Abstract

Exposure of Escherichia coli strain MC4100 to various concentrations of phenol at temperatures higher than 20℃ led to induction of stress proteins such as GroEL and DnaK, as analyzed by SDS-PAGE and Western blotting methods. The optimum range of phenol concentration for the induction of GroEL and DnaK was slightly different at each temperature of bacterial growth and phenol treatment. The level of GroEL increased as the temperatures of growth and phenol treatment were increased from 30℃ to 40℃. The level of induced FroEL was maximal in the wild type cells which had been grown and treated by 2000㎍/㎖ phenol at 40℃. In contrast to GroEL, the level of DnaK decreased as the temperatures of growth and phenol treatment were increased from 25℃ to 40℃. Dnak was maximally induced in the cells grown and exposed to 1000㎍/㎖ phenol at 25℃. In rpoH mutant cells KY1601, GroEL was not additionally induced by phenol treatment and DnaK was not even detectable under normal and phenol stress conditions. Viability of cells under the same conditions of phenol treatment showed that the phenol resistance in much more induced in wild type cells than rpoH mutant cells. These results suggest that the induction of GroEL and DnaK is required for the enhanced viability of cells under conditions of phenol stress.

• Keywords: Escherichia coli; DnaK; GroEL; heat shock proteins; phenol stress