The role of antioxidant systems in the cold stress response of Escherichia coli

The response of aerobically grown Escherichia coli cells to the cold shock induced by the rapid lowering of growth temperature from 37 to 20 degreesC was found to be basically the same as the oxidative stress response. The enhanced sensitivity of cells deficient in two superoxide dismutases, Mn-SOD and Fe-SOD, and the increased expression of the Mn-SOD gene, sodA, in response to cold stress were interpreted as both oxidative and cold stresses are due to a rise in the intracellular level of superoxide anion. The long-term cultivation of E. coli at 20 degreesC was also accompanied by the typical oxidative stress response reactions-an enhanced expression of the Mn-SOD and catalase HPI genes and a decrease in the intracellular level of reduced glutathione (GSH) and in the GSH/GSSG ratio.