Abstract
Residence times of singly flagellated bacteria, Vibrio alginolyticus, swimming in various conditions were measured and their frequency distributions were compared each other in order to examine their dependencies on swimming directions and the distance from a boundary. A mutant being able to swim only forward, YM42, and another mutant that could swim only backward, NMB102, were used. Each of the suspensions of them was sealed in a chamber, which was about 150μm in depth. Because the practical focal depth of the microscope was limited to 10μm, we could measure the residence time for a bacterium stayed only within the layer. In forward motion, the distributions are similar irrespective of the distance from a boundary. In backward motion, especially near the boundary, the residence time of a bacterium swimming straight tends to be shorter than that of a bacterium swimming along a curve. These results are consistent with a deduction from diagrammatic representations based on the numerical simulation which had been carried out to explain the wall effect on the bacterial motion close to a boundary.
