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Published Online December 18, 2008
Science DOI: 10.1126/science.1164346

Reports

Submitted on August 7, 2008
Accepted on November 24, 2008

Electron Cryomicroscopy of E. coli Reveals Filament Bundles Involved in Plasmid DNA Segregation

Jeanne Salje 1*, Benoit Zuber 2, Jan Löwe 2

1 MRC Laboratory of Molecular Biology, Hills Road, Cambridge, CB2 0QH, UK.; Present address: Kyoto University, Department of Biophysics, Faculty of Science, Oiwake Kitashirakawa, Sakyo-Ku, Kyoto 606-8502, Japan.
2 MRC Laboratory of Molecular Biology, Hills Road, Cambridge, CB2 0QH, UK.

* To whom correspondence should be addressed.
Jeanne Salje , E-mail: jsalje{at}mrc-lmb.cam.ac.uk

Bipolar elongation of filaments of the bacterial actin homologue ParM drives movement of newly replicated plasmid DNA to opposite poles of a bacterial cell. We used a combination of vitreous sectioning and electron cryotomography to study this DNA partitioning system directly in native, frozen cells. The diffraction patterns from overexpressed ParM bundles in electron cryotomographic reconstructions were used to unambiguously identify ParM filaments in E. coli cells. Using a low-copy number plasmid encoding components required for partitioning, we observed small bundles of 3 to 5 intracellular ParM filaments that were situated close to the edge of the nucleoid. We propose that this may indicate capture of plasmid DNA within the periphery of this loosely defined, chromosome-containing region.


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
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Science. ISSN 0036-8075 (print), 1095-9203 (online)