The unidirectional flagellar motor of Rhodobacter sphaeroides WS8 can rotate either clockwise or counterclockwise: characterization of the flagellum under both conditions by antibody decoration.

A variant of Rhodobacter sphaeroides WS8 has been isolated which when tethered has a cell body that rotates counterclockwise instead of clockwise. Antibody decoration in vivo has shown that the filament on the variant has handedness opposite to that of the normal form. In both cases the cell body is pushed by the rotating flagellum.