TitleModeling torque versus speed, shot noise, and rotational diffusion of the bacterial flagellar motor.
Publication TypeJournal Article
Year of Publication2009
AuthorsMora, T, Yu, H, Wingreen, NS
JournalPhys Rev Lett
Date Published2009 Dec 11
KeywordsDiffusion, Escherichia coli, Escherichia coli Proteins, Flagella, Models, Biological, Molecular Motor Proteins, Rotation, Torque

We present a minimal physical model for the flagellar motor that enables bacteria to swim. Our model explains the experimentally measured torque-speed relationship of the proton-driven E. coli motor at various pH and temperature conditions. In particular, the dramatic drop of torque at high rotation speeds (the "knee") is shown to arise from saturation of the proton flux. Moreover, we show that shot noise in the proton current dominates the diffusion of motor rotation at low loads. This suggests a new way to probe the discreteness of the energy source, analogous to measurements of charge quantization in superconducting tunnel junctions.

Alternate JournalPhys. Rev. Lett.