Measuring the Torque Produced by the Flagellar Motor in Pseudomonas aeruginosa*

Many motile bacteria, including Pseudomonas aeruginosa, achieve motility by using their flagellar motor to generate a torque that rotates a helical filament and propels their body forward. When swimming near a surface, P. aeruginosa follows relatively curved trajectories, spontaneously retreating by switching the direction of the flagellar motor’s rotation. The aim of this work is to experimentally measure the motion of P. aeruginosa near a surface to compute the torque required to rotate the flagellum. With its simple body structure, P. aeruginosa is a prime model organism for performing numerical simulations of bacterial motility near a surface. We have developed an algorithm to track and reconstruct the three-dimensional shape of motile bacteria imaged with total internal reflection fluorescence (TIRF) microscopy. The reconstructed bacterial trajectories are input into a computational fluid dynamics model to determine the torque acting on the bacterial bodies. We report preliminary measurements of the torque produced by the flagellar motor in P. aeruginosa.