Effect of Ca 2+ on the Synthesis of Deoxyribonucleic Acid in Virulent and Avirulent Yersinia

Abstract
Virulent and potentially virulent cells of Yersinia ( Pasteurella ) pestis produce virulence or V and W antigens (VW + ) but remain static at 37 C during aeration in enriched Ca 2+ -deficient media containing 0.02 m Mg 2+ . In this environment, which simulates mammalian intracellular fluid, VW + cells possessed a functional cytoplasmic membrane as judged by concentration of 14 C-isoleucine, release of 32 P, and consumption of oxygen at rates comparable to those of dividing cells cultivated with Ca 2+ . Furthermore, rates of protein and ribonucleic acid synthesis were essentially identical in dividing and static VW + cells and in mutant VW organisms. However, the rate of deoxyribonucleic acid (DNA) synthesis in static cells was about 10% of that observed in dividing organisms. Accordingly, bacteriostasis of VW + cells in the simulated intracellular environment is evidently caused by reactions directly associated with cessation of DNA synthesis rather than by alterations in the regulatory capacity of the cytoplasmic membrane.

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