Bacterial Weathering of Asbestos

Abstract

The process of bioweathering involving natural microbes, natural plants and transgenic animals has proven to be a very efficient and effective tool for detoxifying xenobiotics. The present investigation uses the same tool as a device for detoxifying asbestos, a potent carcinogenic entity. The cellular mechanism of asbestos toxicity to a certain extent, as shown by research, is attributed to its chemical composition particularly the presence of iron in its structure. Many bacteria release iron chelating compounds, siderophores, which could be instrumental in the study. Treatment of asbestos was carried out under specific parameters with bacterial isolates native to the mines of Rajasthan from which asbestos was collected. An assessment was then done to evaluate reduction in iron content of the asbestos fibres by Scanning Electron Microscopy-Energy Dispersive X-ray (SEM-EDX). A remarkable decrease was observed in the iron content of asbestos following treatment with most of the bacterial isolates used, which probably could form the basis for asbestos bioweathering studies.

Siderophore-mediated iron removal from chrysotile: Implications for asbestos toxicity reduction and bioremediation

“…In the U.S., nearly a thousand sites are either contaminated with asbestos-containing materials or naturally occurring asbestos minerals; many are Brownfield sites that are typically left untreated [5], despite imminent health risks to surrounding communities. As the recommended remediation method—soil capping—is cost prohibitive, the potential for alternative cost-effective remediation strategies, including bioremediation, has been explored [7–13]. However, the bioremediation mechanism and its feasibility in environmental relevant condition is lacking.…”

“…The same processes could also release iron from asbestos and potentially lower its toxicity. Numerous studies demonstrated that bacteria, lichen, and fungi can degrade asbestos [7–9, 11–13, 32, 34, 35] and attributed the degradation to exudates such as organic acids and siderophores. These organic exudates and siderophores can bind ferric and ferrous iron although the exudates have a stronger affinity to ferric iron than ferrous iron [36].…”

Biodeterioration of asbestos cement by siderophore-producing Pseudomonas

“…These isolates are able to produce siderophores and were considered to be potential bioremediators for asbestos, as previously demonstrated for Fusarium oxysporum (Daghino et al, 2005;Martino et al, 2004), Verticillium leptobactrum, and Aspergillus fumigatus (Daghino et al, 2008). Bhattacharya et al (2015) showed a decrease in iron content from asbestos by several Rajasthan mine bacterial isolates identified as Gram-positive and -negative bacteria, with two Gram-positive siderophore producers (Bhattacharya et al, 2016b). Bacterial weathering of asbestos has been recently investigated.…”

A Review of Asbestos Bioweathering by Siderophore-Producing Pseudomonas: A Potential Strategy of Bioremediation

“…Indeed, asbestos is an iron source for various microorganisms. Some studies reported on the one hand, the ability of siderophore-producing organisms to weather asbestos, for example, fungi such as Fusarium oxysporum [81,82], Verticillium leptobactrum, and Aspergillus fumigatus [83], rhizospheric bacteria [14] or Gram-positive bacteria isolates from asbestos mine [13,84]. On the other hand, direct evidence of iron weathering from asbestos by siderophore was shown with deferoxamine [18,85], EDTA [78,85] or citrate [85].…”

“…Indeed, organisms have been isolated from various serpentine sites. Bacteria isolated from asbestos rocks or soil from several Indian mines decrease the iron content of asbestos [13]. Rhizosphere bacteria contribute also to the weathering process in serpentine soil [14].…”