Chrysotile asbestos fibers mediate transformation of Escherichia coli by exogenous plasmid DNA

Our plain-English summary of Chrysotile asbestos fibers mediate transformation of Escherichia coli by exogenous plasmid DNA, by N. Yoshida, T. Ikeda, T. Yoshida, et al (FEMS Microbiology Letters, 2001).

The study

• Authors: N. Yoshida, T. Ikeda, T. Yoshida, T. Sengoku, K. Ogawa
• Journal: FEMS Microbiology Letters
• Published: 2001;195(2):133-7
• Cited by: 25 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The ability of chrysotile asbestos fibers to introduce the exogenous plasmid pUC18 into Escherichia coli JM109 cells was tested. Cells were transformed with pUC18 DNA although the frequency of transformation was quite low: 759+/-301 transformants were obtained per microgram of pUC18. Plasmids were purified from E. coli which had been transformed by mediation with chrysotile asbestos. Following this, the plasmids were confirmed to be pUC18 by Southern hybridization. This asbestos-mediated transformation was optimal within 5 min when 10 mg ml(-1) of asbestos was used. Plasmids up to 7.69 kb were introduced by this method.

In plain English

This was a laboratory experiment in bacteria. The authors tested whether chrysotile asbestos fibers could carry the plasmid pUC18 into Escherichia coli JM109 cells, scoring transformation as ampicillin-resistant colonies. Mixing about 5x10(8) cells with 1 microgram of pUC18 and 20 mg of chrysotile for 30 min at 37 degrees C produced about 759 plus or minus 301 transformants per microgram of pUC18, which the authors described as a quite low efficiency. No transformants arose from cells plus pUC18 alone, from cells plus chrysotile alone, or from cells resuspended in a calcium solution with pUC18, and the structurally similar clay minerals kaolinite and bentonite produced no transformation. Plasmids recovered from five randomly picked resistant colonies matched pUC18 on agarose gel electrophoresis and Southern hybridization. Transformation was optimal within 5 min (about 1700 transformants) and at 10 mg per ml of chrysotile. Plasmids up to 7.69 kb (pUC18A4) were introduced, with 40% fewer transformants than with 2.69 kb pUC18. DNase treatment abolished transformation.

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: in vitro bacterial laboratory experiment testing asbestos-mediated plasmid transformation
• Who was studied: Escherichia coli JM109 cells in culture (about 5x10(8) cells per 1000 microlitres of stationary-phase culture), laboratory study in Japan; four independent experiments for the main transformation assay
• Exposure: chrysotile asbestos fibers (20 mg, or 5 to 40 mg per ml) mixed with plasmid DNA; kaolinite and bentonite used as comparison minerals
• Main results:
  • Chrysotile asbestos yielded about 759 plus or minus 301 transformants per microgram of pUC18, which the authors called a quite low efficiency
  • No transformants were obtained with asbestos but without plasmid, nor from cells plus pUC18 without mineral; kaolinite and bentonite gave no transformation
  • No transformants were obtained when cells were treated with the calcium solution plus pUC18 instead of asbestos
  • Plasmids from five randomly picked ampicillin-resistant colonies ran at the same size as pUC18 (2.69 kb) and were confirmed by Southern hybridization with a pUC18 probe
  • Transformant numbers rose with plasmid amount: adding 10 and 5 micrograms of pUC18 with 20 mg per ml asbestos gave about 8000 and about 2300 transformants
  • Reaction time optimum was 5 min with about 1700 transformants
  • Varying asbestos from 40 to 5 mg per ml raised transformants from about 1100 to about 3300; the authors identified 10 mg per ml as optimal
  • Transformation efficiency was unaffected between 2.69 and 4.49 kb (860, 840 and 830 transformants for pUC18MTL42, pUC18MTL75 and pUC18-180), while the 7.69 kb pUC18A4 gave 40% fewer transformants than pUC18
  • Treating the reaction mixture with 0.5 to 2.0 U of DNase gave no transformants, leading the authors to suggest uptake of free rather than asbestos-bound plasmid
• The authors' conclusion: The authors concluded that chrysotile asbestos promotes the intracellular uptake of plasmids into bacterial cells, by a mechanism differing from the calcium/heat-pulse method, and stated that their data reveal asbestos fibers have the potential to cause bacterial mutations.
• Limitations the authors state:
  • The authors reported electron microscope observations of asbestos binding to E. coli cells without showing the data

Topics

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

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

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• Mutagenesis of Escherichia coli (CSH50) by asbestos — M.G. Cleveland (1984)

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