{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"institution":[{"name":"bioRxiv"}],"indexed":{"date-parts":[[2026,5,16]],"date-time":"2026-05-16T17:08:17Z","timestamp":1778951297567,"version":"3.51.4"},"posted":{"date-parts":[[2026,5,13]]},"group-title":"Microbiology","reference-count":74,"publisher":"openRxiv","license":[{"start":{"date-parts":[[2026,5,13]],"date-time":"2026-05-13T00:00:00Z","timestamp":1778630400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/www.biorxiv.org\/about\/FAQ#license"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"accepted":{"date-parts":[[2026,5,13]]},"abstract":"<jats:title>ABSTRACT<\/jats:title>\n                <jats:p>\n                  The transmembrane export apparatus is a conserved core of bacterial type III secretion systems, shared by the flagellum and injectisome. Powered by the proton-motive force (PMF), this machinery translocates protein substrates across the bacterial envelope to support motility and virulence. However, its assembly and operation within native membranes remain poorly understood. Here, using\n                  <jats:italic>in-situ<\/jats:italic>\n                  single-particle cryo-electron microscopy, we resolve near-atomic-resolution structures of the flagellar export apparatus within the periplasmic flagellar motor of the Lyme disease spirochete\n                  <jats:italic>Borrelia burgdorferi<\/jats:italic>\n                  . Structural and genetic analyses suggest that coordinated, stepwise assembly of the flagellar export apparatus and MS-ring drives local deformation of the cytoplasmic membrane through extensive protein-lipid-protein interactions, constructing a funnel-shaped conduit optimal for substrate translocation. In addition, a conserved hydrophilic pathway lies within core export protein FlhA, with key acidic residues essential for export activity and supporting PMF-driven substrate translocation. Together, these findings establish a mechanistic framework for export apparatus assembly and energy transduction, defining core principles of type III secretion.\n                <\/jats:p>","DOI":"10.64898\/2026.05.13.724734","type":"posted-content","created":{"date-parts":[[2026,5,14]],"date-time":"2026-05-14T05:25:14Z","timestamp":1778736314000},"source":"Crossref","is-referenced-by-count":0,"title":["<i>In-situ<\/i>\n                  structure of the flagellar export apparatus in\n                  <i>Borrelia burgdorferi<\/i>"],"prefix":"10.64898","author":[{"given":"Jian","family":"Yue","sequence":"first","affiliation":[{"name":"Department of Microbial Pathogenesis, Yale School of Medicine, New Haven, CT 06516, USA"},{"name":"Microbial Sciences Institute, Yale University, West Haven, CT 06536, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Akarsh","family":"Manne","sequence":"additional","affiliation":[{"name":"Department of Microbiology and Immunology, Brody School of Medicine, East Carolina University, Greenville, NC 27834, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5398-4910","authenticated-orcid":false,"given":"Wangbiao","family":"Guo","sequence":"additional","affiliation":[{"name":"Department of Microbial Pathogenesis, Yale School of Medicine, New Haven, CT 06516, USA"},{"name":"Microbial Sciences Institute, Yale University, West Haven, CT 06536, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Huaxin","family":"Yu","sequence":"additional","affiliation":[{"name":"Department of Microbial Pathogenesis, Yale School of Medicine, New Haven, CT 06516, USA"},{"name":"Microbial Sciences Institute, Yale University, West Haven, CT 06536, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jiaqi","family":"Wang","sequence":"additional","affiliation":[{"name":"Department of Microbial Pathogenesis, Yale School of Medicine, New Haven, CT 06516, USA"},{"name":"Microbial Sciences Institute, Yale University, West Haven, CT 06536, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Md Khalesur","family":"Rahman","sequence":"additional","affiliation":[{"name":"Department of Microbiology and Immunology, Brody School of Medicine, East Carolina University, Greenville, NC 27834, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Kathryn","family":"Lees","sequence":"additional","affiliation":[{"name":"Department of Microbiology and Immunology, Brody School of Medicine, East Carolina University, Greenville, NC 27834, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Hui","family":"Xu","sequence":"additional","affiliation":[{"name":"Department of Microbiology and Immunology, Brody School of Medicine, East Carolina University, Greenville, NC 27834, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jack M.","family":"Botting","sequence":"additional","affiliation":[{"name":"Department of Microbial Pathogenesis, Yale School of Medicine, New Haven, CT 06516, USA"},{"name":"Microbial Sciences Institute, Yale University, West Haven, CT 06536, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Md A.","family":"Motaleb","sequence":"additional","affiliation":[{"name":"Department of Microbiology and Immunology, Brody School of Medicine, East Carolina University, Greenville, NC 27834, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jun","family":"Liu","sequence":"additional","affiliation":[{"name":"Department of Microbial Pathogenesis, Yale School of Medicine, New Haven, CT 06516, USA"},{"name":"Microbial Sciences Institute, Yale University, West Haven, CT 06536, USA"},{"name":"Department of Cell Biology, Yale School of Medicine, New Haven, CT 06510, USA"},{"name":"Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06511, 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