Loss of an episomal fertility factor following the multiplication of coliphage M13

Summary The infection of an Escherichia coli F merodiploid strain by the male specific bacteriophage M13 followed by its multiplication and release, induces a conversion of the cells to the F^- phenotype. Evidence is presented to show that this conversion is associated with a) the simultaneous loss of three F determined properties, b) the loss of a molecular form of DNA characteristic of F and c) the ability of the converted cells to be conjugally reinfected with the same F factor. These findings indicate that the F episome is physically eliminated from the cells that survive M13 infection.