Expression of a mutation affecting F incompatibility in the integrated but not the autonomous state of F

Abstract

Previously, a mutant Hfr strain [Escherichia coli] in which incompatibility between the integrated F factor and an autonomous F-prime (F) factor was abolished was described. The mutation (inc) was located in the integrated F factor. F-prime factors isolated from the mutant Hfr strain have the same incompatibility behavior as those isolated from normal Hfr strains. Reintegration of these F'' factors into the chromosome restores the Inc- phenotype characteristic of the mutant Hfr. The inc mutation thus affects incompatibility between integrated F and autonomous F(Fi-Fa incompatibility) but not incompatibility between 2 autonomous F factors (Fa-Fa incompatibility). The implications of this finding for the mechanism of plasmid incompatibility are discussed.