title: The quorum-sensing molecule autoinducer 2 regulates motility and flagellar morphogenesis in Helicobacter pylori.
abstract: The genome of the gastric pathogen Helicobacter pylori contains a homologue of the gene luxS, which has been shown to be responsible for production of the quorum-sensing signal autoinducer 2 (AI-2). We report here that deletion of the luxS gene in strain G27 resulted in decreased motility on soft agar plates, a defect that was complemented by a wild-type copy of the luxS gene and by the addition of cell-free supernatant containing AI-2. The flagella of the luxS mutant appeared normal; however, in genetic backgrounds lacking any of three flagellar regulators--the two-component sensor kinase flgS, the sigma factor sigma28 (also called fliA), and the anti-sigma factor flgM--loss of luxS altered flagellar morphology. In all cases, the double mutant phenotypes were restored to the luxS+ phenotype by the addition of synthetic 4,5-dihydroxy-2,3-pentanedione (DPD), which cyclizes to form AI-2. Furthermore, in all mutant backgrounds loss of luxS caused a decrease in transcript levels of the flagellar regulator flhA. Addition of DPD to luxS cells induced flhA transcription in a dose-dependent manner. Deletion of flhA in a wild-type or luxS mutant background resulted in identical loss of motility, flagella, and flagellar gene expression. These data demonstrate that AI-2 functions as a secreted signaling molecule upstream of FlhA and plays a critical role in global regulation of flagellar gene transcription in H. pylori.
authors.affiliation: Institute of Molecular Biology, University of Oregon, Eugene, OR 97403, USA.
authors.forename: Bethany A
authors.initials: BA
authors.lastname: Rader
authors.forename: Shawn R
authors.initials: SR
authors.lastname: Campagna
authors.forename: Martin F
authors.initials: MF
authors.lastname: Semmelhack
authors.forename: Bonnie L
authors.initials: BL
authors.lastname: Bassler
authors.forename: Karen
authors.initials: K
authors.lastname: Guillemin
mesh_terms: D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology; D013437:Carbon-Sulfur Lyases / Q000235:genetics / Q000502:physiology; D005407:Flagella / Q000648:ultrastructure*; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial; D005816:Genetic Complementation Test; D016480:Helicobacter pylori / Q000235:genetics / Q000502:physiology*; D006714:Homoserine / Q000031:analogs & derivatives* / Q000502:physiology; D007783:Lactones; D008124:Locomotion; D008565:Membrane Proteins / Q000096:biosynthesis / Q000235:genetics; D009024:Morphogenesis; D010420:Pentanes / Q000378:metabolism; D053038:Quorum Sensing; D012329:RNA, Bacterial / Q000096:biosynthesis / Q000235:genetics; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D014158:Transcription, Genetic
chemical_list: C493138:4,5-dihydroxy-2,3-pentanedione; D001426:Bacterial Proteins; C080688:FlhA protein, Bacteria; D007783:Lactones; D008565:Membrane Proteins; C091088:N-octanoylhomoserine lactone; D010420:Pentanes; D012329:RNA, Bacterial; D012333:RNA, Messenger; D006714:Homoserine; D013437:Carbon-Sulfur Lyases; C117753:LuxS protein, Bacteria