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Journal of Bacteriology, May 2000, p. 2793-2801, Vol. 182, No. 10
Rowland Institute for Science, Cambridge,
Massachusetts 02142, and Department of Molecular and Cellular
Biology, Harvard University, Cambridge, Massachusetts 02138
Received 10 January 2000/Accepted 3 March 2000
Bacteria swim by rotating flagellar filaments that are several
micrometers long, but only about 20 nm in diameter. The filaments can
exist in different polymorphic forms, having distinct values of
curvature and twist. Rotation rates are on the order of 100 Hz. In the
past, the motion of individual filaments has been visualized by
dark-field or differential-interference-contrast microscopy, methods
hampered by intense scattering from the cell body or shallow depth of
field, respectively. We have found a simple procedure for fluorescently
labeling cells and filaments that allows recording their motion in real
time with an inexpensive video camera and an ordinary fluorescence
microscope with mercury-arc or strobed laser illumination. We report
our initial findings with cells of Escherichia coli.
Tumbles (events that enable swimming cells to alter course) are
remarkably varied. Not every filament on a cell needs to change its
direction of rotation: different filaments can change directions at
different times, and a tumble can result from the change in direction
of only one. Polymorphic transformations tend to occur in the sequence
normal, semicoiled, curly 1, with changes in the direction of movement
of the cell body correlated with transformations to the semicoiled form.
0021-9193/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Real-Time Imaging of Fluorescent Flagellar
Filaments
*
Corresponding author. Mailing address: Department of
Molecular and Cellular Biology, Harvard University, 16 Divinity
Ave., Cambridge, MA 02138. Phone: (617) 495-0924. Fax: (617) 496-1114. E-mail: hberg{at}biosun.harvard.edu.
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