Grant: Discovery Launch Supplement

Most antimicrobials that kill or inhibit growth of bacterial pathogens target the cell envelope (i.e. exterior of the bacterial cell). Cell envelope composition and structure, as well as the expression of cell envelope genes, are severely affected by environmental conditions. Given the unique environment of foods (e.g. pH, temperature, salt content) and food-related settings (e.g. use of sanitizers), it is imperative to understand how these conditions affect the structure and regulation of expression of cell envelope components, since this will in turn affect the successful implementation of antimicrobial strategies against foodborne pathogens. The human and animal pathogen Listeria monocytogenes (Lm) contaminates foods and poses a major threat as it can grow at refrigerated temperatures to potentially infectious levels for susceptible individuals. In elderly, immunocompromised, and pregnant individuals infection with Lm, or listeriosis, has a 20-30% mortality rate. Lm contamination of foods is particularly problematic for ready-to-eat (RTE) food products, which aren't cooked before consumption. Detection of Lm in high-risk RTE food products leads to product recalls which pose significant economic hardships to our food industry. Our previous research using Lm isolates from food recalls and outbreaks showed that the environment (e.g. temperature and pH), as well as Lm serotype, affect resistance to the bacteriocin nisin and to an anti-Lm phage cocktail in both a fresh-style cheese model and in cold-smoked salmon. Understanding the molecular strategies employed by Lm to counteract cell envelope-acting treatments in relevant food matrices would improve our use of antimicrobial strategies in foods and decrease potential outbreaks and recalls. The short-term goals of my research program are to: Aim1. Characterize expression of key Lm cell envelope constituents under food-relevant environmental conditions. Aim2. Identify genes essential for Lm growth in food-related matrices. The long-term vision of my program is to use this information to improve current and develop new strategies for foodborne pathogen control. Novelty and Significance: There is a current lack of understanding of how the food-specific environment affects the cell envelope composition of the important, deadly, and costly foodborne pathogen Lm. Given how cell envelope composition in turn affects the efficiency of antimicrobial strategies, it is imperative to fill this knowledge gap and harness our enhanced understanding for the discovery of novel, and improvement of current, control strategies for foodborne pathogens. My research to date has focused on understanding cell envelope stress response in different microbes, using an arsenal of microbiological, molecular, and biochemical techniques, therefore, my group has the unique and novel opportunity to translate and apply these approaches to better understand the survival strategies employed by Lm in RTE foods.