Integration of the Vwa plasmid into the chromosome of Yersinia pestis strains harboring F' plasmids of Escherichia coli

Abstract

Conditional virulent strains of Yersinia pestis were used as recipients of an F-lac plasmid from either Escherichia coli 23.10S or E. coli CSH23. The transconjugants of Y. pestis were calcium independent; however, calcium dependence was restored after the loss of the E. coli plasmid. The plasmid contents of several Y. pestis F-lac clones were compared with those of the parent strains and several lac segregants. Although the 6- and 61-megadalton plasmids were detected in all strains tested, the Vwa plasmid was absent in the F-containing strains. The plasmid was evident, however, in the lac segregants derived from the F-lac clones. Results of Southern transfers indicated that the Vwa plasmid had integrated into the chromosome of Y. pestis strains harboring F-lac.