Interactions between a soil fungus, Trichoderma harzianum, and IIb metals?adsorption to mycelium and production of complexing metabolites

Abstract

Fungi are capable of accumulating metals and, in soil, such accumulation may influence metal speciation and transport. The interactions between a common soil fungus, Trichoderma harzianum, and IIb elements were studied in the present investigation. The accumulation of the metals zinc, cadmium and mercury by starved and non-starved mycelium at different pH was determined by a batch technique using radioactive tracers; uptake of the metals was found to be large, with respective distribution coefficients of about 103.5, 102.5 and 104.0 for zinc, cadmium and mercury, respectively. Metal accumulation by a starved system was largely independent of pH in the range 3–9, where in a non-starved system an increased accumulation of zinc (at 10−m) was observed at low pH (3–5). Potentiometric titrations performed on the two systems revealed significant differences in acid capacities, i.e. values close to zero for the starved system and 500–800 meq kg− for the non-starved system. The maximum metal uptake was at least 50 mmol kg− at pH 6.5 (calculated from adsorption isotherms). The present findings suggests that in the non-starved system a metabolite is produced and then released when the pH is within a certain range.