In situ imaging of the bacterial flagellar motor disassembly and assembly processes

Mohammed Kaplan, Poorna Subramanian, Debnath Ghosal, Catherine M. Oikonomou, Sahand Pirbadian, Ruth Starwalt-Lee, Shrawan Kumar Mageswaran, Davi R. Ortega, Jeffrey A. Gralnick, Mohamed Y. El-Naggar, Grant J. Jensen

Research output: Contribution to journalArticle

7 Scopus citations


The self-assembly of cellular macromolecular machines such as the bacterial flagellar motor requires the spatio-temporal synchronization of gene expression with proper protein localization and association of dozens of protein components. In Salmonella and Escherichia coli, a sequential, outward assembly mechanism has been proposed for the flagellar motor starting from the inner membrane, with the addition of each new component stabilizing the previous one. However, very little is known about flagellar disassembly. Here, using electron cryo-tomography and sub-tomogram averaging of intact Legionella pneumophila, Pseudomonas aeruginosa, and Shewanella oneidensis cells, we study flagellar motor disassembly and assembly in situ. We first show that motor disassembly results in stable outer membrane-embedded sub-complexes. These sub-complexes consist of the periplasmic embellished P- and L-rings, and bend the membrane inward while it remains apparently sealed. Additionally, we also observe various intermediates of the assembly process including an inner-membrane sub-complex consisting of the C-ring, MS-ring, and export apparatus. Finally, we show that the L-ring is responsible for reshaping the outer membrane, a crucial step in the flagellar assembly process.

Original languageEnglish (US)
Article numbere100957
JournalEMBO Journal
Issue number14
StatePublished - Jul 15 2019


  • assembly
  • bacterial flagellar motor
  • disassembly
  • electron cryo-tomography
  • in situ imaging

PubMed: MeSH publication types

  • Journal Article
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

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  • Cite this

    Kaplan, M., Subramanian, P., Ghosal, D., Oikonomou, C. M., Pirbadian, S., Starwalt-Lee, R., Mageswaran, S. K., Ortega, D. R., Gralnick, J. A., El-Naggar, M. Y., & Jensen, G. J. (2019). In situ imaging of the bacterial flagellar motor disassembly and assembly processes. EMBO Journal, 38(14), [e100957].