Characterization of a ColEl-Like Plasmid Isolated from Shigella sonnei

Abstract

A multicopy plasmid, 4.7 kb in size, was isolated from Shigella sonnei and named pKYl. This plasmid produces a colicin El-like bacteriocin (colicin El*) in E. coli cells. The cells harboring pKYl are immune not only to this bacteriocin but also to colicin El, and the cells harboring ColEl show immunity to colicin El * as well. Although these two plasmid DNAs have different cleavage maps and are compatible with each other, pKYl shows partial DNA homology with ColEl DNA. In this paper, we report the isolation and properties of several TnJ inserted pKYl mutants, and propose a preliminary genetic map of pKYl. It was also found that this plas-mid is not capable of self-transmission and is poorly mobilized by the F factor. ColEl is an E. coli plasmid, approximately 6.4 kb in size, and produces colicin E l, a kind of bacteriocin (1). E. coli cells harboring ColEl are immune to its lethal effects, but they remain sensi-ive to other bacteriocins. Recently, we isolated a multicopy plasmi