Isolation of F' plasmids carrying a portion of the Salmonella typhimurium histidine transport operon

Abstract

The transposable drug resistance element TnWO was employed as a region of homology to direct the insertion of TnJO-containing derivatives of F'Bs114 lac into the chromosome of a Salmonella typhimurium strain that carries a TnlO insertion in the histidine transport operon. Based on the direction of transfer of the resulting Hfr strains, the chromosomal TnlO insertion was determined to be in orientation "A." New F' plasmids were selectively generated from one of the Hfr strains. The F' factors carry an intact dhuA hisJ portion of the histidine transport operon. A Southern hybridization revealed that one of the F' plasmids was formed by a type II excision event.