Studying Bacterial Swimming, One Cell at a Time

University Of Pittsburgh, Pittsburgh PA

Investigators

Abstract

This project focuses on measurements of swimming bacteria in optical traps in order to study the fundamental properties of bacterial propulsion. A particular goal of the project is to determine the relationship between the structures of bacterial flagellum (or its bundles) and the propulsion matrix, which relates the translational and the rotational velocities of the flagellum to the torque and the force propelling the bacterium. Once the propulsion matrix is known, dynamical properties such as forces, torques, swimming speed, power, and swimming efficiency can be obtained from measurements of the angular velocity of the motor. Preliminary measurements have shown promising results, and the proposed research herein attempts to lead the experiment to the next step by comparing the measured propulsion matrix elements with calculations using helix coils as a model flagellum. The project will also address the issue of flagellar bundling and unbundling transitions by trapping two bacteria in close proximity to each other. Given the size of the bacterial cell body and the flagellum, it is expected that thermal noise will have an effect on the performance of the propulsion apparatus. The noise will be studied by examining fluctuations in the torque and thrust, and the resulting bacterial trajectories. A significant part of this research is to educate and train students in an area that is very attractive to students because the underlying biological/physical phenomena are intriguing and the mathematical theory is challenging and beautiful.