Abstract
Gentian violet resistance was used to select mutants of Yersinia pestis with altered cell envelope permeability. Mutants in one class lacked the 6 and 61 megadalton (Mdal) plasmids, but retained the a47 Mdal plasmid associated with calcium dependence. Mutants in a second class retained all three plasmids. Ev76S7 cells were phagocytized to a greater extent than the parental cells following growith at 37 degree C, but survival and growth within peritoneal phagocytes and the LD sub(50)'s of cells with and without the 47 Mdal plasmid were not altered by the loss of protein J. The authors conclude that protein J -- LPS interactions are not required for virulence, and that the reduced virulence of cells lacking the 47 Mdal plasmid does not result from the altered protein J -- LPS interactions which are known to result from loss of the plasmid.