Elucidating the factors and mechanisms influencing the formation of biofilms in food systems

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Background. With expanding production and distribution systems in Canada, foodborne pathogens have multiple access points into our food system. Linkages of biofilms (diverse microorganisms which attach to, and grow on, surfaces) to outbreaks of foodborne disease are on the rise due to their ubiquity and their resilience to sanitization and removal attempts. Efforts to derive biofilm-specific control strategies have not been successful; thus, more information on how biofilms survive stress is necessary. My discovery grant research seeks to advance such knowledge, with the long-range goal of developing strategies for industry to help prevent outbreaks. Program.  My research focuses on adaptive stress responses used by pathogenic bacteria when exposed to antimicrobial treatments after having been pre-conditioned by stresses experienced outside of the gastrointestinal tracts of their natural hosts. In these transient environments (e.g., during production, transport, storage) bacteria encounter various sub-optimal conditions (e.g., temperature abuse, pH, low nutrients), challenging them to adapt to a more stress-resistant form. Biofilms may be key in stress resistance; however, their role remains unclear, as do the role(s) played by other organisms that co-exist within complex biofilm communities. My research program therefore has two long-term objectives: 1) to elucidate physiological and molecular mechanisms involved in biofilm and bacterial adaptive resistance to antimicrobial agents, nanoparticles and environmental stressors, and 2) to improve the understanding of community-level responses and cross-protective interactions between pathogenic and non-pathogenic biofilm-forming organisms during stress events. Experiments will be conducted using known pathogens to elucidate responses, determined using proteomics, in bacteria and biofilms exposed to two phases of stress – a “conditioning” stress phase (low temperature and slow growth) like that found in the food production chain, followed by an "imposed" stress phase (i.e., antimicrobials or nanoparticles). Inducing mutations in proteins thought to play a role in stress resistance in the test organisms will allow functional (gene expression and survival) analyses to confirm which response elements are critical. These proteins will then be probed in biofilm communities exposed to stresses to determine their function in more complex systems. A comprehensive understanding of microbial stress response pathways will identify molecular targets for engineered biofilm control strategies. Other benefits to Canada resulting from this research includes improving the safety of the food supply, as well as training the next generation of scientists in the area of food safety to support industry growth in the agri-food sector as well as the sciences.