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The short-chain organic acids (SCOAs), acetic and propionic acids, are used widely as food preservatives. The production of these two acids plus butyric acid in the colon by anaerobes serves as a mechanism for controlling the numbers of enterobacteria (which can be pathogens) in this organ. It has been found in this study that the acid tolerance of cells initially grown at near neutral pH (6.5) to a lethal pH of 3.5 is enhanced by their exposure to 0.1% propionate or butyrate. The data also indicate that the inducible arginine and lysine decarboxylases are important for the survival of Escherichia coli exposed to a combination of mildly acidic pH (5.5) and 0.5% butyrate. This study suggests that the presence of SCOAs could trigger an adaptive survival response which may be important in the survival of food-borne pathogens.