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The goal of the proposed project is to improve the fundamental understanding of early-stage pathogen contamination mechanisms in fresh produce by linking surface properties, physics of small-scale water organization and resulting nutrient availability with bacterial attachment, motility, growth and colonization on fresh produce. We propose to achieve this goal with experimental investigations and with modeling. Our specific objectives include: To experimentally characterize attachment of bacteria to fresh produce and model surfaces as influenced by surface properties, hydration status and microscale water configuration; To develop a computational model that couples microscale hydrodynamic processes and reaction-diffusion elements for simulating small-scale water arrangement and its dynamic changes that shape nutrient fluxes and cell motility thereof influencing bacterial attachment, survival, growth, dispersion and colony development on rough surfaces; To provide experimental support for the developed model via direct microscopic observation of bacterial growth, dispersion and colony development on model and fresh produce surfaces.
<p>NON-TECHNICAL SUMMARY:<br/>Fresh fruits and vegetables have been increasingly associated with outbreaks of foodborne illness. What are the mechanisms that allow foodborne pathogens to attach, survive, colonize or grow on produce surfaces? What are the critical factors affecting pathogen attachment and colonization? These questions are of direct relevance to the goal of the AFRI Food Safety, Nutrition, and Health program to protect human health by enhancing food safety through preventing and mitigating contamination. This project is a new cross-disciplinary effort that will bring recent advances in the areas of colloid and microbial attachment and transport processes in porous media and individual/agent-based modeling of microbial growth, communication and social behavior and microbial ecology, to the relevant field of food safety. The goal of the project is to provide
critical mechanistic understanding of early-stage pathogen contamination in fresh produce by linking surface properties (e.g., hydrophobicity and microscale morphology), hydro-physical conditions (hydration status and aqueous-phase configuration), and the resulting nutrient fluxes with pathogen attachment and in situ microbial population establishment. We will use laser scanning confocal microscopy to experimentally quantify microbial attachment and growth to identify the key surface properties and biophysical factors influencing bacterial attachment and colonization on fresh produce. We will develop an individual-based modeling platform that explicitly takes into account microscale geometrical features and aqueous-phase configurations and connectivity that shapes microbial attachment and colonization. This research will improve assessment of risks associated with pathogen contamination
of fresh produce as well as new insight into modern food pathogen control protocols and provide additional scientific basis for improving the protocols.<p>
APPROACH:<br/>We will (i) conduct novel experiments to identify key produce surface physicochemical properties and associated hydro-biophysical processes that control the critical steps (e.g., attachment, survival, and growth/colonization) leading to pathogen contamination of fresh produce; and (ii) develop an experimentally validated computational tool that will enable us to quantitatively predict pathogen behavior on produce surfaces, and on food matrix in general. The proposed study brings the expertise on colloid and bacterial attachment and transport processes in porous media and individual/agent-based modeling of bacterial growth, communication and social behavior and bacterial ecology, to the relevant field of food safety. We expect to provide a quantitative and predictive tool for addressing the key biophysical factors influencing bacterial attachment, survival
and colonization on fresh produce. Specifically, we will (1) elucidate bacteria attachment mechanisms on model and produce surfaces using confocal microscopy, (2) visulize bacteria growth and colonization on surfaces as affected by surface hydrophobicity and roughness, water content and distribution, and nutrient availability, (3) integrate surface characteristics and biological mechanisms into a spatially and temporally resolved and individually based modeling platform that explicitly tracks motions and life history of each cell in a simulation domain, and (4) use the new model as an instrumental tool to systematically quantify the effects of surface properties (e.g., hydrophobicity and microscale morphology), hydro-physical conditions (hydration status and aqueous-phase organization) and resulting motility and diffusional heterogeneity at microscale, and variable resource availability
on bacterial distribution, growth, dispersion, and colonization on fresh produce.</p>