Abstract

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.

摘要

重金属污染的土壤是对金属毒性表现出高度耐受性的真菌的主要来源。这些真菌使用各种防御机制在极端条件下生存。但是，关于抗氧化反应在真菌对不同浓度金属离子混合物的耐受性中的作用知之甚少。本研究的目的是比较两种烟曲霉的细胞反应从严重污染的土壤中分离出来的菌株，可以抵抗多金属（Cd、Cu、Ni 和 Zn 离子）处理。两种菌株都表现出对增加浓度的多金属系统的高度耐受性。数据证实了氧化应激和重金属毒性之间的关系。用多金属混合物处理以剂量依赖性方式降低真菌生长、葡萄糖摄取和细胞外蛋白质合成。不同浓度的重金属离子的组合导致羰基化受损蛋白质水平的增加以及糖原和海藻糖含量的变化。我们的结果显示了抗氧化酶的独特特征。虽然 SOD 活性受到含金属溶液的刺激，但 CAT 活性趋于降低。两种菌株之间的比较表明，烟曲霉由于更积极的抗氧化防御，随着多金属系统浓度的增加，G 表现出比烟曲霉3-2更高的耐受性。