Comparison of the Oxidative Stress Response of Two Aspergillus fumigatus Strains Isolated from Polluted Soils against Combined Heavy Metal Toxicity

Heavy metal polluted soils are major sources of fungi exhibiting high tolerance toward metal toxicity. These fungi use various defense mechanisms to survive under extreme conditions. But, a little is known about the role of antioxidant response in the fungal tolerance to varied concentrations of mixture of metal ions. The aim of present study was to compare the cell response of two Aspergillus fumigatus strains, isolated from heavily polluted soils, against multi-metal (Cd, Cu, Ni, and Zn ions) treatment. Both strains demonstrated high tolerance to increasing concentrations of multi-metal systems. The data confirmed a relationship between oxidative stress and heavy metal toxicity. The treatment with multi-metal mixture declined fungal growth, glucose uptake and extracellular protein synthesis in a dose-dependent manner. Combination of heavy metal ions in diverse concentrations induced an increase in the levels of carbonylated-damaged proteins and changes in glycogen and trehalose content. Our results showed a distinct profile of antioxidant enzymes. While the SOD activity was stimulated by metal containing solutions, CAT activity tended to decrease. Comparison between both strains revealed that A. fumigatus G showed higher tolerance than A. fumigatus 3-2 with increasing concentrations of multi-metal systems due to more active antioxidant defence.