Bacterial Flagellar Motor: Proton-Powered Rotary Engine

Deep in the cell envelope of a swimming bacterium sits one of biology's few true rotary machines: the flagellar motor. This simulation renders the motor in 3D — a rotor ring surrounded by up to eleven MotA/MotB stator units, driven by the proton-motive force and spinning a helical filament — and lets you explore the real biophysics behind it. Change how many stators are engaged and how strong the proton-motive force is to see the motor's torque and speed shift along its measured torque-speed curve, drag the load slider between a light bead and the real flagellar bundle to see the operating point move between the flat, high-torque regime and the falling, high-speed regime, and trigger a CheY-P switching pulse to watch the rotor flip from smooth counter-clockwise running to the clockwise tumble that lets a bacterium re-aim itself.