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Adaptive Response of Humicola Lutea to Copper Exposure

ABSTRACT In the present study, we examined the adaptive response of the filamentous fungus Humicola lutea 103 to copper stress. Our findings indicate that pretreatment with low concentrations of copper ions led to the development of resistance to high concentrations of the same heavy metal. Spores subjected to 40 μg/ml Cu++ showed higher resistance to killing by subsequent incubation in 70 or 150 μg/ml Cu++ compared to the single treatment. Pre-exposure strategy also caused a higher amount of biomass accumulation and recovery of the fungal growth curves to the control curves shape. Moreover, this strategy exerted protective effect against the oxidative damaged proteins in H. lutea cells, which was accompanied by a corresponding accumulation of reserve carbohydrates such as trehalose and glycogen. Adaptive cell response included induction in the activity of the first antioxidative enzyme superoxide dismutase, but catalase activity was independent of copper treatment and pretreatment. Therefore, we concluded that the pre-exposure to mild copper stress induces a coordinated response that decreases the oxidative stress degree in H. lutea cells when this pre-exposure was followed by severe stress.