Comparison of the oxidative stress response of two Antarctic fungi to different growth temperatures

Two fungal strains, isolated from Livingston Island, Antarctica (Penicillium commune 161, psychrotolerant and Aspergillus glaucus 363, mesophilic) were investigated for a relationship between growth temperature and oxidative stress response. Cultivation at temperatures below - (10 and 15 degrees C and 10 and 20 degrees C for P. commune and A. glaucus, respectively) and above (25 degrees C and 30 degrees C for P. commune and A. glaucus, respectively) the optimum caused significant difference in growth and glucose uptake in comparison with the control cultures. Enhanced level of reserve carbohydrates (glycogen and trehalose) was determined under cultivation at different temperatures from the optimal one. While the highest content of trehalose was found in the exponential phase, glycogen accumulation was observed in the stationary phase when growth conditions deteriorate. The growth at temperature below- and above-optimum caused strain-dependent changes in two antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT). While SOD activity in the psychrotolerant strain increases with decreasing of growth temperature, the mesophilic A. glaucus demonstrated marked reduction of it at below- and above-optimal temperature. Decreasing trend of CAT activity was observed in both strains below the optimal temperature indicating a lack of antioxidant protection from this enzyme under the cold stress conditions.