A boundary element analysis of the wall effect on the bacterium swimming motion

Abstract

The speed of a bacterium that swims near a wall was numerically investigated by use of the boundary element method including the wall effect. The relationship between the swimming speed and the sizes of the cell body was mainly studied. A rotating flagellum of a bacterium propels its cell body and the propulsive force balances to the drag of the cell body. The cell body also rotates in the opposite direction to the flagellar rotation to cancel the torque produced by the flagellum. The force and torque are influenced by the presence of a wall and the swimming speed varies. The result shows that a bacterium with a cell body of the mean size observed in Vibrio alginolyticus swims slower when it moves near a wall than when it moves in free space even though a bacterium with a very small cell body swims faster near a wall.