{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"institution":[{"name":"bioRxiv"}],"indexed":{"date-parts":[[2026,7,30]],"date-time":"2026-07-30T15:17:18Z","timestamp":1785424638528,"version":"3.56.0"},"posted":{"date-parts":[[2026,5,30]]},"group-title":"Microbiology","reference-count":82,"publisher":"openRxiv","license":[{"start":{"date-parts":[[2026,5,30]],"date-time":"2026-05-30T00:00:00Z","timestamp":1780099200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/www.biorxiv.org\/about\/FAQ#license"}],"funder":[{"award":["R01AI132818"],"award-info":[{"award-number":["R01AI132818"]}],"id":[{"id":"https:\/\/ror.org\/01cwqze88","id-type":"ROR","asserted-by":"publisher"}]},{"award":["R01AI087946"],"award-info":[{"award-number":["R01AI087946"]}],"id":[{"id":"https:\/\/ror.org\/01cwqze88","id-type":"ROR","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"accepted":{"date-parts":[[2026,5,30]]},"abstract":"<jats:title>Abstract<\/jats:title>\n                <jats:p>\n                  Periplasmic flagella are essential for the distinctive morphology and motility of the Lyme disease spirochete\n                  <jats:italic>Borrelia burgdorferi<\/jats:italic>\n                  , and motility plays a critical role in its pathogenic lifestyle. These flagella are powered by specialized motors that contain a large spirochete-specific multiprotein collar complex, yet the molecular architecture and mechanisms underlying high-torque motility remain poorly understood. Here, we identify the tetratricopeptide repeat (TPR)-containing protein BB0298 as a previously unrecognized flagellar collar component and rename it FlcE. Loss of\n                  <jats:italic>flcE<\/jats:italic>\n                  results in altered morphology and nearly abolishes the spirochete\u2019s motility. Using cryo-electron tomography and biochemical analyses, we show that FlcE occupies a unique position within the collar where it surrounds the FliL-stator complex by binding to FliL and the collar protein FlcA. These findings support a model in which FlcE functions as a molecular \u201clatch\u201d that secures stator assemblies to sustain efficient torque generation. Notably,\n                  <jats:italic>flcE<\/jats:italic>\n                  is conserved across most motile members of the Spirochaetales and is located within the division and cell-wall (\n                  <jats:italic>dcw<\/jats:italic>\n                  ) gene cluster. More broadly, the conservation of TPR-containing structural proteins across diverse bacterial flagellar systems suggests a general architectural principle whereby dedicated scaffolds reinforce stator complexes to maximize motor performance under high mechanical loads.\n                <\/jats:p>\n                <jats:sec>\n                  <jats:title>Importance<\/jats:title>\n                  <jats:p>\n                    Spirochetal motility requires the stable engagement of torque-generating stator units, yet the mechanisms that secure these complexes have remained unknown. Here, we identify FlcE as a previously unrecognized collar protein that functions as a molecular latch by restraining the FliL-stator complex. Loss of FlcE destabilizes FliL-stator assemblies and severely impairs motility, demonstrating that peripheral scaffolding is essential for sustaining high torque output in the Lyme disease spirochete\n                    <jats:italic>Borrelia burgdorferi<\/jats:italic>\n                    . The conservation of tetratricopeptide repeat domains in FlcE and other bacterial flagellar proteins further suggests a broader mechanism in which specialized scaffolds anchor and stabilize stator complexes, enabling high torque generation. Because motility is a central virulence determinant in many pathogenic bacteria\u2014including\n                    <jats:italic>B. burgdorferi<\/jats:italic>\n                    during transmission from the tick to the mammalian host and subsequent infection\u2014defining the mechanistic role of FlcE provides important insight into the molecular basis of motility-driven pathogenesis and suggests new strategies for disrupting bacterial infection.\n                  <\/jats:p>\n                <\/jats:sec>","DOI":"10.64898\/2026.05.29.728556","type":"posted-content","created":{"date-parts":[[2026,5,31]],"date-time":"2026-05-31T04:50:14Z","timestamp":1780203014000},"source":"Crossref","is-referenced-by-count":0,"title":["FlcE latches onto the FliL-stator complex to turbocharge flagellar motility in\n                  <i>Borrelia burgdorferi<\/i>"],"prefix":"10.64898","author":[{"given":"Md Khalesur","family":"Rahman","sequence":"first","affiliation":[{"name":"Department of Microbiology & Immunology, Brody School of Medicine, East Carolina University, Greenville, NC 27834, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"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":[{"vocabulary":"crossref","role":"author"}]},{"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":[{"vocabulary":"crossref","role":"author"}]},{"given":"Michael Y.","family":"Galperin","sequence":"additional","affiliation":[{"name":"Division of Intramural Research, National Library of Medicine, National Institutes of Health, Bethesda, MD 20894, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"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, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Md A.","family":"Motaleb","sequence":"additional","affiliation":[{"name":"Department of Microbiology & Immunology, Brody School of Medicine, East Carolina University, Greenville, NC 27834, 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