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Novel transient cytoplasmic rings stabilize assembling bacterial flagellar motors

Kaplan, Mohammed and Oikonomou, Catherine M. and Wood, Cecily R. and Chreifi, Georges and Subramanian, Poorna and Ortega, Davi R. and Chang, Yi-Wei and Beeby, Morgan and Shaffer, Carrie L. and Jensen, Grant J. (2022) Novel transient cytoplasmic rings stabilize assembling bacterial flagellar motors. EMBO Journal, 41 (10). Art. No. e109523. ISSN 0261-4189. PMCID PMC9108667. doi:10.15252/embj.2021109523.

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The process by which bacterial cells build their intricate flagellar motility apparatuses has long fascinated scientists. Our understanding of this process comes mainly from studies of purified flagella from two species, Escherichia coli and Salmonella enterica. Here, we used electron cryo-tomography (cryo-ET) to image the assembly of the flagellar motor in situ in diverse Proteobacteria: Hylemonella gracilis, Helicobacter pylori, Campylobacter jejuni, Pseudomonas aeruginosa, Pseudomonas fluorescens, and Shewanella oneidensis. Our results reveal the in situ structures of flagellar intermediates, beginning with the earliest flagellar type III secretion system core complex (fT3SScc) and MS-ring. In high-torque motors of Beta-, Gamma-, and Epsilon-proteobacteria, we discovered novel cytoplasmic rings that interact with the cytoplasmic torque ring formed by FliG. These rings, associated with the MS-ring, assemble very early and persist until the stators are recruited into their periplasmic ring; in their absence the stator ring does not assemble. By imaging mutants in Helicobacter pylori, we found that the fT3SScc proteins FliO and FliQ are required for the assembly of these novel cytoplasmic rings. Our results show that rather than a simple accretion of components, flagellar motor assembly is a dynamic process in which accessory components interact transiently to assist in building the complex nanomachine.

Item Type:Article
Related URLs:
URLURL TypeDescription ItemData ItemData ItemData ItemData
Kaplan, Mohammed0000-0002-0759-0459
Oikonomou, Catherine M.0000-0003-2312-4746
Wood, Cecily R.0000-0003-1259-3862
Chreifi, Georges0000-0003-4194-1694
Ortega, Davi R.0000-0002-8344-2335
Chang, Yi-Wei0000-0003-2391-473X
Beeby, Morgan0000-0001-6413-9835
Shaffer, Carrie L.0000-0002-7457-7422
Jensen, Grant J.0000-0003-1556-4864
Additional Information:© 2022 The Authors. Received 22 August 2021; Revised 31 January 2022; Accepted 16 February 2022. This project was funded by the NIH (grant R01 AI127401 to G.J.J and NIH P20 GM130456 to C.L.S.) and a Baxter postdoctoral fellowship from Caltech to M.K. Cryo-ET work was performed in the Beckman Institute Resource Center for Transmission Electron Microscopy at the California Institute of Technology. We are grateful to Prof. Marc Erhardt (Humboldt-Universität zu Berlin) for critically reading an initial version of this work. Author contributions: Grant J Jensen: Conceptualization; Resources; Formal analysis; Funding acquisition; Writing—review and editing. Mohammed Kaplan: Conceptualization; Data curation; Formal analysis; Funding acquisition; Investigation; Methodology; Writing—original draft; Writing—review and editing. Catherine M Oikonomou: Formal analysis; Writing—review and editing. Cecily R Wood: Data curation; Methodology; Writing—review and editing. Georges Chreifi: Data curation; Writing—review and editing. Poorna Subramanian: Data curation; Writing—review and editing. Davi R Ortega: Data curation; Writing—review & editing. Yi-Wei Chang: Data curation; Writing—review and editing. Morgan Beeby: Data curation; Writing—review and editing. Carrie Shaffer: Data curation; Funding acquisition; Methodology; Writing—review and editing. In addition to the CRediT author contributions listed above, the contributions in detail are: MK and GJJ designed research. MK, CRW, PS, YWC, MB, and CLS prepared samples. MK, GC, PS, YWC, and MB collected data. MK, CMO, DRO, CLS, and GJJ analyzed data. MK wrote the manuscript and all authors edited it. The authors declare that they have no conflict of interest. Data availability: The following subtomogram averages have been deposited in the Electron Microscopy Data Bank ( under the following accession codes: fully assembled flagellar motor of H. gracilis (EMD-25702;, the MS-complex of H. pylori ΔfliM fliP* (EMD-25703;, the MS-complex of H. pylori fliP* (EMD-25704;, the MS-complex of H. pylori ΔfliQ fliP*, (EMD-25705;
Funding AgencyGrant Number
NIHR01 AI127401
NIHP20 GM130456
Baxter FoundationUNSPECIFIED
Subject Keywords:assembly; bacterial flagellar motor; cryo-ET; high-torque; tomography
Issue or Number:10
PubMed Central ID:PMC9108667
Record Number:CaltechAUTHORS:20220421-311275900
Persistent URL:
Official Citation:Novel transient cytoplasmic rings stabilize assembling bacterial flagellar motors. Mohammed Kaplan, Catherine M Oikonomou, Cecily R Wood, Georges Chreifi, Poorna Subramanian, Davi R Ortega, Yi-Wei Chang, Morgan Beeby, Carrie L Shaffer, Grant J Jensen. The EMBO Journal (2022) 41: e109523;
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:114403
Deposited By: Tony Diaz
Deposited On:25 Apr 2022 17:40
Last Modified:31 May 2022 17:16

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