Adaptation of Escherichi coli to elevated temperatures involves a change in stability of heat shock gene transcripts.

Bacteria respond to shift-up in temperature by activating the heat shock response - induction of a large number of heat shock genes. This response is essential for adaptation to the higher temperature and for acquiring thermotolerance. One unique feature of the heat shock response is its transient nature - shortly after the induction, the rate of synthesis of heat shock proteins decreases, even if the temperature remains high. Here we show that this shutoff is due to a decrease in the transcript stability of heat shock genes. We further show that the modulation of stability of mRNAs of heat shock genes is maintained by the cold shock protein C - CspC - previously shown to affect transcript stability of specific genes. Upon shifts to higher temperatures the level of this protein decreases due to proteolysis and aggregation, leading to a reduced stability of mRNAs of heat shock genes. The temperature-dependent modulation of transcript stability of heat shock genes constitutes a novel control of the bacterial response to temperature changes.