Comparative study of heavy metal-induced oxidative stress responses in Schizophyllum commune Fr. and Cyathus striatus Willd.

Heavy metal exposure causes reactive oxygen species generation and oxidative stress in nearly all aerobic organisms. Antioxidant enzymes with free radical scavenging properties counter this oxidative stress produced by heavy metals. In this study, the effects of heavy metal-induced oxidative stress on the activities of antioxidant enzymes, including catalase, peroxidase, and superoxide dismutase, have been evaluated in two selected lignicolous fungal strains, Schizophyllum commune Fr. and Cyathus striatus Willd. The results showed that heavy metals exert toxicity in both fungal strains by affecting the oxidative metabolism, as evidenced by increased production of hydrogen peroxide. An increase in malonaldehyde concentration was observed at a concentration of 100 mg/L of metal ions, indicating that heavy metal exposure causes oxidative damage. To counter the oxidative stress, the activities of antioxidant enzymes, including catalase, peroxidase, and superoxide dismutase, were increased upon exposure to metal ion concentrations. However, a decrease in antioxidant enzyme activity was observed with a further increase in metal ion concentration, which indicates reactive oxygen species-induced oxidative stress. Furthermore, reduced glutathione also plays an important role in the detoxification of heavy metal ions at lower concentrations. Thus, this work suggests that these wood-rot fungi, S. commune and C. striatus, may have the potential to tolerate and accumulate heavy metals by the effective antioxidant defence mechanism, where catalase, peroxidase, superoxide dismutase, and glutathione may play a significant role in this resistance.