Journal article

Publication year: 2017

Pages: 6340-6345

Journal: Proceedings of the National Academy of Sciences

Volume number: 114

Issue number: 24

ISSN: 0027-8424

Open access status: Green

DOI Link: https://doi.org/10.1073/pnas.1701644114

Publisher: National Academy of Sciences

Abstract: 
Many bacterial species swim by rotating single polar helical flagella. Depending on the direction of rotation, they can swim forward or backward and change directions to move along chemical gradients but also to navigate their obstructed natural environment in soils, sediments, or mucus. When they get stuck, they naturally try to back out, but they can also resort to a radically different flagellar mode, which we discovered here. Using high-speed microscopy, we monitored the swimming behavior of the monopolarly flagellated species Shewanella putrefaciens with fluorescently labeled flagellar filaments at an agarose-glass interface. We show that, when a cell gets stuck, the polar flagellar filament executes a polymorphic change into a spiral-like form that wraps around the cell body in a spiral-like fashion and enables the cell to escape by a screw-like backward motion. Microscopy and modeling suggest that this propagation mode is triggered by an instability of the flagellum under reversal of the rotation and the applied torque. The switch is reversible and bacteria that have escaped the trap can return to their normal swimming mode by another reversal of motor direction. The screw-type flagellar arrangement enables a unique mode of propagation and, given the large number of polarly flagellated bacteria, we expect it to be a common and widespread escape or motility mode in complex and structured environments.

Harvard Citation style: Kühn, M., Schmidt, F., Eckhardt, B. and Thormann, K. (2017) Bacteria exploit a polymorphic instability of the flagellar filament to escape from traps, Proceedings of the National Academy of Sciences, 114(24), pp. 6340-6345. https://doi.org/10.1073/pnas.1701644114

APA Citation style: Kühn, M., Schmidt, F., Eckhardt, B., & Thormann, K. (2017). Bacteria exploit a polymorphic instability of the flagellar filament to escape from traps. Proceedings of the National Academy of Sciences. 114(24), 6340-6345. https://doi.org/10.1073/pnas.1701644114