Microbe-Mineral Interactions between Asbestos and Thermophilic Chemolithoautotrophic Anaerobes

Our plain-English summary of Microbe-Mineral Interactions between Asbestos and Thermophilic Chemolithoautotrophic Anaerobes, by J.K. Choi, R. Vigliaturo, R. Gieré, et al (Applied and Environmental Microbiology, 2023).

The study

• Authors: J.K. Choi, R. Vigliaturo, R. Gieré, I. Pérez-Rodríguez
• Journal: Applied and Environmental Microbiology
• Published: 2023;89(6):e0204822
• Cited by: 3 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

The Fe content and the morphometry of asbestos are two major factors linked to its toxicity. This study explored the use of microbe-mineral interactions between asbestos (and asbestos-like) minerals and thermophilic chemolithoautotrophic microorganisms as possible mineral dissolution treatments targeting their toxic properties. The removal of Fe from crocidolite was tested through chemolithoautotrophic Fe(III) reduction activities at 60°C. Chrysotile and tremolite-actinolite were tested for dissolution and potential release of elements like Si and Mg through biosilicification processes at 75°C. Our results show that chemolithoautotrophic Fe(III) reduction activities by Deferrisoma palaeochoriense were supported with crocidolite as the sole source of Fe(III) used as a terminal electron acceptor during respiration. Microbial Fe(III) reduction activities resulted in higher Fe release rates from crocidolite in comparison to previous studies on Fe leaching from crocidolite through Fe assimilation activities by soil fungi. Evidence of biosilicification in Thermovibrio ammonificans did not correspond with increased Si and Mg release from chrysotile or tremolite-actinolite dissolution. However, overall Si and Mg release from chrysotile into our experimental medium outmatched previously reported capabilities for Si and Mg release from chrysotile by fungi. Differences in the profiles of elements released from chrysotile and tremolite-actinolite during microbe-mineral experiments with T. ammonificans underscored the relevance of underlying crystallochemical differences in driving mineral dissolution and elemental bioavailability. Experimental studies targeting the interactions between chemolithoautotrophs and asbestos (or asbestos-like) minerals offer new access to the mechanisms behind crystallochemical mineral alterations and their role in the development of tailored asbestos treatments. IMPORTANCE We explored the potential of chemosynthetic microorganisms growing at high temperatures to induce the release of key elements (mainly iron, silicon, and magnesium) involved in the known toxic properties (iron content and fibrous mineral shapes) of asbestos minerals. We show for the first time that the microbial respiration of iron from amphibole asbestos releases some of the iron contained in the mineral while supporting microbial growth. Another microorganism imposed on the two main types of asbestos minerals (serpentines and amphiboles) resulted in distinct elemental release profiles for each type of asbestos during mineral dissolution. Despite evidence of microbially mediated dissolution in all minerals, none of the microorganisms tested disrupted the structure of the asbestos mineral fibers. Further constraints on the relationships between elemental release rates, amount of starting asbestos, reaction volumes, and incubation times will be required to better compare asbestos dissolution treatments studied to date.

In plain English

This laboratory experiment tested whether two heat-loving bacteria grown without oxygen could remove toxicity-linked elements from asbestos minerals. Deferrisoma palaeochoriense was grown at 60°C with UICC crocidolite as its only source of Fe(III), used for respiration. Thermovibrio ammonificans was grown at 75°C with chrysotile or tremolite-actinolite. Experiments ran one week in triplicate, alongside minerals in medium alone. D. palaeochoriense grew, and the Fe(II) share of total extractable iron in unfiltered culture samples rose from 25.2% to 54.4%. Dissolved iron reached about 0.14 mM after 2 days, a release rate of about 0.006 mM per gram per day. That rate exceeded the rates the authors compiled for soil fungi but was below two non-biological treatments reported elsewhere. With chrysotile, T. ammonificans showed signs of silicon collecting on its cells (biosilicification). However, it did not increase silicon or magnesium release from chrysotile beyond medium alone. All three minerals kept their crystallinity; chrysotile and tremolite-actinolite showed minor surface dissolution. The authors concluded that iron respiration outperformed fungal iron uptake for removing iron from crocidolite, and that comparing treatments needs further work.

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 experiment growing microorganisms with asbestos minerals (no humans or animals), with mineral-free microbial controls and mineral-only controls
• Who was studied: Two thermophilic, chemolithoautotrophic anaerobic bacteria: Deferrisoma palaeochoriense (tested with crocidolite at 60°C) and Thermovibrio ammonificans (tested with chrysotile and tremolite-actinolite at 75°C). Cultures were in 25 mL of medium, in triplicate, for 1 week.
• Exposure: Minerals tested: UICC reference crocidolite at 10 g per litre as the sole source of Fe(III), used as the terminal electron acceptor for respiration. Chrysotile and tremolite-actinolite at 1 g per litre, tested for silicon and magnesium release through bacterial biosilicification.
• Main results:
  • D. palaeochoriense grew with crocidolite as its only source of Fe(III), used as the terminal electron acceptor. Its doubling time with crocidolite was 10.1 hours, slightly slower than with the iron hydroxide control.
  • Crocidolite-containing cultures were measured by acid digestion of unfiltered culture samples. In these cultures, Fe(II) as a percentage of total extractable iron rose from 25.2% at 0 hours to 54.4% at 171 hours.
  • In crocidolite cultures with D. palaeochoriense, dissolved iron reached about 0.14 mM after 2 days, and then decreased with longer incubation.
  • The microbial iron release rate from crocidolite was about 0.006 mM per gram per day during the first 48 hours. This was higher than rates compiled from earlier fungal studies. It was lower than earlier non-biological incubations in saline with sodium ascorbate and in simulated alveolar lung fluid.
  • Chrysotile released the same levels of silicon and magnesium with or without T. ammonificans, despite evidence of biosilicification. Dissolved silicon in chrysotile cultures was 1.1 mM.
  • Tremolite-actinolite released less silicon than chrysotile, both in cultures and in medium alone. No biosilicification was seen in T. ammonificans grown with tremolite-actinolite.
  • Crocidolite's bulk crystallinity did not change over time despite the microbial iron reduction.
  • Chrysotile and tremolite-actinolite kept the same degree of crystallinity under all conditions. Chrysotile particle ends showed signs of dissolution, and some tremolite-actinolite particles had rounded edges.
• The authors' conclusion: The authors concluded that removing iron from crocidolite through microbial iron respiration outperforms iron assimilation by other organisms, without altering the mineral structure. They also concluded that the crystal-chemical differences between chrysotile and tremolite-actinolite control how these minerals dissolve.
• Limitations the authors state:
  • The authors stated that more constraints are needed on release rates, starting asbestos amounts, reaction volumes and incubation times before biological and non-biological treatments can be compared properly.
  • The authors noted it is possible that the microbe-mineral interactions with crocidolite were limited to the fiber surface.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Actinolite, Chrysotile, Crocidolite, Tremolite.

Medical terms in this study, explained in our Lexicon: Crocidolite, Chrysotile, Tremolite, Actinolite, Asbestos, Amphibole Asbestos, Serpentine Group, Amphibole Group.

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