Cellular Response to Cu‐ and Zn‐Induced Oxidative Stress in Aspergillus fumigatus Isolated From Polluted Soils in Bulgaria

Abstract

The fungal strain Aspergillus fumigatus 32 isolated from the tailings pond at the copper mine “Vlaykov vruh,” Bulgaria, showed high tolerance to Cu2+ and Zn2+. This study was designed to explore the relationship between Cu2+ and Zn2+ tolerance and cellular response to oxidative stress. The model strain was identified to species level by morphological and molecular methods. Fungal cultures were exposed to enhanced concentrations of metal ions. The effect of Cu2+ and Zn2+ was evaluated by the changes in fungal growth and morphology, the level of oxidative stress biomarkers, and the antioxidant activities of enzymes such as superoxide dismutase (SOD) and catalase (CAT). Two different cellular responses occurred: The concentrations of up to 500 μg/mL caused enhanced levels of oxidative stress biomarkers (glycogen and trehalose accumulation and oxidatively damaged protein content), as well as an increase in SOD and CAT activities. The treatment with concentrations from 500 to 2000 μg/mL led to enhanced glycogen consumption, accelerated proteolysis, and a decrease in SOD and CAT activities. The present results provide additional information about the participation of oxidative stress and antioxidant defense in enhanced tolerance of fungi isolated from metal‐polluted soils. Probably, survival at extremely high concentrations also requires the participation of other defense mechanisms. Furthermore, the enhanced understanding of these processes will provide essential tools for efficient remediation practices.