Еffect of Cadmium Ions on the Fungal Strain Aspergillus fumigatus 32 Isolated from Metal Polluted Soil

The fungal strain Aspergillus fumigatus 32 was isolated from metal polluted soil (around the tailing Vlajkov vrah, Bulgaria). Effect of enhanced concentrations of cadmium ions (redox-inactive metal) on the growth and morphology, as well as the participation of oxidative stress in cadmium-induced toxicity, was reported. A. fumigatus demonstrated a high tolerance to cadmium, exhibiting remarkable growth in liquid and agar media. High metal concentrations affected fungal morphology and caused oxidative stress events such as changes in the level of reserve carbohydrates and oxidative damaged proteins. A sharp increase in trehalose content and accelerated consumption of glycogen in the presence of cadmium ions at concentration above 5 µg/ml were detected. In addition, a decrease in carbonylated proteins was measured, particularly pronounced at high concentrations (70 and 100 µg/ml). Cadmium ions exposure with 5, 20, and 50 µg/ml resulted in enhanced superoxide dismutase (SOD) level, but the higher concentrations (70 and 100 µg/ml) significantly inhibited this activity. Continuous decrease was also observed for catalase (CAT) activity. Probably, at higher concentrations of cadmium ions antioxidant enzymatic defence does not seem to be a major mechanism of cadmium tolerance in the strain A. fumigatus.