Molecular Characterization of Pathogens and Their Responses to Environmental Factors

Approach: Stresses in foods and food processing environments that induce adaptations in food-borne pathogens, potentially leading to increased survival and virulence will be studied in efforts to develop control strategies. Included will be conditions of cold, heat, acid, oxidative, and osmotic stress, as well as exposure to antimicrobials as they affect pathogen survival and cross protection against subsequent stresses. The molecular mechanisms underlying bacterial adaptation to stresses will be studied using DNA microarrays, consisting of genes of Salmonella, E. coli O157:H7, and Campylobacter. Cellular targets, such as enzymes and membrane proteins, involved in pathogen growth, which might be exploited to control the organisms in food, will be identified. To understand the effect of food-related stresses on bacterial quorum sensing, the production of autoinducers, including the N-acyl homoserine lactones and autoinducer 2, will be quantified in food-borne pathogens in response to food environment-related stresses. Peptides are known to act as autoinducers in Gram-positive bacteria; therefore, potential signaling peptides and other types of autoinducers will be identified in L. monocytogenes and C. perfringens. The role of cell-to-cell signaling in biofilm formation will be determined, and compounds that may inhibit quorum sensing will be identified. Finally, efficient sample processing techniques and genetic-based technologies, including DNA microarrays and the PCR, will be developed for detection, identification, typing, and speciation of food-borne pathogens, in particular, bacteria that were stressed/injured due to food-environment-related conditions. The methods will allow detection, quantification, and differentiation of pathogens in foods and within processing environments.