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Related Concept Videos

Bacterial Transformation01:33

Bacterial Transformation

In 1928, bacteriologist Frederick Griffith worked on a vaccine for pneumonia, which is caused by Streptococcus pneumoniae bacteria. Griffith studied two pneumonia strains in mice: one pathogenic and one non-pathogenic. Only the pathogenic strain killed host mice.Griffith made an unexpected discovery when he killed the pathogenic strain and mixed its remains with the live, non-pathogenic strain. Not only did the mixture kill host mice, but it also contained living pathogenic bacteria that...
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Transposons make up a significant part of genomes of various organisms. Therefore, it is believed that transposition played a major evolutionary role in speciation by changing genome sizes and modifying gene expression patterns. For example, in bacteria, transposition can lead to conferring antibiotic resistance. Movement of transposable elements within the genetic pool of pathogenic bacteria can aid in transfer of antibiotic-resistant genetic elements. In eukaryotes, transposons can carry out...
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Transformation01:26

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Microbial communities are dynamic environments where cell lysis releases free DNA into the surroundings. Other cells can take up this extracellular DNA through a process known as transformation.When a cell incorporates this foreign DNA into its genome, resulting in genetic modification, the process is known as transformation. Cells capable of this process are termed competent. Competence can be natural, as observed in certain bacteria and archaea, or artificially induced in the...

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Updated: Jun 9, 2026

Examining the Conformational Dynamics of Membrane Proteins in situ with Site-directed Fluorescence Labeling
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Published on: May 29, 2011

Structural basis for DNA processing and membrane translocation by ComEC in natural transformation.

Hisato Hirano1, Naoko Tsuji2, Shinobu Chiba2

  • 1Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo, Japan.

Science (New York, N.Y.)
|April 16, 2026
PubMed
Summary
This summary is machine-generated.

Bacterial natural transformation uses ComEC protein to import extracellular DNA. New cryo-EM structures show ComEC processes double-stranded DNA by cleaving one strand and guiding the other into the cell for horizontal gene transfer.

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Area of Science:

  • Microbiology
  • Molecular Biology
  • Structural Biology

Background:

  • Natural transformation is a key mechanism for bacterial horizontal gene transfer.
  • The ComEC protein facilitates DNA uptake but its structure and function were unclear.

Purpose of the Study:

  • To elucidate the structure and function of the ComEC protein.
  • To provide a structural basis for ComEC's role in natural transformation.

Main Methods:

  • Cryo-electron microscopy (cryo-EM) to determine structures of ComEC.
  • Biochemical analyses to study ComEC activity.

Main Results:

  • Determined cryo-EM structures of ComEC in DNA-free, single-stranded DNA (ssDNA), and double-stranded DNA (dsDNA)-bound states.
  • Revealed ComEC cleaves one dsDNA strand extracellularly and translocates the other through a membrane pore.
  • Identified a positively charged pore within the membrane domain crucial for DNA translocation.

Conclusions:

  • ComEC acts as a DNA processing and translocation machine during natural transformation.
  • Structural insights explain ComEC's dual role in DNA cleavage and inner membrane transport.
  • Findings provide a mechanistic understanding of horizontal gene transfer in bacteria.