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

Our plain-English summary of A Review of Asbestos Bioweathering by Siderophore-Producing Pseudomonas: A Potential Strategy of Bioremediation, by S.R. David, V.A. Geoffroy (Microorganisms, 2020).

The study

• Authors: S.R. David, V.A. Geoffroy
• Journal: Microorganisms
• Published: 2020;8(12)
• Type of article: Review
• Cited by: 10 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Asbestos, silicate minerals present in soil and used for building constructions for many years, are highly toxic due primarily to the presence of high concentrations of the transition metal iron. Microbial weathering of asbestos occurs through various alteration mechanisms. Siderophores, complex agents specialized in metal chelation, are common mechanisms described in mineral alteration. Solubilized metals from the fiber can serve as micronutrients for telluric microorganisms. The review focuses on the bioweathering of asbestos fibers, found in soil or manufactured by humans with gypsum (asbestos flocking) or cement, by siderophore-producing Pseudomonas. A better understanding of the interactions between asbestos and bacteria will give a perspective of a detoxification process inhibiting asbestos toxicity.

In plain English

This article is a review, not a new study. The authors reviewed laboratory research on how soil bacteria called Pseudomonas weather asbestos fibers, mainly chrysotile, by removing iron. The bacteria do this using siderophores, molecules they make to capture iron. Much of the work described is the authors' own earlier laboratory research. It used raw chrysotile and two asbestos-containing wastes: asbestos flocking (about 90% free fibers and 10% gypsum) and asbestos cement (about 10% fibers in 90% cement). Iron dissolution was reduced without both siderophores, pyoverdine and pyochelin: for raw chrysotile, using culture fluid from a strain lacking both; for the wastes, using that strain itself. Ten pyoverdines were tested. Those from P. mandelii and P. syringae removed iron more efficiently from flocking and from cement, respectively. Long-term pyoverdine treatment greatly lowered the fibers' iron content, which the authors said probably leads to lower fiber toxicity. The authors concluded that the deterioration of asbestos waste by these bacteria appears to be a promising process. They noted other mechanisms may be involved and biofilms have not been clearly investigated.

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: Review of published laboratory research, largely the authors' own earlier studies (figures adapted from David et al.)
• Who was studied: No people were studied. The review covers laboratory studies of Pseudomonas bacteria (mainly Pseudomonas aeruginosa PAO1 and mutants unable to make its siderophores) and their siderophores, tested with raw chrysotile and asbestos-containing waste. Most of these studies were by the authors' own group (David et al.).
• Exposure: Chrysotile fibers in raw asbestos and in two asbestos-containing wastes: asbestos cement (about 10% asbestos fibers in 90% cement) and asbestos flocking (about 90% free asbestos fibers and 10% gypsum)
• Main results:
  • With ground raw chrysotile, tested with purified pyoverdine or culture supernatants (culture fluid) from Pseudomonas aeruginosa PAO1 and its siderophore-deficient strains, an earlier study by the authors' group found that the absence of both siderophores (pyoverdine and pyochelin) had a significant impact on iron dissolution.
  • With asbestos cement and asbestos flocking waste, inoculated with the bacterial strains themselves, the absence of both siderophores greatly reduced iron dissolution. The role of each siderophore depended on the waste: in flocking, one siderophore compensated for the absence of the other; in cement, losing either one affected iron removal, with a stronger effect when pyochelin was absent.
  • Of 10 pyoverdines tested, pyoverdine-containing supernatants from P. mandelii were more efficient at removing iron from asbestos flocking, and those from P. syringae were more efficient for asbestos cement.
  • Long-term treatment of asbestos waste with pyoverdines led to a large decrease in the iron content of the asbestos fibers. The authors said this probably leads to lower fiber toxicity.
• The authors' conclusion: The authors concluded that biodeterioration of asbestos-containing waste by siderophore-producing Pseudomonas appears to be a promising process.
• Limitations the authors state:
  • Mechanisms other than siderophores, such as organic acids, biofilm or redox processes, may also be involved in asbestos alteration.
  • The role of biofilm has not yet been clearly investigated.
  • How specifically each pyoverdine binds iron and other metals is not yet known.

Topics

Medical terms in this study, explained in our Lexicon: Silicate.

Related studies

• Iron removal from raw asbestos by siderophores-producing Pseudomonas — S.R. David, D. Ihiawakrim, et al. (2020)
• Biodeterioration of asbestos cement by siderophore-producing Pseudomonas — S.R. David, A. Jaouen, et al. (2021)
• Engineering siderophore production in Pseudomonas to improve asbestos weathering — M. Lemare, H. Puja, et al. (2022)
• Siderophore-mediated iron removal from chrysotile: Implications for asbestos toxicity reduction and bioremediation — S.K. Mohanty, C. Gonneau, et al. (2018)
• Flocking asbestos waste, an iron and magnesium source for Pseudomonas — S.R. David, S. Fritsch, et al. (2020)
• Recent Advances of Immune Checkpoint Inhibition and Potential for (Combined) TIGIT Blockade as a New Strategy for Malignant Pleural Mesothelioma — S. Rovers, A. Janssens, et al. (2022)

Browse return to medical research.