Bend or Twist? What Plectonemes Reveal about the Mysterious Motility of Spiroplasma

Spiroplasma is a unique, helical bacterium that lacks a cell wall and swims using propagating helix hand inversions. These deformations are likely driven by a set of cytoskeletal filaments, but how remains perplexing. Here, we probe the underlying mechanism using a model where either twist or bend d...

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Bibliographic Details
Published in:Physical review letters 2023-10, Vol.131 (17), p.178401-178401, Article 178401
Main Authors: Ryan, Paul M., Shaevitz, Joshua W., Wolgemuth, Charles W.
Format: Article
Language:English
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Summary:Spiroplasma is a unique, helical bacterium that lacks a cell wall and swims using propagating helix hand inversions. These deformations are likely driven by a set of cytoskeletal filaments, but how remains perplexing. Here, we probe the underlying mechanism using a model where either twist or bend drive spiroplasma's chirality inversions. We show that Spiroplasma should wrap into plectonemes at different values of the length and external viscosity, depending on the mechanism. Then, by experimentally measuring the bending modulus of Spiroplasma and if and when plectonemes form, we show that Spiroplasma's helix hand inversions are likely driven by bending.
ISSN:0031-9007
1079-7114
DOI:10.1103/PhysRevLett.131.178401