Growth responses to and accumulation of vanadium in agricultural soil fungi

The aim of this work was to test the growth response of some selected species to toxic metal vanadium, chosen among those isolated from contaminated agricultural soils (organochlorines, potentially toxic elements) in the "Valle Latina" (Lazio, Italy). This area contains high levels of potentially toxic elements due both to human activities and the presence of volcanic rocks (pyroclastic deposits). In particular. vanadium levels exceed the threshold values established by Italian legislation. The soil fungal community was found to be rich in species and we tested the growth responses of six selected species of saprotrophic fungi (Aspergillus terreus, Cladosporium cladosporioides, Clonostachys rosea, Paecilomyces lilacinus, penicillum citrinum, Rhizopus arrhizus). Culture medium (MEA) was amended with ammonium vanadate at concentrations of 1, 2, 3 and 6 mM. Results were based on growth measurements, the tolerance index (TI), scanning electron microscopy (SEM), energy dispersion X-ray microanalysis (EDXA) and the metal concentration in the biomass determined by means of inductively coupled plasma mass spectrometry (ICP-MS). Results revealed a tolerance to vanadium for all the fungi tested at concentrations of up to 6 mM. Tolerance of soil fungi to high natural metal concentrations might be the key factor underlying their tolerance to anthropogenic contamination.