The Loss of Viability of Bacteria in Suspension Due to Changing the Ionic Environment

SUMMARY: Following the accidental discovery and subsequent confirmation of an 80% loss of viability in a suspension of Escherichia coli when the ionic environment was changed from phosphate buffer to Ringer's solution, and of similar losses after changes in the reverse direction, the behaviour of other organisms was studied. Clostridium butyricum, Streptococcus lactis, Escherichia coli , and Micrococcus candidus gave positive results, Mycobacterium smegrmatis and a brewer's yeast did not. The survey included variations in the conditions, mostly with E. coli. Minor constituents of the solutions or alteration of their pH modified the effect, e.g. that of 1% NaCl in place of Ringer's solution or of pH 8·0 instead of the usual pH 7·2, was quite different. Also, the addition of glucose, sodium thioglycollate, or methylene blue diminished it, with one exception in the case of glucose. Mic. candidus responded if the solutions were chilled, but not at room temperature. With electrolyte concentrations below about 0·02 M there was no effect. Various other changes of anions were effective, as also was change from a univalent to a bivalent cation. A second treatment, following the necessary intermediate reverse change which had no effect, caused another smaller mortality. This reduced sensitivity gave a diminished loss which persisted through many subsequent subculturings.