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Chapter 8 : Molecular Mechanisms of Microbial Survival in Foods
Category: Food Microbiology; Applied and Industrial Microbiology
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This chapter describes the most important global regulator systems in representative food-borne pathogens and reviews the individual molecular mechanisms of survival against specific food-related stresses. It talks about representative gram-positive bacteria (Listeria monocytogenes and Staphylococcus aureus) and gram-negative (Escherichia coli, Salmonella, and Campylobacter) food-borne pathogens which have been thoroughly studied. Weber et al. have classified all the RpoS-regulated genes into six major categories based on their functions: metabolism, regulation, transport, adaptation to stress, protein processing, and unknown. Gram-negative and gram-positive bacteria use global strategies in their response to osmotic stress as well as some unique species-specific responses. The chapter reviews the current knowledge on the molecular response to osmotic stress as manifested by a few food-borne pathogens. In most bacteria, glycine betaine is the most effective osmoprotectant, as it increases the volume of available water in the cytoplasm. Low-temperature storage of foods is an extremely successful preservation technology. Advancement of one's knowledge about the molecular basis for bacterial survival under stressful conditions is critical to the assurance of safe and palatable foods, whether using traditional or novel preservation technologies. The advent of genomics-, proteomics-, and metabolomics-based techniques has accelerated one's knowledge of the components involved in novel stress responses. In addition, the availability of an increasing number of fully sequenced bacterial genomes should facilitate further advances in the field of bacterial stress responses.
Diagram of σS regulation and some of the main factors involved in its activation (+) or inhibition (−). cAmP, cyclic AMP; CRP, catabolite repression protein.
Heat shock genes of gram-positive bacteria as organized by class a