Enhanced resistance to peroxide stress in Escherichia coli grown outside their niche temperatures

摘要

Extended exposure of Escherichia coli to temperatures above and below their growth optimum led to significant changes in oxidant production and antioxidant defense. At 20 deg C an increase in the intracellular H_2O_2 concentration and oxidized glutathione (GSSG) level was observed against a background of low levels of reduced glutathione (GSH) and decreased catalase and glutathione reductase (GOR) activities. The intracellular H_2O_2 and GSSG concentrations had minimal values at 30 and 37 deg C, butrose again at 42 deg C, suggesting that oxidative processes were intensified at high temperatures. An increase in temperature from 20 to 42 deg C led to an elevation in the oxygen respiration rate and superoxide production; a 5-fold increase in the intracellular GSH concentration and in the GSH:GSSG ratio occurred simultaneously. Catalase HPI and GOR activities were elevated 4.4- and 1.5-fold, respectively. Prolonged exposure to sublethal temperatures facilitated an adaptation to subsequent oxidative stress produced by the addition of H_2O_2.