Fig. 15: Structure of a Bacterial Flagellum

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.

Illustration of the Structure of a bacterial Flagellum.jpg by Gary E. Kaiser, Ph.D.
Professor of Microbiology, The Community College of Baltimore County, Catonsville Campus
This work is licensed under a Creative Commons Attribution 4.0 International License.
Based on a work at

Creative Commons License

Last updated: July, 2018
Please send comments and inquiries to Dr. Gary Kaiser