Regulation of cyclic AMP synthesis in Escherichia coli K-12: Effects of the rpoD800 sigma mutation, glucose, and chloramphenicol

Abstract

An immediate 12-fold inhibition in the rate of β-galactosidase synthesis occurs in Escherichia coli cells containing the mutant sigma allele rpoD800 after a shift to 42°C. In the present study we characterize the nature of the inhibition. The severe inhibition of β-galactosidase synthesis was partly relieved by cyclic AMP (cAMP). We inferred that the inhibition might be mediated by a decreased intracellular concentration of cAMP. Consistent with this inference, the rate of cAMP accumulation in mutant cells after a temperature upshift was depressed relative to that in wild-type cells. Glucose and chloramphenicol, two agents known to inhibit differentially β-galactosidase mRNA synthesis, caused a similar inhibition in the rate of cAMP accumulation. Thus, three diverse stimuli, glucose, chloramphenicol, and a temperature-sensitive sigma mutation, appear to affect β-galactosidase synthesis by regulating the synthesis of cAMP.