Effect of Time and Temperature upon Survival of Escherichia coli in Sodium Chloride. ∗

Summary

Suspensions of E. coli in 4.6 M NaCl stored under conditions which preclude cell division undergo at first a rapid decline in viable cells, but as the storage interval is extended the death rate continuously decreases until eventually it becomes negligible. Cells that endure the period of rapid decline are able to maintain themselves in the saline for long periods. This resistance is not heritable. In fact, once the cells are removed from the saline their resistance to it is lost. Generally, the higher the storage temperature the better is survival. Also, holding suspensions at a relatively high temperature (+2° or − 9°C) prior to subsequent storage at a low temperature (−22°C) improves survival at the low temperature. These data suggest that the tolerance to 4.6 M NaCl is acquired while the cells reside in the saline and does not exist preformed in a segment of the original population. Two hypotheses have been offered to account for the adjustment to NaCl tolerance.