Formulation of Culture Media for Conductimetric Assays: Theoretical Considerations

Abstract

Summary: The basic theory of electrolytic conductivity in solutions is described and a model is proposed which allows the direction and relative rates of change of conductivity in microbial cultures to be predicted. Guidelines are presented to enable nutrients to be selected so as to maximize conductivity changes. It is shown that a major consideration in any strategy to maximize conductivity changes in cultures must be to direct as many metabolic activities as possible to act in concert in the production or consumption of protons, and to combine this with use of a pH buffer that exhibits a large change in conductivity on taking up or losing a proton. The ability to predict conductivity changes in microbial systems should permit the rational design of culture media for the selective enumeration of microbes by conductimetric methods and the development of other kinds of conductimetric assays.