Motility has other interesting effects on cell shape, some
of them arising from the fact that bacteria swim differently
near solid surfaces or through viscous fluids. For
example, the curved cells of Vibrio alginolyticus swim
forward in a straight line but move in circles when
swimming backwards near a flat surface [23,24]. This
behavior occurs in a 50–60 mm zone near a surface, while
beyond this layer the cells swim in straight lines in either
direction [23,24]. In this way, marine microorganisms may
increase the time they remain in contact with nutrientrich
surfaces in an otherwise nutrient-poor environment
[23]. The phenomenon may be general because, surprisingly,
non-tumbling E. coli mutants swim on the righthand
side of thin channel and in clockwise circles when
close to a planar surface [25]. The theoretical impact of
this ‘near-surface motility’ on cell shape has not been
explored in depth, but at least one aspect of bacterial
morphology, cell length, changes the dimensions of
these circular motions, which may, in turn, affect cell
foraging behavior [26
]. Finally, cells with spiral
morphologies appear to move through viscous fluids
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