Biosorption and bioaccumulation of thallium by thallium-tolerant fungal isolates

Thallium (Tl) contamination in soil exerts a significant threat to the ecosystem health due to its high toxicity. However, little is known about the effect of Tl on the microbial community in soil. The present study aimed at... [ view full abstract ]

Thallium (Tl) contamination in soil exerts a significant threat to the ecosystem health due to its high toxicity. However, little is known about the effect of Tl on the microbial community in soil. The present study aimed at characterizing the culturable microbial groups in long-term Tl-polluted soils. The soils at the study site were highly contaminated with Tl derived from Tl-rich sulfide mineralization and mining activity in Guizhou Province, Southwest China. Our investigation clearly showed the existence of culturable bacteria, filamentous fungi and actinomyces in long-term Tl-contaminated soils. Indeed, some fungal groups can grow in the presence of high Tl level up to 1,000 mg kg-1. We have isolated and identified nine Tl-tolerant fungal strains based on the morphological traits and ITS analysis. The dominant genera identified were Trichoderma, Penicillium and Paecilomyces. Preliminary data showed a positive correlation between the biomass and the biosorbed Tl content. The Tl-tolerant strains were capable of bioaccumulating Tl, up to 7,189 mg kg-1 dry weight. The subcellular distribution of Tl showed obvious compartmentalization: cytoplasm >> cell wall > organelle. The majority of Tl (up to 79%) was found in the cytoplasm, suggesting that intracellular compartmentalization appeared to be responsible for detoxification. These findings further suggest the applicability of the fungal isolates for cleanup of Tl in Tl-polluted water and soil.