The response of to oxidative stresses has been examined. On challenging for 60 min at early exponential phase with either 40 mM HO or 6 mM menadione (MD), a superoxide-generating agent, less than 10% of the cells survived. Pretreating cells with 0.2 mM HO or 0.2 mM MD for 1 h significantly increased survival of these lethal doses of each oxidant, indicating the existence of an adaptive response to oxidative stress. Furthermore, cells pretreated with a low dose of MD became resistant to a lethal dose of HO. However, cells pretreated with HO became only partially resistant to a lethal dose of MD. Adaptation was accompanied by the induction of several oxidative defence enzymes. The presence of 0/2 mM HO induced catalase by 2.8-fold and peroxidase by 2.0-fold. The presence of 0.2 mM MD induced catalase by 2.0-fold, glucose-6-phosphate dehydrogenase by 1.9-fold, glutathione reductase by 2.7-fold, peroxidase by 3.0-fold, and superoxide dismutase (SOD) by 2.1-fold. The higher induction of these defence enzymes by MD may explain why MD-pretreated cells were better adapted to lethal doses of oxidants than HO-pretreated ones. All these enzymes except SOD and peroxidase increased more than 5.0-fold as cells proceeded into stationary phase. The GSH/GSSG ratio also increased by 60%. These changes accord with the observation that stationary phase cells survive oxidant treatment better than cells in vegetative growth.


Article metrics loading...

Loading full text...

Full text loading...


Most cited this month

This is a required field
Please enter a valid email address
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error