Plasmid DNA is released from nanosized acicular material surface by low molecular weight oligonucleotides: exogenous plasmid acquisition mechanism for penetration intermediates based on the Yoshida effect

Our plain-English summary of Plasmid DNA is released from nanosized acicular material surface by low molecular weight oligonucleotides: exogenous plasmid acquisition mechanism for penetration intermediates based on the Yoshida effect, by N. Yoshida, K. Ide (Applied Microbiology and Biotechnology, 2008).

The study

• Authors: N. Yoshida, K. Ide
• Journal: Applied Microbiology and Biotechnology
• Published: 2008;80(5):813-21
• Cited by: 11 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

When a colloidal solution consisting of nanosized acicular material and bacterial cells is stimulated with sliding friction at the interface between the hydrogel and interface-forming material where the frictional coefficient increases rapidly, the nanosized acicular material accompanying the bacterial cells forms a penetration intermediate. This effect is known as the Yoshida effect in honor of its discoverer. Through the Yoshida effect, a novel property in which penetration intermediates incorporate exogenous plasmid DNA has been identified. This report proposes a possible mechanism for exogenous plasmid acquisition by penetration intermediates in the Yoshida effect. Escherichia coli cells, pUC18, and chrysotile were used as recipient cells, plasmid DNA, and nanosized acicular material, respectively. Even when repeatedly washing the mixture consisting of pUC18 and chrysotile, transformation efficiency by pUC18 was stable. Accordingly, pUC18 adsorbed onto chrysotile was introduced into recipient E. coli cells. At saturation, the amount of pUC18 adsorbed onto chrysotile was 0.8-1.2 microg/mg. To investigate whether pUC18 adsorbed on chrysotile is replicated by polymerase, polymerase chain reaction (PCR) was carried out with the chrysotile. Amplification of the beta-lactamase gene coded in pUC18, which was adsorbed onto chrysotile, was strongly inhibited. This suggests that DNA adsorbed onto chrysotile is not replicated in vivo. When we searched for substances to release pUC18 adsorbed onto chrysotile, we found that a 300-bp single- or double-stranded segment of DNA releases pUC18 from chrysotile. Competitive adsorption onto chrysotile between double-stranded DNA and pUC18 was then examined through the Yoshida effect. The 310- and 603-bp double-stranded nucleotides caused 50% competitive inhibition at the same molar ratio with pUC18. Hence, the adsorbed region of pUC18 is about 300 bp in length. As the culture period for recipient cells increases, transformation efficiency decreases while the expression levels of small RNA of 300-600 bp also decrease. These results suggest that pUC18 adsorbed onto chrysotile can be released by 300-bp small RNA, replicated by DNA polymerase, and transferred to daughter cells.

In plain English

This was a laboratory transformation study, not a health study. The authors used Escherichia coli JM109, pUC18 plasmid, and a chrysotile colloidal solution (fibres mostly 50–70 nm wide), spread on agar and rubbed with a polystyrene stir stick (hydrogel exposure, the "Yoshida effect"). Transformation efficiency stayed at 6.0x10^6 per µg even after the chrysotile–plasmid mixture was washed one to six times, indicating the plasmid taken up was chrysotile-bound. At saturation, 0.8–1.2 µg of pUC18 adsorbed per mg of chrysotile. In PCR, amplification of the beta-lactamase gene fell as chrysotile rose, with none at 4.41 mg/ml. A single-stranded 12-mer at 400 µg/ml did not reduce transformant numbers, whereas herring DNA averaging 300 bp at 400 µg/ml lowered counts to 90% of controls (single-stranded) and 65% (double-stranded); the authors inferred release of pUC18 by substitution. Fragments of 310 bp (7.0 ng) and 603 bp (13.0 ng) each halved transformation of 60 ng pUC18; 118 and 194 bp did not. Transformation efficiency fell as recipient cells were cultured 24 to 120 h; in separate cells harbouring pUC18, total RNA, predominantly 300–600 bp small RNA, also fell.

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) experimental microbiology study of plasmid transformation mediated by chrysotile fibres and sliding friction
• Who was studied: Escherichia coli JM109 cells as recipients, pUC18 plasmid DNA, and chrysotile colloidal solution; laboratory work at the University of Miyazaki, Japan (published 2008)
• Exposure: chrysotile fibres (nanosized acicular material) in colloidal solution, 95% with diameters 50–70 nm and lengths 0.34–2.30 µm, applied with sliding friction on agar hydrogel
• Main results:
  • Transformation efficiency of E. coli with pUC18 stayed at 6.0x10^6 per µg after the chrysotile–plasmid mixture was washed one to six times
  • At saturation 0.8–1.2 µg of pUC18 was adsorbed per mg of chrysotile
  • PCR amplification of the beta-lactamase gene of pUC18 was abolished at a chrysotile concentration of 4.41 mg/ml in the reaction mixture
  • Single-stranded 12-mer DNA at 400 µg/ml did not inhibit transformation
  • Single-stranded herring DNA (average length 300 bp) at 400 µg/ml reduced the number of transformants to 90% of controls
  • Double-stranded herring DNA (average length 300 bp) at 400 µg/ml reduced the number of transformants to 65% of controls
  • In competition experiments with 60 ng pUC18, 118 and 194 bp linear DNA did not inhibit transformation; 7.0 ng of 310-bp and 13.0 ng of 603-bp DNA each produced 50% inhibition, giving an estimated adsorption site of about 310 bp
  • In E. coli JM109 already harbouring pUC18 and grown on ampicillin plates for 1 to 5 days, total RNA band intensity fell from a mean of 138 at 24 h to 84.7 at 120 h
  • Separately, transformation efficiency was highest with recipient cells cultured for 24 h and decreased with longer culture
• The authors' conclusion: The authors concluded that plasmid DNA adsorbed onto chrysotile is carried into recipient cells but is not replicated while adsorbed, and that release by roughly 300-bp small RNA is needed before replication and transfer to daughter cells; they presented this as a proposed mechanism supporting their hypothesis
• Limitations the authors state:
  • The authors stated that the mechanism and the affinity of plasmid DNA binding to chrysotile were not known
  • The release mechanism by small RNA was presented as a hypothesis rather than a demonstrated process
  • Some competition results were reported without presenting 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: Acicular, Chrysotile.

Related studies

• Discovery and application of the Yoshida effect: nano-sized acicular materials enable penetration of bacterial cells by sliding friction force — N. Yoshida (2007)
• Chrysotile asbestos fibers mediate transformation of Escherichia coli by exogenous plasmid DNA — N. Yoshida, T. Ikeda, et al. (2001)
• Escherichia coli cells penetrated by chrysotile fibers are transformed to antibiotic resistance by incorporation of exogenous plasmid DNA — N. Yoshida, K. Kodama, et al. (2002)
• Chestnut bur-shaped aggregates of chrysotile particles enable inoculation of Escherichia coli cells with plasmid DNA — N. Yoshida, Y. Saeki (2004)
• Asbestos fibers mediate transformation of monkey cells by exogenous plasmid DNA — J.D. Appel, T.M. Fasy, et al. (1988)
• Quantitative detection of asbestos fiber in gravelly sand using elastic body-exposure method — N. Yoshida, K. Takebe (2006)

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