“Campylobacter jejuni motility integrates specialized cell shape, flagellar filament, and motor, to coordinate action of its opposed flagella in viscous media”

Campylobacter jejuni rotates a flagellum at each pole to swim through the viscous mucosa of its hosts’ gastrointestinal tracts. Despite their importance for host colonization, however, how C. jejuni coordinates rotation of these two opposing flagella is unclear. As well as their polar placement, C. jejuni’s flagella deviate from the Enterobacteriaceael norm in other ways: their flagellar motors produce much higher torque and their flagellar filament is made of two different zones of two different flagellins. To understand how C. jejuni’s opposed motors coordinate, and what contribution these factors play in C. jejuni motility, we developed strains with flagella that could be fluorescently labeled, and observed them by high-speed video microscopy. We found that C. jejuni coordinates its dual flagella by wrapping the leading filament around the cell body during swimming in high-viscosity media and that its differentiated flagellar filament has evolved to facilitate this wrapped-mode swimming. Unexpectedly, C. jejuni’s helical body is important for facile unwrapping of the flagellar filament from the cell body during switching of swimming trajectory. Our findings demonstrate how multiple facets of C. jejuni’s flagella and cell plan have co-evolved for optimal motility in high-viscosity environments.