The filament of the bacterial flagellum is connected to a hook which, in turn, is attached to a rod. The basal body of the flagellum consists
of a rod and a series of rings that anchor the flagellum to the cell wall
and the cytoplasmic membrane. In gram-negative bacteria, the L ring anchors the flagellum to the lipopolysaccharide layer of the outer membrane while the P ring anchors the flagellum to the peptidoglycan portion of the cell wall. The MS rings are located in the cytoplasmic membrane and the C ring (the rotor) in the cytoplasm. The stator, composed of MotA and MotB proteins surround the MS and C rings of the motor and function to generate torque for rotation of the flagellum. Energy for rotation comes from the proton motive force provided by protons moving through the Mot proteins.