Osmotic stress conditioning for induction of acquired osmotolerance in Escherichia coli.

Escherichia coli cells exhibited osmotolerance and grew well even in hyperosmotic medium containing 1.2M NaCl (or 2.0M sorbitol) if they had been previously exposed to moderate osmotic stress for a short time (30min). Untreated cells showed repressed growth. This acquirement of osmotolerance against hyperosmolarity was dependent on the concentration of the osmoticum in the osmotic stress conditioning. The most effective conditioning occurred when almost the same moderate osmolarity of electrolytes (about 0.4-0.6M NaCl or KCl) and non-electrolytes (about 0.8-1.2M sorbitol or sucrose) was used as osmoticum. The acquired osmotolerance could be inhibited markedly by chloramphenicol or rifampicin, but not by nalidixic acid. Experiments with 35S-methionine incorporation suggest that the synthesis of several proteins might be related to the acquiring of osmotolerance.