Campylobacter jejunimotility integrates specialized cell shape, flagellar filament, and motor, to coordinate action of its opposed flagella

Author summary Campylobacter jejuniis a leading cause of gastroenteritis worldwide. This species uses its helical body and opposing flagella to drill its way through the viscous mucosa of host organisms' gastrointestinal tracts. In this work, we show thatC.jejunicoordinates its two opposing flagella by wrapping the leading flagellum around the cell body when swimming in viscous environments. We also provide evidence that the helical cell body ofC.jejuniand its composite flagellar filament are important for wrapping and unwrapping of the flagellar filament during reversals of swimming direction. Campylobacter jejunirotates a flagellum at each pole to swim through the viscous mucosa of its hosts' gastrointestinal tracts. Despite their importance for host colonization, however, howC.jejunicoordinates rotation of these two opposing flagella is unclear. As well as their polar placement,C.jejuni'sflagella deviate from the norm of Enterobacteriaceae 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 howC.jejuni'sopposed motors coordinate, and what contribution these factors play inC.jejunimotility, we developed strains with flagella that could be fluorescently labeled, and observed them by high-speed video microscopy. We found thatC.jejunicoordinates its dual flagella by wrapping the leading filament around the cell body during swimming in high-viscosity media and that its differentiated flagellar filament and helical body have evolved to facilitate this wrapped-mode swimming.