Expression of a plasmid borne ethidium resistance determinant from Staphylococcus in Escherichia coli: Evidence for an efflux system



Abstract A 1.1-kilobase (kb) DNA fragment derived from a staphylococcal plasmid specifying resistance to ethidium has been cloned into plasmid vector pUC9 in Escherichia coli. This fragment conferred resistant to ethidium and also to cetyltrimethyl ammonium ion in this host. Studies with labelled ethidium indicated that the basis of resistance was extrusion from the cell by an efflux system.