Helicobacter pyloriFlgV forms a flagellar motor ring structure required for optimal motility

ABSTRACT The bacterium Helicobacter pylori has a large flagellar motor that generates significantly higher torque than the archetypical Escherichia coli motor. To understand how H. pylori navigates the viscous environment of the stomach, it is essential to establish how specific motor components contribute to efficient motility. We show here that the protein FlgV, required for motility in Campylobacter jejuni , forms a novel ring associated with the MS and C rings in H. pylori . Deletion of flgV from H. pylori B128 or a highly motile variant of H. pylori G27 (G27M) resulted in reduced motility in soft agar medium. Based on comparative analyses of in-situ flagellar motor structures of H. pylori wild-type and Δ flgV mutants, the reduced motility of the Δ flgV mutants and the location of the FlgV ring suggest it stabilizes interactions between the MS and C rings and/or plays a role in switching the direction of flagellar rotation. Overall, these results identify a novel motor accessory likely adapted to promote flagellar function for bacterial colonization of high-load environments such as the gastric mucosa.