Potential in mycoremediation of soil saprotrophic fungi: arsenic uptake and tolerance in different nutritional conditions

Arsenic (As) is a metalloid, naturally occurring in the earth crust. Anthropogenic sources, such as processing of arsenic-bearing minerals, are mainly responsible for environmental contamination, arising concern for toxic effects of As on human health and ecosystems. Fungi play key roles in fundamental biogeochemical cycles of essential and toxic elements and soil formation. Several studies reported that fungi can tolerate and accumulate high concentrations of arsenic and mediate processes of biovolatilisation through methylation. Our research aimed to evaluate As tolerance and bioaccumulation of four species of soil saprotrophic fungi and how nutritional conditions influence them. Absidia spinosa, Purpureocillium lilacinum, Metarhizium marquandii and Cephalotrichum nanum, previously isolated from areas with high natural As concentrations, were tested in two cultural media (MEA and Czapek-Dox). Results revealed high tolerance to all tested As concentrations (10, 20 and 50 mg/L sodium arsenite). Growth responses and tolerance to As have been investigated by tolerance indices (Rt:Rc (%) and T.I. (%)), based on growth data (diametric extension and dry weight). Most of these species resulted tolerant to all tested As concentrations, with growth responses also varying according to cultural media. pH medium after fungal growth was measured to study pH variation and metabolic responses. Chemical analyses by HG-AFS revealed As bioaccumulation. Elemental chemical composition of fungal biomass for all tested species was determined by ICP-MS and ICP-AES to assess how As occurrence and fungal responses to it influence the elements’ uptake. Results shed further light on fungal geoactive roles in the environmental fate of As and provide potential applications in bioremediation.