Transfer of the virulence plasmid of Yersinia pestis to Yersinia pseudotuberculosis.

Transposon Tn5 insertion derivatives of the virulence plasmid pYV019 of Yersinia pestis were transferred by P1 transduction into a plasmid-free strain of Y. pseudotuberculosis. One of these plasmid derivatives conferred virulence upon the Y. pseudotuberculosis strain. This strain had the ability to express temperature-inducible plasmid-coded outer membrane proteins and was also found to be Ca2+ dependent.