Biophysical Journal 69: 250-263 (1995)
© 1995 the Biophysical Society

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Kara-Ivanov, M Articles by Caplan, S R Search for Related Content PubMed PubMed Citation Articles by Kara-Ivanov, M Articles by Caplan, S R

Fluctuations in rotation rate of the flagellar motor of Escherichia coli.

Department of Membrane Research and Biophysics, Weizmann Institute of Science, Rehovot, Israel.

ABSTRACT

The purpose of this work was to study the changes in rotation rate of the bacterial motor and to try to discriminate between various sources of these changes with the aim of understanding the mechanism of force generation better. To this end Escherichia coli cells were tethered and videotaped with brief stroboscopic light flashes. The records were scanned by means of a computerized motion analysis system, yielding cell size, radius of rotation, and accumulated angle of rotation as functions of time for each cell selected. In conformity with previous studies, fluctuations in the rotation rate of the flagellar motor were invariably found. Employing an exclusively counterclockwise rotating mutant ("gutted" RP1091 strain) and using power spectral density, autocorrelation and residual mean square angle analysis, we found that a simple superposition of rotational diffusion on a steady rotary motion is insufficient to describe the observed rotation. We observed two additional rotational components, one fluctuating (0.04-0.6 s) and one oscillating (0.8-7 s). However, the effective rotational diffusion coefficient obtained after taking these two components into account generally exceeded that calculated from external friction by two orders of magnitude. This is consistent with a model incorporating association and dissociation of force-generating units.

This article has been cited by other articles:

				T. Minamino, Y. Imae, F. Oosawa, Y. Kobayashi, and K. Oosawa Effect of Intracellular pH on Rotational Speed of Bacterial Flagellar Motors J. Bacteriol., February 15, 2003; 185(4): 1190 - 1194. [Abstract] [Full Text] [PDF]