It was earlier shown that expression of the
microcin C51 operon in Escherichia coli cells is activated upon decelerated growth of cells during their transition to the stationary growth phase and depends on the sigmaS subunit of
RNA polymerase. Using a single-copy construct containing the cloned promoter region of the
microcin C51 operon and a promoterless lac operon (P(mcc)-lac), it was shown that the promoter of the
microcin operon was also induced by stress caused by the transition of cells at the exponential growth phase into the medium without
glucose as a sole
carbon source. Activation of P(mcc)-lac expression upon severe
glucose starvation occurred in rpoS+ and rpoS- strains. In cells carrying the rpoD800 mutation that renders the sigma70 subunit of
RNA polymerase temperature-sensitive, an activation of P(mcc)-lac expression was observed at nonpermissive temperature, in contrast to its complete inhibition in E. coli cells at the phase of delayed growth. Other stressors-
nitrogen starvation, high temperatures, osmotic shock,
tetracycline and
chloramphenicol-did not activate P(mcc)-lac expression in cells at the exponential growth phase.