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Bacterial flagellum Created 2026-10-24 Updated 2026-11-05
A bacterial flagellum is a rotary swimming appendage comprising a filament, a flexible hook and an envelope-associated bacterial flagellar motor. Rotation of the helical filament converts motor torque into propulsion through a liquid. It differs structurally from a eukaryotic cilium, which bends through the action of dynein on microtubules. In the classic tethered-cell experiment, attachment through a flagellar filament lets the cell body rotate instead, making otherwise hard-to-see motor rotation visible by microscopy. [ref]
Flagellar rotation and the mechanism of bacterial motility by M. Silverman and M. Simon. Silverman and Simon, 1974, Flagellar rotation and the mechanism of bacterial motility
M. Silverman 2026-11-05
M. Silverman coauthored the 1974 demonstration that bacterial flagella drive motility by rotation. Antibody-mediated attachment of a flagellum to a surface made the bacterial body rotate instead, turning an otherwise difficult-to-observe motor movement into a visible cellular motion.[ref]
Flagellar rotation and the mechanism of bacterial motility by M. Silverman and M. Simon. 1974 original report, pp. 73–74
[ref]Change in direction of flagellar rotation is the basis of the chemotactic response in Escherichia coli by S. H. Larsen and others. Opening account of the tethered-cell demonstration
The experiment illustrates a mechanical strategy: constrain one member of a moving assembly and observe the resulting motion of the other. It supplied evidence for a rotary motor rather than requiring flagellar propulsion to be inferred only from the swimming trajectory.