Analysis of the Osmotic Regulation of Thermotolerance in Salmonella and E. coli O157:H7 (1998-02730)

The addition of moderate or high concentrations of salts or sugars can enhance the high temperature tolerance of food pathogenic bacteria such as Salmonella and E. coli O157:H7. This enhanced thermotolerance is manifested both as increased growth rate at non-lethal high temperatures and increased survival at otherwise lethal high temperatures. These observations indicate that the addition of salts or sugars to food products as preservatives or flavor components can compromise the efficacy of high temperature treatment for the inactivation of contaminant organisms. We found that betaine, which is found at high levels in edible plants such as spinach and cereal grains, block the ability of salt additives to increase the thermotolerance of bacteria. Part of the research project will be to carry out a comprehensive characterization of all available structural relatives of betaine for their ability to counteract the induction of increasedthermotolerance by salt additives in food pathogenic bacteria. This procedure may uncover new food additives that might be used to increase the efficacy of thermal inactivation in food contaminating bacteria. A second component of the project will be to discover genes which are involved in the induction of increased heat tolerance by salt.
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The understanding of the mechanistic connection between high salinity and increased thermotolerance has the potential application that it might lead to the design of new antimicrobial compound that could lead to decreased survival of food pathogens during thermal processing.