A flagellar-specific ATPase (FliI) is necessary for flagellar export in Helicobacter pylori

Although flagellar motility is essential for the colonisation of the stomach by Helicobacter pylori, little is known about the regulation of flagellar biosynthesis in this organism. We have identified a gene in H. pylori, designated fliI, whose deduced amino acid sequence revealed extensive homology with the FliI/LcrB/InvC family of proteins which energise the export of flagellar and other virulence factors in several bacterial species. An isogenic mutant of fliI was non-motile and synthesised reduced amounts of flagellin and hook protein subunits. The majority (> 99%) of mutant cells were completely aflagellate. These results suggest that FliI is a novel ATPase involved in flagellar export in H. pylori.