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This project has three research objectives: 1) determine the environmental cues that govern biofilm formation; 2) determine the essential metabolic networks for Salmonella enterica growth in the rhizosphere; and 3) identify genus-specific metabolic strategies between S. enterica and E. coli. The expected outputs of the project include activities, events, and products. This project is a data-driven research endeavor to investigate the basic biology of S. enterica and identify essential metabolic networks used for growth during plant colonization. <P>Our activities will include conducting metabolic experiments to analyze the growth of S. enterica and compare it to E. coli in the same environment. The students conducting research on this project will be mentored by the PI and attend events, such as conferences, to disseminate the results from their research.
Non-Technical Summary:<br/>
Americans are more likely to become ill with foodborne illness, i.e, salmonellosis, from consumption of fresh produce than from meat products. Salmonella enterica is the number one cause of bacterial food-borne illness in the US and outbreaks of foodborne illness associated with fresh produce are rising. Once plants become colonized by S. enterica, the produce cannot be decontaminated. S. enterica attaches in an irreversible manner to plant tissue, including cantaloupe rind, lettuce leaves, alfalfa roots, and tomato fruit skin. Neither agricultural processors nor consumers can wash S. enterica from produce completely. The only "kill-step" for fresh produce is irradiation which is commercially nonviable due to consumer reluctance to purchase irradiated foods. Therefore, investigating the basic biology of S. enterica and identifying how the pathogen grows during plant colonization are paramount to reducing foodborne illness caused by contaminated fresh produce. We think that S. enterica grows differently between the well documented animal and less studied plant environments. Knowledge of these processes will allow development of targeted intervention strategies.
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Approach:<br/>
To identify the cues that govern biolfilm formation, we will map the regulational hierarchy of diguanylate cyclases and characterize their regulatory signals. To identify the essential metabolic networks used by S. enterica during lettuce rhizosphere colonization, we will identify the most abundant proteins produced in this environment. We will use the proteomic data to map the essential metabolic networks using constraint-based models of metabolism. We then will predict what metabolic reactions and enzymes would be needed to produce new cells. To determine whether the reduced number of salmonellosis outbreaks compared to illness from Shiga-toxin producing E. coli from contaminated lettuce has an underlying biological basis, we will compare essential metabolic networks between S. enterica and E. coli using flux based analysis.