Molecular Characterization of Pathogens and Their Responses to Environmental Factors

Approach: Stresses in foods and food processing environments that induce adaptations in foodborne
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, and using proteomics tools. 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
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 identification, quantification, and differentiation of pathogens
in foods and within processing environments.