Curing effect of clorobiocin on Escherichia coli plasmids.

Clorobiocin, an inhibitor of the gyrB subunit of DNA gyrase, was used for the curing of some Escherichia coli plasmids. Of the plasmids studied, ampicillin resistant R28K and a miniplasmid derived from R1drd-19 were effectively eliminated. We also succeeded in eliminating the ColA factor from E. coli strain B834(pBS103), which was resistant to the effect of currently used curing agents. Although a derivative of ColE1-pBR322 was effectively cured by clorobiocin, the ColE1 plasmid was resistant to its effect. The ColV plasmid determining virulence was effectively eliminated.