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The proteins induced by heat and cold shock in Listeria monocytogenes (pathogenic for humans) and L. innocua (nonpathogenic) strains were analyzed by two-dimensional (2-D) electrophoresis with the help of a computerized 2-D gel analysis system. Heat (49 degrees C) and cold (4 degrees C) shock repressed roughly half the number of proteins synthesized at normal temperature (25 degrees C) and decreased the level of numerous other proteins. Conversely, the synthesis of a great number of proteins was enhanced and novel proteins appeared upon temperature stress. There were more proteins induced in the L. monocytogenes strain than in the L. innocua strain. Each stress induced a set of specific proteins. There was overlap between these sets of proteins induced by heat and cold shock. Furthermore, a number of heat or cold shock proteins were found to be induced in both Listeria species and by both heat and cold shock in both species. The induction by heat shock was more intense than that by cold shock. The most strongly induced common stress protein of Listeria had a molecular mass of 17.6 kDa and an isoelectric point of 5.1.

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