Figure 1.

Schematic models of the external flagellum of E. coli (A and C) and periplasmic flagella of B. burgdorferi (B and D). Periplasmic flagella are distinct from the external flagella, as they are enclosed within the outer membrane and their flagellar motors are considerably larger and more complex. However, the core architecture of the two flagellar types is comparable. Shared structures include the MS ring, the C ring, the rod, the hook, the filament, the stator, and the export apparatus.