Motility of Helicobacter pylori is coordinately regulated by the transcriptional activator FlgR, an NtrC homolog

sigma(54) is the subunit of bacterial RNA polymerase that transcribes from promoters with enhancer elements bound by enhancer-binding proteins. By com puter searches of Helicobacter pylori genomic sequences, chromosomal gene d isruption, and RNA analyses, we have identified sigma(54)-recognnzed promot ers that regulate transcription of flagellar basal body and hook genes, as well as the enhancer-binding protein FlgR (flagellum regulator), a transact ivating protein of the NtrC family. We demonstrate that FlgR is required fo r bacterial motility and transcription of five promoters for seven basal bo dy and hook genes, In addition, FlgR acts as a repressor of transcription o f the sigma(28)-regulated flaA flagellin gene promoter, while changes in DN A topology repress transcription of the sigma(54)-regulated flaB flagellin gene promoter. Our data indicate that regulation of flagellar gene expressi on in H. pylori shows similarities with that in enterobacteriaceae and Caul obacter.