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Pilus retraction powers bacterial twitching motility

Naturevolume 407pages98102 (2000) | Download Citation



Twitching and social gliding motility allow many Gram negative bacteria to crawl along surfaces, and are implicated in a wide range of biological functions1. Type IV pili (Tfp) are required for twitching and social gliding, but the mechanism by which these filaments promote motility has remained enigmatic1,2,3,4. Here we use laser tweezers5 to show that Tfp forcefully retract. Neisseria gonorrhoeae cells that produce Tfp actively crawl on a glass surface and form adherent microcolonies. When laser tweezers are used to place and hold cells near a microcolony, retractile forces pull the cells toward the microcolony. In quantitative experiments, the Tfp of immobilized bacteria bind to latex beads and retract, pulling beads from the tweezers at forces that can exceed 80 pN. Episodes of retraction terminate with release or breakage of the Tfp tether. Both motility and retraction mediated by Tfp occur at about 1 µm s-1 and require protein synthesis and function of the PilT protein. Our experiments establish that Tfp filaments retract, generate substantial force and directly mediate cell movement.

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We thank our colleagues in the Sheetz and So labs for invaluable technical assistance and stimulating discussions; E. Barklis and L. Kenney for critical comments on the manuscript; and M. Koomey for providing bacterial strains. This work was supported by NIH grants to M.S. and M.P.S. A.J.M. received pre-doctoral support from an NIH NRSA grant and postdoctoral support from the Cancer Research Fund of the Damon Runyan-Walter Winchell Foundation.

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    • Alexey J. Merz

    Present address: Department of Biochemistry, Dartmouth Medical School, Hanover, New Hampshire, 03755-3844, USA

    • Michael P. Sheetz

    Present address: Department of Biological Sciences, Columbia University, New York, New York, 10027, USA


  1. Department of Molecular Microbiology and Immunology, Oregon Health Sciences University, Portland, 97201-3098, Oregon, USA

    • Alexey J. Merz
    •  & Magdalene So
  2. Department of Cell Biology, Duke University Medical School, Durham, 27705, North Carolina, USA

    • Michael P. Sheetz


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Correspondence to Michael P. Sheetz.

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