Year: 2026
Type: preprint
Abstract: Motile bacteria must continuously adjust their motility to navigate and colonize diverse environments, including mammalian hosts, yet the underlying mechanisms remain poorly understood. Here, using in situ single-particle cryo-electron microscopy, we determine near-atomic structures of the flagellar motor in the Lyme disease spirochete Borrelia burgdorferi and uncover a novel mechanism for controlling torque generation. We identify a distinct neutral state in which individual torque-generating MotA 5 B 2 stator complexes remain incorporated in the motor but adopt an extended, tilted conformation disengaged from the rotor. Two conserved flagellar proteins, FliL and FlcA, form a transmembrane scaffold that retains 16 stator complexes, while FapA, a newly identified multidomain flagellar protein, binds the cytoplasmic base of the stator complex and stabilizes its rotor-disengaged conformation. Strikingly, rotor-engaged and rotor-disengaged stators coexist within individual motors, demonstrating that stator retention and torque engagement are separable states. Our findings establish a motor-retained neutral stator state and reveal a molecular-clutch mechanism that independently controls the engagement of individual stator units with the rotor, enabling rapid and precise regulation of flagellar torque and motility.
Language: English
Subfield: Genetics
Domain: Life Sciences
Open Access status: green
Awards: Exploring new virulence factors of the oral spirochete Treponema denticola, Delineation of unique flagellar proteins in spirochetes, Decoding the glycome of oral Treponema denticola, Structure-Function Relationships in the Spirochetal Flagellar Motor, Understanding Unique Aspects of Motility and Chemotaxis in Borrelia burgdorferi
OpenAlex ID: W7222041385