Soil fungal hyphae bind and attack asbestos fibers

Our plain-English summary of Soil fungal hyphae bind and attack asbestos fibers, by E. Martino, L. Prandi, I. Fenoglio, et al (Angewandte Chemie, 2003).

The study

• Authors: E. Martino, L. Prandi, I. Fenoglio, P. Bonfante, S. Perotto, B. Fubini
• Journal: Angewandte Chemie
• Published: 2003;42(2):219-22
• Cited by: 28 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Summary of the article

Asbestos fibers spread over wide areas of soil cannot be removed and need to be inactivated in place. Iron is known to contribute to asbestos toxicity. Researchers at the University of Torino, Italy, therefore asked whether soil fungi could bind crocidolite (blue asbestos) fibers, extract iron from them and reduce their ability to generate free radicals. Fungi were chosen for their ability to grow on silicates, produce siderophores (iron chelators) and tolerate metals. They were grown in liquid culture with crocidolite (9.2 mg/mL in Czapek glucose medium). None of the fungi tested was inhibited in biomass production. Crocidolite increased growth by more than 65% in Geomyces pannorum and in three strains of Oidiodendron maius. All fungi removed fibers from suspension and bound them to their hyphae. After 42 days, most species released substantial amounts of iron from the fibers. Fusarium oxysporum, Mortierella hyalina and O. maius E were the most active per gram of biomass. Fibers alone released no detectable iron. Iron extraction paralleled siderophore secretion and was not exhausted after 45 days. The iron mobilized corresponded to six to seven iron atoms per nm2, which the authors estimated as two or more layers below the fiber surface. In EPR tests, fibers incubated for 45 days with F. oxysporum were fully inactivated in their potential to generate hydroxyl radicals. Contact with fibers changed the fungal extracellular protein profiles, including induction of a manganese superoxide dismutase in G. pannorum. The authors concluded that fungi may be possible agents for decontaminating asbestos-polluted soils.

PubMed has no abstract for this study, and the article doesn't print one. We wrote this summary from the full article with the help of AI. It is not the authors' wording.

In plain English

This was a laboratory study of asbestos fibers and soil fungi. It did not involve people or animals. The authors grew several soil fungi in liquid culture with crocidolite (blue asbestos) fibers. They wanted to know whether the fungi could bind the fibers and pull iron out of them, because iron is known to contribute to asbestos toxicity. None of the fungi grew less with crocidolite present, and four grew more than 65% more. The fungi bound the fibers to their hyphae (fungal threads) and cleared them from the liquid. After 42 days, most species had removed substantial amounts of iron from the fibers and a few removed none. Without fungi, the fibers released no detectable iron. Every fungus that removed iron also secreted iron-binding substances called siderophores. Fibers kept for 45 days with the fungus Fusarium oxysporum no longer produced hydroxyl free radicals in a chemical test. The authors expected, but did not test here, that the fibers' biological activity might also be reduced. They concluded that fungi may be possible agents for decontaminating asbestos-polluted soils.

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: fungal cultures grown with asbestos fibers, plus cell-free chemical tests
• Who was studied: Soil fungi, not people. The species and strains named include Geomyces pannorum, G. vinaceous, Oidiodendron maius strains Zn, A, Cd and E, O. griseum, Mortierella hyalina, Fusarium oxysporum and sterile mycelium MUT840. They were chosen for their ability to grow on silicates, produce siderophores and tolerate metals.
• Exposure: Crocidolite (fibrous riebeckite, blue asbestos) fibers in liquid fungal culture, either in direct contact with the fungi or separated from them by a dialysis membrane. A cell-free test also exposed the fibers to the iron chelator desferrioxamine.
• Main results:
  • None of the fungi tested grew less (in biomass production) in the presence of crocidolite.
  • Crocidolite caused a significant growth increase of more than 65% in Geomyces pannorum and in three strains of Oidiodendron maius (Zn, Cd and A).
  • In liquid cultures, crocidolite fibers and fibrils were removed from the suspension and tightly bound to the fungal hyphae. This happened with all the fungi tested.
  • After growth with crocidolite, G. vinaceous and O. maius strains Zn, A and Cd removed no iron from the asbestos. G. pannorum, Mortierella hyalina, sterile mycelium MUT840, O. griseum and F. oxysporum removed substantial amounts of iron.
  • Measured as moles of iron released per gram of fungal biomass, Fusarium oxysporum, M. hyalina and O. maius E were the most active.
  • Without fungi, the crocidolite fibers released no detectable iron into the medium.
  • All fungi that caused iron release from the fibers also secreted siderophores (iron-binding substances).
  • The iron removed by the fungi corresponded to six to seven iron atoms per square nanometre. The authors estimated this as two or more layers below the fiber surface.
  • With F. oxysporum and M. hyalina, iron release was still continuing after 45 days of culture.
  • Fibers incubated for 45 days with F. oxysporum, then washed and dried, no longer generated hydroxyl radicals in a chemical (EPR) test. The untreated fibers did generate them.
  • The authors expected, without testing it in this article, that the fibers' biological activity might also be reduced after contact with the fungi.
  • Contact with the fibers changed the proteins the fungi released. An antioxidant enzyme, manganese superoxide dismutase (Mn-SOD), was among the proteins induced in G. pannorum.
• The authors' conclusion: The authors concluded that fungi may be possible agents for decontaminating asbestos-polluted soils, by binding fibers and by modifying the fiber surface through siderophores.

Topics

Medical terms in this study, explained in our Lexicon: Crocidolite, Silicate, Hydroxyl Radical, Superoxide.

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