Effect of the virulence associated 47 megadalton plasmid of Yersinia pestis on permeability to gentian violet and sensitivity to novobiocin.

The loss of the 47 megadalton (Mdal) plasmid of Yersinia pestis resulted in increased gentian violet uptake and increased sensitivity to novobiocin. The addition of calcium caused a decrease in gentian violet uptake and a decrease in novobiocin sensitivity independent of the plasmid. Differentiation of cells bearing and lacking the plasmid was accomplished using novobiocin in the presence of calcium at 26 degrees C. The novobiocin resistance levels of cells lacking the 47 Mdal plasmid and cells with the plasmid, but with an insertion in or a deletion in, or encomposing, the calcium dependence region of this plasmid, indicated that the resistance to novobiocin was not associated with the calcium dependence region, but was associated with a separate 47 Mdal plasmid region. Examination of Yersinia pseudotuberculosis and Yersinia enterocolitica isolates demonstrated that functionally similar sites are present on the plasmids that encode for calcium dependence in these species.