Identification of Viscosity-Dependent Determinants of Campylobacter jejuni That Impact the Velocity of Flagellar Motility

Campylobacter jejuni readily colonizes the thick mucus layer lining the lower intestinal epithelium of hosts to promote commensalism in birds and animals or diarrheal disease in humans. A few studies have observed C. jejuni swimming velocity to increase upon an increase in the viscosity of the environment, which is in sharp contrast to many other motile bacteria. This high swimming velocity in viscous environments is likely beneficial for C. jejuni to penetrate and maintain a presence in the intestinal mucus layer of hosts. C. jejuni produces one of the most structurally complex bacterial flagellar motors that has been proposed to generate high torque for high velocity of motility. However, it is not known how this flagellar motor alters output to impact swimming velocities in a viscosity-dependent manner. We used a suppressor mutant screen to identify these determinants and found a gene we believe encodes a brake or clutch to reduce flagellar motor output and swimming velocity in low viscosity conditions.