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This project will begin to identify rpoS-regulated proteins that confer acid tolerance to 0157:H7 strains and the factors that contribute to the production and turnover of these proteins. The goal of these studies is to identify processing or storage conditions that decrease production or increase turnover of rpoS-regulated proteins.These findings will provide industry and public health agencies with data to identify additional control practices and further our understanding of the pathogenesis and survival of this important foodborne pathogen.
Escherichia coli 0157:H7 has emerged as a major foodborne pathogen since the first reported outbreak in 1982. Outbreaks involving apple cider, fermented sausage, and yogurt have focused attention on the acid tolerance properties of E. coli 0157:H7 strains. In addition to promoting survival in acidic foods, it has been hypothesized that acid tolerance may be a contributing factor to the low infectious dose of this pathogen. One of the acid-tolerance systems identified in E. coli 0157:H7 is controlled by a sigma factor,i.e. E538, encoded by rpoS. rpoS-controlled acid tolerance in E. coli 0157:H7 is not due to acid adaptation as cells do not require prior exposure to acidic conditions to become tolerant to low pH. E. coli 0157:H7 in which the rpoS gene has been inactivated are sensitive to acid, heat, and salt, and their survival in acidic foods, i.e. fermented sausage, is significantly reduced.