Agents capable of eliminating F8-episome from a male strain of Escherichia coli were selected by two methods. The first method was based on the conversion of the strain from galactose fermentative to non-fermentative and the second on the conversion from RNA phagesensitive to resistant. Two antibiotics, sarkomycin and primocarcin, were selected. Sarkomycin was less active than acridine orange, but was less toxic.
