Involvement of soxRS Regulon in Response of Escherichia coli to Oxidative Stress Induced by Hydrogen Peroxide

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H. Semchyshyn, T. Bagnyukova, and V. Lushchak^*

Department of Biochemistry, Vassyl Stefanyk Precarpathian National University, 76025 Ivano-Frankivsk, Ukraine; fax: +38 (03422) 31-574; E-mail: lushchak@pu.if.ua

^* To whom correspondence should be addressed.

Received September 21, 2004; Revision received November 23, 2004

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The effect of hydrogen peroxide on the activity of soxRS and oxyR regulon enzymes in different strains of Escherichia coli has been studied. Treatment of bacteria with 20 µM H₂O₂ caused an increase in catalase and peroxidase activities (oxyR regulon) in all strains investigated. It is shown for the first time that oxidative stress induced by hydrogen peroxide causes in some E. coli strains a small increase in activity of superoxide dismutase and glucose-6-phosphate dehydrogenase (soxRS regulon). This effect is cancelled by chloramphenicol, an inhibitor of protein synthesis in prokaryotes. The increase in soxRS regulon enzyme activities was not found in the strain lacking the soxR gene. These results provide evidence for the involvement of the soxRS regulon in the adaptive response of E. coli to oxidative stress induced by hydrogen peroxide.

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KEY WORDS: Escherichia coli, hydrogen peroxide, soxRS regulon, superoxide dismutase, glucose-6-phosphate dehydrogenase

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