Enhanced bacterial swimming speeds in macromolecular polymer solutions

By A. Zöttl, Julia M. Yeomans. Nature Physics, 2017

126 citations recorded by the source corpus.

The locomotion of swimming bacteria in simple Newtonian fluids can successfully be described within the framework of low-Reynolds-number hydrodynamics1. The presence of polymers in biofluids generally increases the viscosity, which is expected to lead to slower swimming for a constant bacterial motor torque. Surprisingly, however, experiments have shown that bacterial speeds can increase in polymeric fluids2–5. Whereas, for example, artificial helical microswimmers in shear-thinning fluids6 or swimming Caenorhabditis elegans worms in wet granular media7,8 increase their speeds substantially, swimming Escherichia coli bacteria in polymeric fluids show just a small increase in speed at low polymer concentrations, followed by a decrease at higher concentrations2,4. The mechanisms behind this behaviour are currently unclear, and therefore we perform extensive coarse-grained simulations of a bacterium swimming in explicitly modelled solutions of macromolecular polymers of different lengths and densities. We observe an increase of up to 60% in swimming speed with polymer density and demonstrate that this is due to a non-uniform distribution of polymers in the vicinity of the bacterium, leading to an apparent slip. However, this in itself cannot predict the large increase in swimming velocity: coupling to the chirality of the bacterial flagellum is also necessary.Bacteria and other helical microswimmers are known to swim faster in non-Newtonian fluids. Coarse-grained simulations suggest the increase may be due to a polymer depletion effect near the body and flagellum, inducing a slip velocity at the surface.

Subfields: Biomedical Engineering, Condensed Matter Physics, Molecular Biology

View Paper: https://www.semanticscholar.org/paper/81b0caefda6947fa5109ae83bcf6b4afa1a89927

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In Biomedical Engineering

In Condensed Matter Physics

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Citations in the corpus

Microswimming in viscoelastic fluids (2021, background): “[74] hen predicts that the flagellum rotates slower in a polymer solution han in a Newtonian fluid, which is the opposite of the argument based n the viscosity difference for cell body and flagellum from Ref.”