Departament of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, United States; Gonçalo Moniz Institute, Oswaldo Cruz Foundation, Brazilian Ministry of Health, Salvador, Brazil
Megan R Brady
Department of Molecular Biophysics and Biochemistry, Yale School of Medicine, New Haven, United States
Fabiana San Martin
Laboratory of Molecular and Structural Microbiology, Institut Pasteur de Montevideo, Montevideo, Uruguay
Laboratory of Molecular and Structural Microbiology, Institut Pasteur de Montevideo, Montevideo, Uruguay
Zhiguo Shang
Department of Molecular Biophysics and Biochemistry, Yale School of Medicine, New Haven, United States
Jun Liu
Department of Microbial Pathogenesis, School of Medicine, Yale University, New Haven, United States
Mathieu Picardeau
Biology of Spirochetes Unit, Institut Pasteur, Paris, France; Integrative Microbiology of Zoonotic Agents, Department of Microbiology, Institut Pasteur, Paris, France
Departament of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, United States; Gonçalo Moniz Institute, Oswaldo Cruz Foundation, Brazilian Ministry of Health, Salvador, Brazil
Laboratory of Molecular and Structural Microbiology, Institut Pasteur de Montevideo, Montevideo, Uruguay; Integrative Microbiology of Zoonotic Agents, Department of Microbiology, Institut Pasteur, Paris, France
Spirochete bacteria, including important pathogens, exhibit a distinctive means of swimming via undulations of the entire cell. Motility is powered by the rotation of supercoiled 'endoflagella' that wrap around the cell body, confined within the periplasmic space. To investigate the structural basis of flagellar supercoiling, which is critical for motility, we determined the structure of native flagellar filaments from the spirochete Leptospira by integrating high-resolution cryo-electron tomography and X-ray crystallography. We show that these filaments are coated by a highly asymmetric, multi-component sheath layer, contrasting with flagellin-only homopolymers previously observed in exoflagellated bacteria. Distinct sheath proteins localize to the filament inner and outer curvatures to define the supercoiling geometry, explaining a key functional attribute of this spirochete flagellum.
