title: Architecture of a flagellar apparatus in the fast-swimming magnetotactic bacterium MO-1.
abstract: The bacterial flagellum is a motility organelle that consists of a rotary motor and a helical propeller. The flagella usually work individually or by forming a loose bundle to produce thrust. However, the flagellar apparatus of marine bacterium MO-1 is a tight bundle of seven flagellar filaments enveloped in a sheath, and it has been a mystery as to how the flagella rotate smoothly in coordination. Here we have used electron cryotomography to visualize the 3D architecture of the sheathed flagella. The seven filaments are enveloped with 24 fibrils in the sheath, and their basal bodies are arranged in an intertwined hexagonal array similar to the thick and thin filaments of vertebrate skeletal muscles. This complex and exquisite architecture strongly suggests that the fibrils counter-rotate between flagella in direct contact to minimize the friction of high-speed rotation of individual flagella in the tight bundle within the sheath to enable MO-1 cells to swim at about 300 µm/s.
authors.affiliation: Graduate School of Frontier Biosciences,  Osaka University, Suita, Osaka 565-0871,  Japan.
authors.forename: Juanfang
authors.initials: J
authors.lastname: Ruan
authors.forename: Takayuki
authors.initials: T
authors.lastname: Kato
authors.forename: Claire-Lise
authors.initials: CL
authors.lastname: Santini
authors.forename: Tomoko
authors.initials: T
authors.lastname: Miyata
authors.forename: Akihiro
authors.initials: A
authors.lastname: Kawamoto
authors.forename: Wei-Jia
authors.initials: WJ
authors.lastname: Zhang
authors.forename: Alain
authors.initials: A
authors.lastname: Bernadac
authors.forename: Long-Fei
authors.initials: LF
authors.lastname: Wu
authors.forename: Keiichi
authors.initials: K
authors.lastname: Namba
mesh_terms: D001419:Bacteria / Q000648:ultrastructure*; D018407:Bacterial Physiological Phenomena; D020285:Cryoelectron Microscopy; D055032:Electron Microscope Tomography; D005407:Flagella / Q000502:physiology* / Q000648:ultrastructure*; D021621:Imaging, Three-Dimensional; D060328:Magnetic Phenomena; D009068:Movement / Q000502:physiology; D012399:Rotation