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Appl. Environ. Microbiol., Sep 1997, 3474-3479, Vol 63, No. 9
MA Vigeant and RM Ford
Escherichia coli bacteria have been observed to swim along a glass surface
for several minutes at a time. Settling velocities of nonmotile cells and a
computer simulation of motile cells confirmed that an attractive force kept
the bacteria near the surface. The goal of this study was to evaluate
whether this attractive force could be explained by reversible adhesion of
E. coli to the surface in the secondary energy minimum, according to the
theory of Derjaguin, Landan, Verwey, and Overbeek (DLVO theory). This
theory describes interactions between colloidal particles by combining
attractive van der Waals forces with repulsive electrostatic forces. A
three-dimensional-tracking microscope was used to follow both wild-type and
smooth-swimming E. coli bacteria as they interacted with a glass coverslip
in media of increasing ionic strengths, which corresponded to increasing
depths of the secondary energy minimum. We found no quantifiable changes
with ionic strength for either the tendencies of individual bacteria to
approach the surface or the overall times bacteria spent near the surface.
One change in bacterial behavior which was observed with the change in
ionic strength was that the diameters of the circles which the smooth-
swimming bacteria traced out on the glass increased in low-ionic- strength
solution.
Copyright © 1997, American Society for Microbiology
Interactions between motile Escherichia coli and glass in media with various ionic strengths, as observed with a three-dimensional-tracking microscope
Department of Chemical Engineering, School of Engineering and Applied Science, University of Virginia, Charlottesville 22903, USA.
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