Fungal weathering of asbestos in semi arid regions of India

Our plain-English summary of Fungal weathering of asbestos in semi arid regions of India, by S. Bhattacharya, P.J. John, L. Ledwani (Ecotoxicology and Environmental Safety, 2016).

The study

• Authors: S. Bhattacharya, P.J. John, L. Ledwani
• Journal: Ecotoxicology and Environmental Safety
• Published: 2016;124:186-192
• Cited by: 7 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The science of Geomicrobiology, which deals with mineral- microbe interaction in nature contributes effectively to three important processes namely- mineral and metal bioremediation, biomining and soil mineral formation by microbes. Bioremediation one of the important process of the above, degrades or transforms hazardous contaminants to less toxic compounds. Several groups of fungi have proved highly efficient in this aspect, with asbestos being one such toxic entity in the environment on which their activity was studied. The present investigation uses the same tool as a device for detoxifying asbestos, a potent carcinogenic entity; with fungal isolates native to the asbestos mines of Rajasthan, India, being investigated for the first time. The cellular mechanism of asbestos toxicity is mainly attributed to the presence of iron in its chemical composition which catalyzes generation of free radicals leading to oxidation of biomolecules. The two dominant novel species found therein, identified as Aspergillus tubingenesis and Coemansia reversa have proved capable of actively removing iron from asbestos fibers as studied by scanning electron microscopy- electron diffraction X-ray (SEM-EDX) analysis. This probably could lead to a reduction in toxicity of asbestos, due to reduced iron concentration as reported in related studies. Many fungi are known to release iron chelating compounds, siderophores, which could be instrumental in the study. The findings related to two new fungal species being added to the list of earlier identified fungal bioremediators of asbestos, widens the prospect of using bioremediation as an effective tool for asbestos detoxification.

Copyright © 2015 Elsevier Inc. All rights reserved.

In plain English

In this laboratory study, the authors grew fungi from asbestos rock and asbestos-contaminated soil collected at four abandoned asbestos mines in Rajasthan, India: two in Rajsamand district and two in Jodhpur district. Six dominant fungal isolates were each incubated for 20 days with processed asbestos fibers from an asbestos-cement manufacturer in Jaipur. The elements in the fibers were then measured by SEM-EDX and compared with fibers incubated without fungi. The control fibers contained 6.86% iron by weight. Two isolates, identified as Aspergillus tubingensis and Coemansia reversa, reduced iron content by 16.6% and 31.2% respectively, which the authors reported as statistically significant. The iron-to-silicon ratio fell from 0.285 to 0.21 and 0.16. The other four isolates did not show a comparable result, and magnesium and silicon did not change significantly. Both species tested positive for siderophores, which are iron-binding compounds. Citing related studies, the authors concluded that this iron removal probably could lead to reduced asbestos toxicity. They noted a small sample size because access to the mines was restricted.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Laboratory (in vitro) experiment: fungi isolated from mine samples were incubated with asbestos fibers, and the fibers were analyzed by SEM-EDX
• Who was studied: Fungi isolated from asbestos rock and asbestos-contaminated soil at four abandoned asbestos mines in Rajasthan, India (two in Rajsamand district, two in Jodhpur district). Six isolates were tested, the most dominant one from each of six samples (four rock, two soil).
• Exposure: Processed asbestos fibers (fiber type not stated) from an asbestos-cement product manufacturer in Jaipur, incubated with each fungal isolate for 20 days at 25 °C and pH 5.5; control fibers were incubated under identical conditions without fungi
• Main results:
  • Untreated processed asbestos fibers contained 6.86% iron of total elemental composition
  • Compared with control, iron content of treated asbestos was reduced by 16.6% with isolate J1F and 31.2% with isolate J2F (iron weight % 5.72 and 4.72 versus 6.86 in control)
  • The iron weight % differences for J1F and J2F versus control were reported as statistically significant (p less than 0.05, one-way ANOVA)
  • Iron-to-silicon (Fe/Si) ratio was 0.285 for fibers in medium alone, 0.21 with Aspergillus tubingenesis and 0.16 with Coemansia reversa
  • The other four isolates did not show a comparable reduction in iron
  • The authors suggested that the increased iron content seen in some samples, mainly UR1F and US1F, could possibly be due to absence of siderophores
  • No significant change in magnesium or silicon weight % after fungal treatment
  • SEM imaging showed no significant structural difference between control and fungus-treated fibers
  • By gene sequencing, isolate J1F was identified as Aspergillus tubingensis and isolate J2F as Coemansia reversa
  • Both identified species gave a positive color change in the CAS agar siderophore test, consistent across all replicates
• The authors' conclusion: The authors concluded that the fungal removal of iron from asbestos probably could lead to reduced asbestos toxicity, based on related studies, and that the two species widen the prospect of bioremediation for asbestos detoxification
• Limitations the authors state:
  • Small sample size, because access to the officially banned mines was restricted

Topics

Medical terms in this study, explained in our Lexicon: Carcinogenic, Scanning Electron Microscopy (SEM).

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