Induction of the SOS response in Escherichia coli by 4-quinolone antimicrobial agents

The induction of the RecA protein in strains of Escherichia coli was demonstrated for five 4-quinolone compounds. Using a recA∷lac fusion, the expression of the recA gene was quantified for each agent. Induction was shown to be time and concentration-dependent. At a certain concentration (dependent on each 4-quinolone) maximum induction was observed. Above this concentration, reduced induction was observed with an increase in 4-quinolone concentration. The inducing concentration of each 4-quinolone correlated well with the antibacterial activity of each agent.