Near-atomic in situ architecture and membrane-coupled dynamics of the Vibrio cholerae sheathed flagellum.

Abstract

The sheathed flagellum of Vibrio cholerae is a self-assembling membranous organelle that coordinates flagellar assembly, sheath biogenesis, and rapid rotation. Here, we determine in-situ near-atomic structures of the sheathed flagellar motor within intact cells. The motor anchors to the outer membrane through lipidated HL-rings without forming a membrane pore, thereby enabling flagellar assembly to drive sheath formation. Conserved LP-rings function as slide-rotary bushings, permitting high-speed rotation within the bacterial envelope while retaining the ability to constrict and seal the lumen upon flagellar ejection. We further show that stator activation depends on a specific protein-protein interaction rather than peptidoglycan engagement. Together, these findings reveal how the distinctive architecture and dynamics of the sheathed flagellum support V. cholerae motility, environmental survival, and persistent colonization of the human gut.