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Novel methods of the bacterial motor characteristic measurement using AC field effects in a microfabricated electrode system are presented. Two methods are developed in this paper. One is the measurement of the external force-to-velocity characteristics (F-v) of swimming bacteria. Electrostatic orientation of bacteria parallel to the field lines is used to(More)
Bacteria such as Escherichia coli and Salmonella typhimurium swim by rotating their flagella, each of which consists of an external helical filament and a rotary motor embedded in the cell surface. The function of the flagellar motor has been examined mainly by tethering the flagellar filament to a glass slide and observing the resultant rotation of the(More)
A bacterial cell that has a single polar flagellum alternately repeats forward swimming, in which the flagellum pushes the cell body, and backward swimming, in which the flagellum pulls the cell body. We have reported that the backward swimming speeds of Vibrio alginolyticus are on average greater than the forward swimming speeds. In this study, we(More)
The Na(+)-driven flagellar motor in Vibrio alginolyticus rotates very fast. Rotation of a single flagellum on a stuck cell was measured by laser darkfield microscopy with submillisecond temporal resolution. The rotation rate increased with increasing external concentration of NaCl, and reached 1000 r.p.s. at 300 mM NaCl. The Na+ influx through the motor(More)
Swimming speeds and flagellar rotation rates of individual free-swimming Vibrio alginolyticus cells were measured simultaneously by laser dark-field microscopy at 25, 30, and 35 degrees C. A roughly linear relation between swimming speed and flagellar rotation rate was observed. The ratio of swimming speed to flagellar rotation rate was 0.113 microns, which(More)
The singly flagellated bacterium, Vibrio alginolyticus, moves forward and backward by alternating the rotational direction of its flagellum. The bacterium has been observed retracing a previous path almost exactly and swimming in a zigzag pattern. In the presence of a boundary, however, the motion changes significantly, to something closer to a circular(More)
Swimming speed (v) and flagellar-bundle rotation rate (f) of Salmonella typhimurium, which has peritrichous flagella, were simultaneously measured by laser dark-field microscopy (LDM). Clear periodic changes in the LDM signals from a rotating bundle indicated in-phase rotation of the flagella in the bundle. A roughly linear relation between v and f was(More)
The swimming pattern of bacteria with single polar flagella has usually been described as "run and reverse". We observed the swimming traces of monotrichously flagellated Vibrio alginolyticus cells and examined the relationship between the swimming pattern and the sense of progress. Swimming in regions other than a solid surface was confirmed to be linear(More)
The forward and backward swimming speeds and periods of a Vibrio alginolyticus strain that has a single polar flagellum were measured. The backward swimming speeds were 1.5 times greater than the forward ones on average and the average period of backward swimming was shorter than forward swimming. However, the swimming speed and period were not correlated.(More)