Journal of Microbiology

Production of Stress-shock Proteins in Pseudomonas sp. DJ-12 Treated with 4-Hydroxybenzoate: Park, Sang Ho , Oh, Kye Heon , Lee, Kil Jae , Kim, Chi Kyung; J. Microbiol. 1998;36(4):273-279.

Abstract: Pseudomonas sp. DJ-12 can grow on 4-hydroxybenzoate (4HBA) at concentration of 5 mM or lower by degrading 4HBA for carbon and energy sources. The organisms were found to produce DnaK stress-shock protein when treated with several aromatic hydrocarbons including 4HBA. Those cells treated with 5 mM 4HBA exhibited increased tolerance to 10 mM concentration. In this study, the production of other stress-shock kproteins besides KnaK was examined in Pseudomonas sp. DJ-12 exposed to various concentrations of 4HBA, compraing the production of the proteins with their survival and degradation of 4HBA. The organisms could degrade 4HBA at 0.5 to 5 mM concentrations after 60 to 90 minutes of incubation. The survival rate of the organism decreased when treated with 4HBA at 10 mM or higher concentrations. The stress-shock proteins of DnaK, GroEL, and GroES were produced in the cells which were treated with 4HBA at 0.5 mM or higher concentrations for 10 minutes. Fifteen additional stress-shock proteins were produced in the cells which were treated with 5 mM 4HBA for 40 minutes. The DnaK and GroEL proteins in the cells gradually decreased upto 6 hours after the stress was removed from the culture.

Synthesis and Requirement of Escherichia coli Heat Shock Proteins GroEL and DnaK for Survival under Phenol Stress Conditions: Jeon, Taeck Joong , Lee, Kil Jae; J. Microbiol. 1998;36(1):26-33.

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.

Continuous Synthesis of Escherichia coli GroEL at a High Temperature: Young Hak Kwak , Kyong Sun Lee , Ji Yeon Kim , Dong Seok Lee , Han Bok Kim; J. Microbiol. 2000;38(3):145-149.

Abstract: GroEL is a typical molecular chaperone. GroEL synthesis patterns at various culture temperatures in Escherichia coli were investigated in this study. No significant differences in the amount of GroEL produced from the chromosome were found at 30 and 37 C. However, GroEL production increased 3.4-fold at 42 C. GroEL synthesis was not transient but continuous at 42 C, although most heat shock gene expression is known to be transient. To understand the role of the groEL structural gene, a groE promoter-lacZ fusion was constructed. Interestingly, while transcriptional fusion is not thermally inducible, it is inducible by ethanol, suggesting that the secondary structure of the groEL transcript is involved in thermal regulation of the groEL gene. Secondary structures of groE mRNA at 37 and 42 C were compared using the computer program RNAdraw. Distinct structures at the two temperatures were found, and these structures may be related to a high level of GroEL expression at 42 C.

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