Torque generation and regulation in the flagellar motor of Campylobacter jejuni differ from those of model organisms

Campylobacter jejuni flagellar motors generate an exceptionally high stall torque (~3600 pN·nm) and show an approximately linear torque decline with speed, unlike the biphasic pattern in model bacteria.

• Why it matters: Established biophysical models largely come from Escherichia coli and Salmonella enterica serovar Typhimurium, but structural diversity raises uncertainty about whether their torque–speed behavior and stator regulation apply universally.
• What they did: Single-motor assays measured torque output and stator dynamics in Campylobacter jejuni, including time-resolved tracking of discrete speed changes and inference of active stator units (11 ± 4) from dynamic behavior.
• The result: The inferred active stator units averaged 11 ± 4 (below a 17-unit structural complement), showed no clear dependence on viscous load, and after proton motive force collapse motor activity recovered rapidly, supporting reversible activation of pre-associated stator units.

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