Relationships between curing of the F episome by rifampin and by acridine orange in Escherichia coli.

Subinhibitory doses of rifampin cured F(+)Escherichia coli cells from the episome. The target of the drug was transcription because E. coli mutants with a ribonucleic acid polymerase resistant to rifampin were not cured. The experimental conditions required for optimal curing with rifampin very closely resembled those required for curing with acridine orange. Mutants were found which are more resistant to curing by both acridine orange and rifampin. Probably the two drugs affect a common metabolic step, or alternatively they may inhibit the synthesis of a factor which is necessary for the replication of the episome.