RELATIVE IMPORTANCE OF ADDITIVE AND ANTAGONISTIC EFFECTS OF CATIONS UPON BACTERIAL VIABILITY

Abstract

Investigations during the last 5 years at Yale have indicated that, so far as their fundamental effect on bacterial viability is concerned, the various cations function only quantitatively. All appear in a certain concentration to favor bacterial growth (probably by increasing cell permeability) and in a higher concentration to inhibit bacterial growth (probably by decreasing permeability and ultimate rupture of the cell membrane). The concentration at which a given effect is produced, however, differs widely. This study of the influence of Na, K and Mg on bacterial growth in a simple synthetic medium indicates that many of the phenomena described as antagonism may be explained by the purely additive effects of individual cations concerned. If we assume that Mg is 8 times as effective as Na or Ca in a given concentration, curves plotted to show the effect upon viability of different concentrations are essentially the same whether we use either one of the 3 salts alone or a combination. Even the pH appears to follow this rule, although its potency at a given concentration is very high. The authors of course recognize that certain biochemical properties of bacteria as well as many properties of cells of higher plants and animals may be affected by cations in a specific fashion; but so far as the influence of cations upon bacterial viability is concerned, such true qualitative antagonism does not seem to be important.