Physiology of the Heat Shock Response and Thermotolerance

It transpires that the heat shock genes of one single bacterial species are regulated by different mechanisms. Genes and operons controlled by one particular regulator are called regulons and, if there are at least two regulons in one species induced by the same stress factor, they form a stimulon. 

When bacterial cells are shifted directly from a low growth temperature to a lethal temperature, the cells are rapidly killed. However, if the cells are first preadapted by growth at a non-lethal temperature for 30 min, the rate of killing upon a shift to lethal temperature is dramatically decreased these cells have acquired thermotolerance. During the pre-adaptation phase a heat shock response is induced which leads to increased synthesis of heat shock proteins. 

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