Cadmium and zinc response of the fungi Heliscus lugdunensis and Verticillium cf. alboatrum isolated from highly polluted water

The aquatic hyphomycete Heliscus lugdunensis and the terrestrial fungus Verticillium cf. alboatrum, both isolated from a highly polluted surface water, were investigated for their tolerance against Cd and Zn. Hl-H4 showed a 50% growth inhibition at 0.1 mM Cd, whereas at 0.7 mM Cd the growth of Va-H4 was only reduced by 30%. The fungi also showed a remarkable difference in their Zn-tolerance. The growth of Va-H4 was not inhibited at 1 mM Zn, whereas for Hl-H4 no growth occurred above 0.3 mM Zn. The biosorption and accumulation capacities for Cd or Zn of both fungi differed between the fungal species. In a 0.1 mM Cd-medium Hl-H4 biosorbed 15-fold and accumulated 39-fold more Cd than Va-H4. Exposure to 0.3 mM Zn resulted in a 13-fold higher biosorption and 11-fold higher accumulation for Hl-H4 than Va-H4. As glutathione (GSH) is known to be involved in the phytochelatin synthesis and other stress related processes we investigated its synthesis. Both fungi increased their synthesis of GSH in response to Cd. For Hl-H4 a concentration of 0.0125 mM Cd, corresponding to an intracellular Cd content of 2.1 nmol Cd mg-1 dw, increased the GSH content, whereas Va-H4 only responded with a higher production of GSH at 1 mM Cd and a concomitant intracellular Cd content of 22.5 nmol Cd mg-1 dw. An increased GSH synthesis under Zn-stress was only detectable for Va-H4 (20 mM)