The plasmid curing action of imipramine in Escherichia coli K12.

Curing of an F-prime plasmid by imipramine was most efficient on bacteria growing semianaerobically at 37 °C. The plasmid curing effect of imipramine was increased in the presence of methylene blue, whilst fluorescein, chlorpromazine-sulphoxide and tetraoxyanthrachinon antagonized the plasmid curing action of the drug. In addition to its plasmid curing effect, imipramine treatment selected for Lon mutants at high frequency. Lon mutants show increased resistance to the drug but cured strains, if Lon + , are not resistant.