| Budget Amount *help |
¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 2006: ¥1,400,000 (Direct Cost: ¥1,400,000)
Fiscal Year 2005: ¥2,100,000 (Direct Cost: ¥2,100,000)
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| Research Abstract |
Singly flagellated bacteria, Vibrio alginolyticus, move forward and backward by changing the rotational direction of their rotary motor. In free space, they move along almost the same tracks in a zigzag pattern. Near a rigid boundary, however, the track changes to a circular one only in backward motion and the backward speed is bigger than the forward speed.
In this study, the motion of a Vibrio cell swimming close to a rigid boundary has been calculated by use of the boundary element analysis. The swimming speed and the track depend on the pitch angle of the cell. The pitching motion is stable in forward motion and unstable in backward motion. A set of diagrammatic representation of the motion has been drawn. According to it, a cell swimming forward tends to keep a certain distance from the boundary since its pith motion is stable. The swimming speed of the cell is reduced by the boundary. A cell swimming backward moves either departing from the boundary or approaching the boundary since the pitch motion is unstable. In departing motion, the cell is less affected by the boundary so that the cell moves like it is in free space. In approaching motion, the interaction between the flagellum and the boundary becomes significant. As a consequence, the track changes circular one and the speed increases.
Bacterial cells with several flagella also move along circular tracks in forward motion. This is different from the motion of singly flagellated bacteria. The ratio of the size of the cell body and the size of the flagella is considered as an important factor introducing the difference.
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