Alignment and motion of uniflagellated bacteria in an electric field*

Most species of bacteria carry negative net charge. When motile bacteria are subject to an electric field, three physical factors are responsible for their motion: electrophoresis, electroosmosis, and swimming. Using Pseudomonas Aeruginosa, a uniflagellated bacterium as a model system, we record the speeds and trajectories of motile cells filled in a rectangular capillary whose ends are connected to a power supply. It has been observed that cells can be aligned by the electric field depending on its intensity. The alignment by the electric field makes it more convenient to study changes in rotation direction of the flagellar motor, as well as changes in the direction of travel for the cell body. Overall we aim to get a better comprehension of bacterial motion by aligning their trajectories using an external field.