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Effects of shear-thinning viscosity and viscoelastic stresses on flagellated bacteria motility

Qu, Zijie and Breuer, Kenneth S. (2020) Effects of shear-thinning viscosity and viscoelastic stresses on flagellated bacteria motility. Physical Review Fluids, 5 (7). Art. No. 073103. ISSN 2469-990X. doi:10.1103/physrevfluids.5.073103.

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The behavior of flagellated bacteria swimming in non-Newtonian media remains an area with contradictory and conflicting results. We report on the behavior of wild-type and smooth-swimming E. coli in Newtonian, shear-thinning, and viscoelastic media, measuring their trajectories and swimming speed using a three-dimensional real-time tracking microscope. We conclude that the speed enhancement in Methocel solution at higher concentrations is due to shear thinning and an analytical model is used to support our experimental result. We argue that shear-induced normal stresses reduce wobbling behavior during cell swimming but do not significantly affect swimming speed. However, the normal stresses play an important role in decreasing the flagellar bundling time, which changes the swimming-speed distribution. A dimensionless number, the “strangulation number” (Str) is proposed and used to characterize this effect.

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Additional Information:© 2020 American Physical Society. (Received 5 April 2019; accepted 2 June 2020; published 10 July 2020) We are grateful to the Coli Genetic Stock Center (Yale University) and to Howard Berg for bacterial strains and advice. We thank Anubhav Tripathi for help in measuring the fluid viscosities. A special thanks is due to Saverio Spagnolie, who provided considerable insight into the modeling of the filament in a viscoelastic fluid and who suggested the name “strangulation number.” This work was supported by the National Science Foundation (CBET 1336638).
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Issue or Number:7
Record Number:CaltechAUTHORS:20200723-122439017
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:104532
Deposited By: George Porter
Deposited On:24 Jul 2020 15:50
Last Modified:16 Nov 2021 18:32

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