title: A small-RNA-mediated negative feedback loop controls quorum-sensing dynamics in Vibrio harveyi.
abstract: The bioluminescent marine bacterium Vibrio harveyi uses a cell-to-cell communication process called quorum sensing (QS) to co-ordinate behaviours in response to changes in population density. QS is accomplished through the secretion and detection of extracellular signalling molecules called autoinducers. At the centre of the V. harveyi QS circuit are five small regulatory RNAs called Qrr1-5 which destabilize the mRNA of luxR, encoding LuxR, the master transcriptional regulator of QS target genes. Here we show that LuxR directly activates transcription of qrr2, qrr3 and qrr4, leading to the rapid downregulation of luxR. The LuxR-binding sites in the promoters of qrr2, qrr3 and qrr4 were identified and mutated to determine the consequences of this regulatory loop on QS dynamics. Disruption of the loop delays the transition from high to low cell density, and more significantly, decreases the cell density at which the population reaches a quorum. Our results suggest that feedback is essential for optimizing the dynamics of the transitions between individual and group behaviours.
authors.affiliation: Department of Molecular Biology, Howard Hughes Medical Institute, Princeton, NJ 08544-1014, USA.
authors.forename: Kimberly C
authors.initials: KC
authors.lastname: Tu
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Waters
authors.forename: Sine L
authors.initials: SL
authors.lastname: Svenningsen
authors.forename: Bonnie L
authors.initials: BL
authors.lastname: Bassler
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D004269:DNA, Bacterial / Q000235:genetics; D015536:Down-Regulation; D024202:Electrophoretic Mobility Shift Assay; D025461:Feedback, Physiological; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D011156:Population Density; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D053038:Quorum Sensing; D012329:RNA, Bacterial / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic; D014733:Vibrio / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D012329:RNA, Bacterial; D012333:RNA, Messenger; D012097:Repressor Proteins; D015534:Trans-Activators; C064778:LuxR autoinducer binding proteins