Figure 3. Models showing correlation between structural elaboration of the flagellar motor and its stator type.

Flagellar motors with single H⁺-driven stator systems (e.g. Salmonella) have P- and L-rings alone. Motors with dual H⁺-driven stator systems have an extra ring surrounding the P-ring formed by the MotY protein alone. Motors with Na⁺-driven motors have two periplasmic rings, the T-ring (MotX and MotY) and H-ring (FlgO, FlgP and FlgT), decorating the P- and L-rings, respectively. Note that the boundaries between the P- and L-rings and their decorations are tentative in these schematics.