Fig. 1.

Schematic showing the basic parts of the BFM. A bacterium has, on average, four flagellae, each attached to the basal body of a motor via a flexible hook. The M, S, and C rings of the basal body are together called the rotor. FliG proteins (26 copies of which are assumed here) are placed around the periphery of the C ring. These interact with the MotA loops of the stator to generate torque and rotate the flagella. Stators are composed of MotA and MotB subunits, the latter of which attaches the stators to the peptidoglycan layer, allowing for torque generation via the MotA–FliG interaction. A motor can have between 1 and 11 engaged stators, depending on the load (2, 31, 32).