[Hydrogen peroxide modulates intracellular levels of thiols and potassium in Escherichia coli cells].

Exposure of growing Escherichia coli K12 cells to 2.0-11.0 mM H2O2 resulted in an increase in the intracellular level of low-molecular-weight thiols (LMWT), whereas exposure to 25 mM H2O2 resulted in its decrease. An inverse correlation between levels of LMWT and potassium was revealed. The treatment of E. coli delta oxyR cells, which are incapable of the adaptive response to H2O2, with 10 mM H2O2 caused a decrease in the LMWT level. In E. coli oxyR2 cells, which constitutively express oxyR-controlled proteins, the same treatment caused a 20% increase in the LMWT level. In response to treatment with the oxidant, delta oxyR mutants lost two times more potassium than wild-type cells (oxyR+). A time course study of the levels of LMWT and potassium in mutants with an affected katG gene, which encodes the HPI catalase and is under the control of oxyR, showed that oxyR may regulate LMWT and potassium levels indirectly, through the regulation of catalase activity. A relationship between catalase activity and the LMWT level was revealed in hydrogen peroxide-treated E. coli cells.