STUDIES ON THE NUTRITION AND PHYSIOLOGY OF PASTEURELLA PESTIS VI. A

Abstract
A differential plating medium containing magnesium oxalate was developed for the detection of avirulent variants in populations of P. pestis. The composition of this medium was based on the specific requirement for calcium ions by virulent cells for growth at 37[degree] C. An estimation of the mutation rate to avirulence among cells of the virulent Alexander culture yielded a value of 10-4 mutations per bacterial generation.