Investigation of the Bacterial Flagellar Motors through Magnetic Torque Wrench

Abstract

At low Reynolds number, bacteria such as Escherichia coli propel themselves by rotating a set of long flagella powered by nano-sized engines that are known as the bacterial flagellar motors. These bacterial flagellar motors, one of the largest and most complex biological rotary motors, consist of about 25 different proteins. They spin either clockwise or counterclockwise at speeds on the order of 100 Hz and exert torques on cells up to about 1000 pN to navigate toward favorable environments in response to chemical gradients. However, despite extensive studies in the structure and the regulation of the genes of the bacterial flagellar motors, we lack sufficient understanding of the underlying torque generating mechanisms that powers the motors, of how the motors suddenly shift rotational direction from clockwise to counterclockwise or vice versa, and how motor components such as rotor and stators function and interact. Here, we employ the magnetic torque wrench to investigate key aspects of the bacterial flagellar motor. The magnetic torque wrench can generate high rate throughput and broadly apply calibrated external torque to individual tethered bacterial cells. We will present preliminary experimental results on stalling torque, motor switching, and motor breaking of the bacterial flagellar motors.