hide
Free keywords:
-
Abstract:
At high cell density, swimming bacteria exhibit collective motility
patterns, self-organized through physical interactions of a however
still debated nature. Although high-density behaviours are frequent in
natural situations, it remained unknown how collective motion affects
chemotaxis, the main physiological function of motility, which enables
bacteria to follow environmental gradients in their habitats. Here, we
systematically investigate this question in the model organism
Escherichia coli, varying cell density, cell length, and suspension
confinement. The characteristics of the collective motion indicate that
hydrodynamic interactions between swimmers made the primary contribution
to its emergence. We observe that the chemotactic drift is moderately
enhanced at intermediate cell densities, peaks, and is then strongly
suppressed at higher densities. Numerical simulations reveal that this
suppression occurs because the collective motion disturbs the
choreography necessary for chemotactic sensing. We suggest that this
physical hindrance imposes a fundamental constraint on high-density
behaviours of motile bacteria, including swarming and the formation of
multicellular aggregates and biofilms.
