[Effect of pH on cea gene expression in cells irradiated with UV-light and unirradiated Escherichia coli cells].

The effect of pH on the expression of the cea gene encoding colicin EI in Escherichia coli was investigated by measuring the beta-galactosidase activity in the UV-irradiated growing cells carrying the cea-lacZ fusion. Maximum activity was observed at pH 7, and inhibition of expression was observed at pH 6 and pH 8. Treatment of the irradiated cells with 50-mM acetate increased inhibition at pH 6.0-7.5. No correlation between cea expression and the rate of cell growth was observed at different pH levels. Preliminary treatment with acetate at pH 7 reduced the expression of the recA gene, which participates in the regulation of the cea gene to 33% in irradiated cells and to 25% in nonirradiated cells.