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Elife. 2019 Jan 16;8. pii: e43487. doi: 10.7554/eLife.43487.

The presence and absence of periplasmic rings in bacterial flagellar motors correlates with stator type.

Author information

1
Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, United States.
2
Department of Physics and Astronomy, Biological Sciences, and Chemistry, University of Southern California, Los Angeles, United States.
3
Howard Hughes Medical Institute, California Institute of Technology, Pasadena, United States.

Abstract

The bacterial flagellar motor, a cell-envelope-embedded macromolecular machine that functions as a cellular propeller, exhibits significant structural variability between species. Different torque-generating stator modules allow motors to operate in different pH, salt or viscosity levels. How such diversity evolved is unknown. Here, we use electron cryo-tomography to determine the in situ macromolecular structures of three Gammaproteobacteria motors: Legionella pneumophila, Pseudomonas aeruginosa, and Shewanella oneidensis, providing the first views of intact motors with dual stator systems. Complementing our imaging with bioinformatics analysis, we find a correlation between the motor's stator system and its structural elaboration. Motors with a single H+-driven stator have only the core periplasmic P- and L-rings; those with dual H+-driven stators have an elaborated P-ring; and motors with Na+ or Na+/H+-driven stators have both their P- and L-rings embellished. Our results suggest an evolution of structural elaboration that may have enabled pathogenic bacteria to colonize higher-viscosity environments in animal hosts.

KEYWORDS:

Legionella pneumophila; Pseudomonas aeruginosa; Shewanella oneidensis MR-1; bacterial flagellar motor; electron cryo-tomography; evolution; evolutionary biology; infectious disease; microbiology

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