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arXiv · 1011.2438

Force-extension curves of bacterial flagella

Reinhard Vogel·Holger Stark
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Abstract

Bacterial flagella assume different helical shapes during the tumbling phase of a bacterium but also in response to varying environmental conditions. Force-extension measurements by Darnton and Berg explicitly demonstrate a transformation from the coiled to the normal helical state [N.C. Darnton and H.C. Berg, Biophys. J. {92}, 2230 (2007)]. We here develop an elastic model for the flagellum based on Kirchhoff's theory of an elastic rod that describes such a polymorphic transformation and use resistive force theory to couple the flagellum to the aqueous environment. We present Brownian dynamics simulations that quantitatively reproduce the force-extension curves and study how the ratio $Γ$ of torsional to bending rigidity and the extensional rate influence the response of the flagellum. An upper bound for $Γ$ is given. Using clamped flagella, we show in an adiabatic approximation that the mean extension, where a local coiled-to-normal transition occurs first, depends on the logarithm of the extensional rate.

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Reinhard Vogel, Holger Stark. 2010-11-10. Force-extension curves of bacterial flagella. https://doi.org/10.1140/epje%2Fi2010-10664-5

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