In situ structure of a bacterial flagellar motor at subnanometre resolution reveals adaptations for increased torque
The bacterial flagellar motor, which spins a helical propeller for propulsion, has undergone evolutionary diversification across bacterial species, often involving the addition of structures associated with increasing torque for motility in viscous environments. Understanding how such structures function and have evolved is hampered by challenges in visualizing motors in situ. Here we developed a Campylobacter jejuni minicell system for in situ cryogenic electron microscopy imaging and single-particle analysis of its motor, one of the most complex flagellar motors known, to subnanometre resolution. Focusing on the large periplasmic structures which are essential for increasing torque, our structural data, interpreted with molecular models, show that the basal disk comprises concentric rings of FlgP. The medial disk is a lattice of PflC with PflD, while the proximal disk is a rim of PflB attached to spokes of PflA. PflAB dimerization is essential for proximal disk assembly, recruiting FliL to scaffold more stator complexes at a wider radius which increases torque. We also acquired insights into universal principles of flagellar torque generation. This in situ approach is broadly applicable to other membrane-residing bacterial molecular machines.
Authors
- Thomas Calcraft (ORCID: https://orcid.org/0000-0002-5716-0270)
- Trishant R. Umrekar (ORCID: https://orcid.org/0000-0003-3138-4185)
- Louie Henderson (ORCID: https://orcid.org/0000-0002-7495-3109)
- Mona Alzheimer (ORCID: https://orcid.org/0000-0002-0094-3987)
- Francesco Pedaci (ORCID: https://orcid.org/0000-0002-4530-3027)
- Cynthia M. Sharma (ORCID: https://orcid.org/0000-0002-2321-9705)
- David R. Hendrixson (ORCID: https://orcid.org/0000-0001-8496-2466)
- Eli J. Cohen (ORCID: https://orcid.org/0000-0001-9265-7517)
- Morgan Beeby (ORCID: https://orcid.org/0000-0001-6413-9835)
- Andrea Nans (ORCID: https://orcid.org/0000-0002-3791-2447)
- Peter B. Rosenthal (ORCID: https://orcid.org/0000-0002-0387-2862)
- Kathrin Froschauer (ORCID: https://orcid.org/0000-0001-5288-4440)
- Sriram G. Garg (ORCID: https://orcid.org/0000-0003-4160-5228)
- Deborah A. Ribardo
- William H. Hoffmann (ORCID: https://orcid.org/0000-0002-6689-2609)
- Ashley L. Nord (ORCID: https://orcid.org/0000-0001-6199-2769)
- Georg Hochberg (ORCID: https://orcid.org/0000-0002-7155-0451)
- Tina Drobnič (ORCID: https://orcid.org/0000-0001-6364-1874)
- Sarah L. Svensson (ORCID: https://orcid.org/0000-0002-3183-6084)
- Nanki Singh
Institutions
- Centre National de la Recherche Scientifique (FR)
- Inserm (FR)
- Philipps University of Marburg (DE)
- MRC Laboratory of Molecular Biology (GB)
- University of Würzburg (DE)
- The Francis Crick Institute (GB)
- Centre de Biologie Structurale (FR)
- Max Planck Institute for Terrestrial Microbiology (DE)
- Imperial College London (GB)
- The University of Texas Southwestern Medical Center (US)
Publication Details
- Journal
- Nature Microbiology
- Published
- 2025-07-01
- DOI
- https://doi.org/10.1038/s41564-025-02012-9
- Citations
- 7
- Primary Topic
- Bacterial Genetics and Biotechnology
- Type
- article
- Field-Weighted Citation Impact
- 12.72
Funders
- Wellcome
- Cancer Research UK
- Human Frontier Science Program
- Deutscher Akademischer Austauschdienst
- Deutsche Forschungsgemeinschaft
- Agence Nationale de la Recherche
- Medical Research Council
- Biotechnology and Biological Sciences Research Council
- National Institute of Allergy and Infectious Diseases