STUDIES ON THE NUTRITION AND PHYSIOLOGY OF PASTEURELLA PESTIS

Abstract

A factor present in milk which was required for the growth of virulent strains of P. pestis at 37[degree]C was identified as the Ca ion. Virulent strains required 0.002 to 0.004 [image] Ca ions in a defined basal medium containing 0.02 [image] Mg ions. Avirulent strains grew in the basal medium without Ca. The presence of an adequate amount of Ca prevented loss of virulence which generally occurs at 37[degree]C among virulent strains of P. pestis during prolonged incubation under aerobic conditions. Sr and Zn were able to replace the Ca requirement. Evidence was obtained which indicated that both virulent and avirulent strains require Ca for growth at 37[degree] C. In avirulent strains the Ca requirement is replaceable by high concentrations of Mg ions; whereas in virulent strains, high amounts of Mg appeared to antagonize growth.