to determine the role of these structures in survival of the organism as well as in attachment to meats. The effects of stresses on Shiga toxin induction and on growth and survival of E. coli will be assessed. Methodologies for detection of pathogens that are stressed or injured in foods and during food processing will be developed.