The SOS induction of umu'-'lacZ fusion gene by oxidative damage is influenced by polyamines in Escherichia coli

We report that polyamines have an effect on the SOS response of the umu ope ron in polyamine-deficient mutant and wild-type Escherichia coli strains ca rrying the umu'-'lacZ fusion. H2O2 effectively induces umu'-'lacZ in the wi ld type, but not significantly in the mutant strain. Exogenous polyamines d id not restore the umu induction in the mutant to the wild-type level. In l ogarithmically growing cells, the basal expression of umu gene in the mutan t is about five times higher than that of the wild type. The addition of po lyamines to the growth medium markedly reduces the basal expression to the wild-type level. This reduction is due not to growth rate but to the polyam ine itself. Our results suggest that polyamines are essentially involved in the SOS induction of the umu operon in E. coli.