Toxicity and mutagenesis of chrysotile asbestos to Agrobacterium radiobacter

Our plain-English summary of Toxicity and mutagenesis of chrysotile asbestos to Agrobacterium radiobacter, by N. Yoshida, T. Naka, T. Sengoku, et al (Current Microbiology, 2001).

The study

• Authors: N. Yoshida, T. Naka, T. Sengoku, K. Ogawa
• Journal: Current Microbiology
• Published: 2001;42(6):398-402
• Cited by: 3 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The mutation of Agrobacterium radiobacter cells exposed to chrysotile asbestos was examined by the random amplified polymorphic DNA (RAPD) method. Approximately 1.4 kbp of DNA in A. radiobacter, which was not amplified strongly in the cells that were not exposed to asbestos, was amplified in the cells that were exposed to asbestos. Mutation in genomic DNA of A. radiobacter was found to be induced by asbestos. Specific DNA that was amplified by asbestos present in PCR products and that which exists latently in genomic DNA were cloned, and these sequences were then determined and compared. It was shown that one of the mutations by the asbestos in the A. radiobacter occurred only in the primer annealed region and was a point mutation or deletion.

In plain English

This was a laboratory experiment on a soil bacterium, Agrobacterium radiobacter (strain IFO12665b1). It was not a study of people or animals. The authors grew the bacteria for 24 hours in liquid medium containing chrysotile asbestos at concentrations printed as 2–20 mg/ml. Growth fell as the amount of asbestos rose. At 20 mg/ml, growth was 22% of the unexposed control after 12 hours. At 2–10 mg/ml it was 88–98% of the control after 24 hours (data not shown). Using a DNA fingerprinting method called RAPD, the authors found a strongly amplified piece of DNA, about 1.4 kbp long, in asbestos-exposed bacteria that was not detected in unexposed bacteria. A 1.0-kbp band seen in the controls disappeared. When they compared this piece with the corresponding stretch cloned from the bacterial genome, the sequences matched except where the test primer attaches. They interpreted this as a point mutation or deletion. The authors concluded that their data imply chrysotile is directly genotoxic to bacterial cells. They stated that the mutation frequency was obscure.

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 on bacterial cultures, using the RAPD DNA method, DNA cloning and sequencing
• Who was studied: Cultures of the bacterium Agrobacterium radiobacter strain IFO12665b1, obtained from the Institution for Fermentation, Osaka, Japan; four independent determinations of exposed cells are shown in the gel figure
• Exposure: Chrysotile asbestos (from Kishida Chemical Co. Ltd., Osaka), washed and autoclaved, added to culture medium at concentrations printed as 2–20 mg/ml; bacteria cultured at 30°C for 24 h; DNA analysis used cells grown with or without 20 mg/ml
• Main results:
  • In bacteria grown with 20 mg/ml asbestos, growth was strongly inhibited: 22% of the control after 12 h
  • In bacteria grown with 2–10 mg/ml asbestos, growth was not strongly inhibited: 88–98% of the control after 24 h (data not shown)
  • A 1.4-kbp DNA product (called ASDA) was very intense in asbestos-exposed bacteria and not detected in unexposed control bacteria
  • A 1.0-kbp DNA band present in control bacteria disappeared in asbestos-exposed bacteria
  • 51 bp of the cloned ASDA showed 76% identity with part of the human centromere protein B gene
  • The ASDA sequence was present as a single copy in the bacterial genome
  • The ASDA from exposed cells and the corresponding sequence cloned from the genome matched except in the primer-annealed regions; the authors proposed a three-point mutation or a deletion there
• The authors' conclusion: The authors concluded that their data imply chrysotile asbestos is directly genotoxic to target bacterial cells, with a point mutation or deletion expected in genomic DNA
• Limitations the authors state:
  • The authors stated that the mutation frequency was obscure
  • The authors stated that the relationship between the centromere-protein-like sequence and asbestos-induced mutation was unclear
  • The authors stated that the molecular mechanisms of asbestos-induced mutagenesis remain unclear

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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