title: The flat-ribbon configuration of the periplasmic flagella of Borrelia burgdorferi and its relationship to motility and morphology.
abstract: Electron cryotomography was used to analyze the structure of the Lyme disease spirochete, Borrelia burgdorferi. This methodology offers a new means for studying the native architecture of bacteria by eliminating the chemical fixing, dehydration, and staining steps of conventional electron microscopy. Using electron cryotomography, we noted that membrane blebs formed at the ends of the cells. These blebs may be precursors to vesicles that are released from cells grown in vivo and in vitro. We found that the periplasmic space of B. burgdorferi was quite narrow (16.0 nm) compared to those of Escherichia coli and Pseudomonas aeruginosa. However, in the vicinity of the periplasmic flagella, this space was considerably wider (42.3 nm). In contrast to previous results, the periplasmic flagella did not form a bundle but rather formed a tight-fitting ribbon that wraps around the protoplasmic cell cylinder in a right-handed sense. We show how the ribbon configuration of the assembled periplasmic flagella is more advantageous than a bundle for both swimming and forming the flat-wave morphology. Previous results indicate that B. burgdorferi motility is dependent on the rotation of the periplasmic flagella in generating backward-moving waves along the length of the cell. This swimming requires that the rotation of the flagella exerts force on the cell cylinder. Accordingly, a ribbon is more beneficial than a bundle, as this configuration allows each periplasmic flagellum to have direct contact with the cell cylinder in order to exert that force, and it minimizes interference between the rotating filaments.
authors.affiliation: Department of Microbiology, Immunology and Cell Biology, Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, West Virginia 26506-9177, USA. ncharon@hsc.wvu.edu
authors.forename: Nyles W
authors.initials: NW
authors.lastname: Charon
authors.forename: Stuart F
authors.initials: SF
authors.lastname: Goldstein
authors.forename: Michael
authors.initials: M
authors.lastname: Marko
authors.forename: Chyongere
authors.initials: C
authors.lastname: Hsieh
authors.forename: Linda L
authors.initials: LL
authors.lastname: Gebhardt
authors.forename: M Abdul
authors.initials: MA
authors.lastname: Motaleb
authors.forename: Charles W
authors.initials: CW
authors.lastname: Wolgemuth
authors.forename: Ronald J
authors.initials: RJ
authors.lastname: Limberger
authors.forename: Nancy
authors.initials: N
authors.lastname: Rowe
mesh_terms: D025065:Borrelia burgdorferi / Q000737:chemistry* / Q000502:physiology* / Q000648:ultrastructure; D005407:Flagella / Q000737:chemistry* / Q000502:physiology / Q000648:ultrastructure; D006801:Humans; D008193:Lyme Disease / Q000382:microbiology*; D019897:Periplasm / Q000737:chemistry* / Q000502:physiology / Q000648:ultrastructure