Long helical filaments are not seen encircling cells in electron cryotomograms of rod-shaped bacteria

Biochem Biophys Res Commun. 2011 Apr 22;407(4):650-5. doi: 10.1016/j.bbrc.2011.03.062. Epub 2011 Mar 16.

Abstract

How rod-shaped bacteria form and maintain their shape is an important question in bacterial cell biology. Results from fluorescent light microscopy have led many to believe that the actin homolog MreB and a number of other proteins form long helical filaments along the inner membrane of the cell. Here we show using electron cryotomography of six different rod-shaped bacterial species, at macromolecular resolution, that no long (> 80 nm) helical filaments exist near or along either surface of the inner membrane. We also use correlated cryo-fluorescent light microscopy (cryo-fLM) and electron cryo-tomography (ECT) to identify cytoplasmic bundles of MreB, showing that MreB filaments are detectable by ECT. In light of these results, the structure and function of MreB must be reconsidered: instead of acting as a large, rigid scaffold that localizes cell-wall synthetic machinery, moving MreB complexes may apply tension to growing peptidoglycan strands to ensure their orderly, linear insertion.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacillus subtilis / metabolism
  • Bacillus subtilis / ultrastructure
  • Bacteria / metabolism*
  • Bacteria / ultrastructure*
  • Borrelia burgdorferi / metabolism
  • Borrelia burgdorferi / ultrastructure
  • Caulobacter crescentus / metabolism
  • Caulobacter crescentus / ultrastructure
  • Cryoelectron Microscopy
  • Cytoskeleton / ultrastructure*
  • Escherichia coli / metabolism
  • Escherichia coli / ultrastructure
  • Escherichia coli Proteins / analysis
  • Escherichia coli Proteins / metabolism*
  • Vibrio cholerae / metabolism
  • Vibrio cholerae / ultrastructure

Substances

  • Escherichia coli Proteins
  • MreB protein, E coli