Figure 2.

Intact flagellar motor structures reveal dramatic differences among species. Depicted for each species, from top to bottom, are the deposited class average of the motor, a cartoon model drawn from the class average, and a 3D reconstruction of the map. E. coli possess the simplest motor, resulting in a functional flagellum (EMDB 5311). Vibrio spp. have evolved additional rings that increase rotational speed. H. pylori (EMDB 8459), representing ε-proteobacteria, and B. burgdorferi (EMDB 0534), representing spirochetes, separately evolved structures that stabilize stators and increase rotor diameter, leading to greater torque generation.