Bacterial flagellar motor

Q Rev Biophys. 2008 May;41(2):103-32. doi: 10.1017/S0033583508004691.


The bacterial flagellar motor is a reversible rotary nano-machine, about 45 nm in diameter, embedded in the bacterial cell envelope. It is powered by the flux of H+ or Na+ ions across the cytoplasmic membrane driven by an electrochemical gradient, the proton-motive force or the sodium-motive force. Each motor rotates a helical filament at several hundreds of revolutions per second (hertz). In many species, the motor switches direction stochastically, with the switching rates controlled by a network of sensory and signalling proteins. The bacterial flagellar motor was confirmed as a rotary motor in the early 1970s, the first direct observation of the function of a single molecular motor. However, because of the large size and complexity of the motor, much remains to be discovered, in particular, the structural details of the torque-generating mechanism. This review outlines what has been learned about the structure and function of the motor using a combination of genetics, single-molecule and biophysical techniques, with a focus on recent results and single-molecule techniques.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Bacteria / metabolism*
  • Bacterial Physiological Phenomena*
  • Bacterial Proteins / physiology*
  • Biophysics / methods*
  • Flagella / physiology*
  • Models, Biological
  • Models, Molecular
  • Molecular Conformation
  • Molecular Motor Proteins / physiology*
  • Signal Transduction
  • Torque


  • Bacterial Proteins
  • Molecular Motor Proteins