Bacterial flagella: Do they rotate or do they propagate waves of bending?

Conclusion

Whether the flagellum is rigid or nearly so or whether there are moving helical lines of contraction (Astbury et al. 1955,Lowy andSpencer 1968), “incompatible sets of bonds at different radii” (Klug 1967), subunits which alter their configurational states (Asakura 1966, 1970) or slip between subunits carried by edge dislocations (Harris andScriven 1971, 1973), the prevention of apparent rotation of the flagellum will result in actual rotation of the body. The differences between the two classes of mechanisms have a scale beyond the power of resolution of the light microscope. Because of this it is most unlikely that direct observation of a moving bacterium will provide evidence favouring any one of the mechanisms. The mechanism of movement of bacterial flagella remains unknown.