At relatively low temperature (30 oC) where low levels of HSPs are required, the intracellular level of a 32 remains low in E. coli (Straus and others 1987; Craig and Gross 1991). In a modest temperature increase (30 C to 42 C), marked stabilization of o 2 occurs immediately and HSP synthesis is rapidly induced 10- to 15-fold within 5 min, which is followed by a gradual decrease in the rate of production after. 20 to 30 min in E. coli (Lemaux and others 1978; Herendeen and others 1979; Yamamori and Yura 1980; Strauss and others 1987; Nagai and others 1991). Zhou and grew only at or below 2 C. On downshift of temperature, scription of the heat shock genes rapidly decreases A 10-fold decrease in or 32 activity was observed within 5 min after a shift from 42 C to 30 aC, compared to less. than 2-fold decreases in a levels in E coli (Straus and others 1989; Taura and others 1989).