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The goal of this cooperative research project is to determine the molecular basis for the development of sanitizer tolerance in Listeria monocytogenes. One objective this research is to determine gene expression differences in planktonic and biofilm Listeria monocytogenes subjected to oxidative and quaternary ammonium sanitizer stresses. A second objective is to assess the contribution of genes up-regulated in response to oxidative and quaternary ammonium stress to biofilm formation and stress tolerance.
APPROACH: Gene expression information for two strains of L. monocytogenes will be obtained by microarray hybridization analyses of mRNA from the following cell types: Untreated planktonic cells Untreated biofilm cells Biofilm cells treated with hydrogen peroxide Biofilm cells treated with QAC Planktonic cells treated with hydrogen peroxide Planktonic cells treated with QAC Gene expression comparisons will include: Planktonic versus biofilm cells Planktonic cells before versus after hydrogen peroxide exposure Planktonic cells before versus after QAC exposure Biofilm cells before versus after hydrogen peroxide exposure Biofilm cells before versus after QAC exposure The role of genes will be confirmed by constructing specific mutations of genes indicated by microarray analysis and determining the phenotype of the mutants.