Bioweathering of chrysotile by fungi isolated in ophiolitic sites

Abstract

Asbestos minerals are commonly found in serpentine rocks and because of the hazard to human health, research has recently focused on possible detoxification strategies. Some fungal species that inhabit serpentine sites (two disused chrysotile asbestos mines in the Western Alps) have been isolated and characterized in order to obtain data on their biodiversity and bioweathering abilities on chrysotile fibres. The three dominant species (Verticillium leptobactrum, Paecilomyces lilacinus and Aspergillus fumigatus) have proved to be able to actively remove iron from chrysotile fibres, V. leptobactrum being the most efficient. A wide range of serpentinicolous fungi release siderophores, iron-chelating compounds, that could play a role in iron extraction from fibres. Iron removal had been correlated previously with a decrease in the toxic potential of fibres, and a biotechnological application of fungi can be envisaged for asbestos detoxification.

Bacterial Weathering of Asbestos

“…Asbestos minerals although highly resistant to weathering, have been reported to be biodegraded by certain fungal species like Verticellum leptobactrum, Paecilomyces lilacinus and Aspergillus fumigatus. This weathering was either by extraction of iron from asbestos by siderophores or by disruption of the magnesium-silicate framework of asbestos [9]. As evident from the results of the present investigation, four of the bacterial isolates were identified as showing a considerable decrease in the iron content of asbestos, after treatment.…”

“…As evident from the results of the present investigation, four of the bacterial isolates were identified as showing a considerable decrease in the iron content of asbestos, after treatment. The probable reason for this, although yet to be investigated, could be the production of siderophores by these bacterial species, similar to that reported for asbestos bioremediation by fungal strains [9]. None of the bacterial species worked with could disrupt the magnesium-silicate framework of asbestos as a feature of bioremediation, as reported for fungal weathering of asbestos in some cases.…”

“…The damaging effect on naked DNA in in vitro situations was reduced by removal of iron from asbestos, by fungi belonging to Verticillium species, Paecilomyces species and Fusarium oysporium [4]. Aspergillus fumigatus was also shown to be a potent bioremediator of asbestos [9]. The removal of magnesium from the fibres both in situ and in vitro by lichen forming fungus Xanthoparmelia tinctina growing in close proximity to asbestos in serpentine rocks was reported [13,14].…”

“…Although most organisms find it difficult to grow in contaminated soil, some microbes due to their inherent genetic makeup are able to grow, survive and degrade the recalcitrant compounds. Bioremediation as a probable answer to asbestos toxicity has been used in the recent past [9][10][11].…”

Lichen deterioration of asbestos and asbestiform minerals of serpentinite rocks in Western Alps

“…In fact many studies have reported on asbestiform minerals not commercially exploited, but sharing a fibrous habit with asbestos, whose pathogenicity is mostly unknown (Baris et al, 1987;Comba et al, 2003;McDonald et al, 2004;Turci et al, 2009;Pugnaloni et al, 2010); NOA are more than likely to appear in polymineralic veins, including other fibrous minerals (Groppo and Compagnoni, 2007a); (c) opposite to airborne fibres generated by human activities, naturally released fibres from serpentinite outcrops have been often affected by abiotic and biotic environmental forces for a long time, which may have modified their toxicity related physico chemical features (Favero Longo et al, 2005a, 2009aDaghino et al, 2008).…”