Physical and biochemical interactions of soil fungi with asbestos fibers

Iron, a structural component of most asbestos, is thought to play a crucial role in asbestos toxicity. Surface iron favors fiber uptake by mammalian cells and promotes the generation of free radicals with consequent DNA and lipid damage. In some cases, chemical removal of iron from asbestos fibers has reduced several cellular responses to asbestos. Since iron represents an essential element for soil microorganisms, many of them have developed mechanisms to scavenge this element from poorly soluble forms. We have investigated the ability of some soil fungi to produce iron chelators capable of extracting iron from crocidolite (blue asbestos). Many of the species/isolates investigated could remove significant amounts of iron from crocidolite fibers, Fusarium oxysporum being the most effective. The fungal responses following exposure to asbestos fibers also have been investigated with morphological and biochemical approaches. In liquid cultures, the fibers were visibly cleared from the suspension because they were tightly bound to the fungal hyphae. Modifications in the fungal protein profiles were observed following exposure to asbestos fibers. By binding the fibers and depriving them of iron, selected species/strains of soil fungi might represent interesting tools for the bioremediation of asbestos-contaminated soils.