Fungal weathering and implications in the solubilization of metals from soil and from asbestos fibres

Geomycology investigates the impact of fungi on geological processes, including the alteration and weathering of rocks and minerals, mediated both by biomechanical and by biochemical activities. Several functional groups of fungi are involved in mineral bioweathering, including saprotrophic and mycorrhizal fungi. Serpentine sites provide interesting environmental cases for geomycology, because they are naturally enriched in heavy metals and can bear asbestos-rich rocks. An otherwise uncommon species, Verticillium leptobactrum, was found to be abundant in several serpentine sites in the Western Alps. V. leptobactrum and other fungal strains were shown to be able to extract different amounts of iron and magnesium from asbestos in vitro. The amount of iron mobilized from the fibres depended on the fungal activity but also on the physical characteristics of the mineral. Iron is of particular importance because one of the reactions determining asbestos toxicity is the iron-catalyzed generation of free radicals leading to biomolecules oxidation. Asbestos fibres modified in vitro by fungi were less chemically reactive and lost their oxidative activity against DNA.