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The goal of this project is to determine extent to which biofilm cells of L. monocytogenes adapt to sublethal stresses, to determine the physiological mechanism of this adaptation, and to determine if this adaptation is associated with persistence in the processing plant. This study will focus on heat, oxidative, and acid stresses, as these are the stresses most relevant to survival in the processing plant environment. <P>
Specific objectives are: <OL> <LI> Determine the relationship between adaptation of biofilm L. monocytogenes to heat, oxidative, and acid stress and the ability of strains to persist in processing plant environments. Changes in rate of biofilm growth, oxidation, heat and acid resistance of resulting biofilms, and changes in the amount of extracellular polymeric substances produced by the biofilms from heat, oxidative and acid stressed cells will be determined for persistent and nonpersistent processing plant isolates. <LI> Determine physiological mechanisms responsible for biofilm stress adaptation. Identify specific proteins that are up or down regulated by biofilm L. monocytogenes in response to repeated sublethal heat, oxidative or acid stress. Use this information to describe the physiological basis of biofilm adaptation
NON-TECHNICAL SUMMARY: Certain strains of Listeria monocytogenes are able to persist in food processing environments for long periods of time. This pathogen can then contaminate processed product resulting in disease outbreaks and product recalls. The project will characterize persistent and nonpersistent strains of Listeria monocytogenes relative to the differences in response to stresses that are associated with suvival in a food processing environment. Such characterization will lead to understanding of why some strains of Listeria persist in the envioronment and lead to improved control procedures.
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APPROACH: We have isolated persistent and nonpersistent strains of L. monocytogenes from a ready-to-eat poultry processing plant over the course of year. We will determine the ability of these strains to produce biofilms that adapt to processing plant stresses. The physiological adaptation will be characterized using proteome analysis. We will identify genes involved in the biofilm stress response using the results of proteome analysis. These results will be correlated with persistent phenotype.