In situ imaging of bacterial outer membrane projections and associated protein complexes using electron cryo-tomography

Mohammed Kaplan, Georges Chreifi, Lauren Ann Metskas, Janine Liedtke, Cecily R. Wood, Catherine M. Oikonomou, William J. Nicolas, Poorna Subramanian, Lori A. Zacharoff, Yuhang Wang, Yi Wei Chang, Morgan Beeby, Megan J. Dobro, Yongtao Zhu, Mark J. McBride, Ariane Briegel, Carrie L. Shaffer, Grant J. Jensen

Research output: Contribution to journalArticlepeer-review

11 Scopus citations


The ability to produce outer membrane projections in the form of tubular membrane extensions (MEs) and membrane vesicles (MVs) is a widespread phenomenon among diderm bacteria. Despite this, our knowledge of the ultrastructure of these extensions and their associated protein complexes remains limited. Here, we surveyed the ultrastructure and formation of MEs and MVs, and their associated protein complexes, in tens of thousands of electron cryo-tomograms of ~90 bacterial species that we have collected for various projects over the past 15 years (Jensen lab database), in addition to data generated in the Briegel lab. We identified outer MEs and MVs in 13 diderm bacterial species and classified several major ultrastructures: (1) tubes with a uniform diameter (with or without an internal scaffold), (2) tubes with irregular diameter, (3) tubes with a vesicular dilation at their tip, (4) pearling tubes, (5) connected chains of vesicles (with or without neck-like connectors), (6) budding vesicles and nanopods. We also identified several protein complexes associated with these MEs and MVs which were distributed either randomly or exclusively at the tip. These complexes include a secretin-like structure and a novel crown-shaped structure observed primarily in vesicles from lysed cells. In total, this work helps to characterize the diversity of bacterial membrane projections and lays the groundwork for future research in this field.

Original languageEnglish
Article numbere73099
StatePublished - Sep 2021

Bibliographical note

Publisher Copyright:
© Kaplan et al.

ASJC Scopus subject areas

  • General Neuroscience
  • General Biochemistry, Genetics and Molecular Biology
  • General Immunology and Microbiology


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