title: AphA and LuxR/HapR reciprocally control quorum sensing in vibrios.
abstract: Bacteria cycle between periods when they perform individual behaviors and periods when they perform group behaviors. These transitions are controlled by a cell-cell communication process called quorum sensing, in which extracellular signal molecules, called autoinducers (AIs), are released, accumulate, and are synchronously detected by a group of bacteria. AI detection results in community-wide changes in gene expression, enabling bacteria to collectively execute behaviors such as bioluminescence, biofilm formation, and virulence factor production. In this study, we show that the transcription factor AphA is a master regulator of quorum sensing that operates at low cell density (LCD) in Vibrio harveyi and Vibrio cholerae. In contrast, LuxR (V. harveyi)/HapR (V. cholerae) is the master regulator that operates at high cell density (HCD). At LCD, redundant small noncoding RNAs (sRNAs) activate production of AphA, and AphA and the sRNAs repress production of LuxR/HapR. Conversely, at HCD, LuxR/HapR represses aphA. This network architecture ensures maximal AphA production at LCD and maximal LuxR/HapR production at HCD. Microarray analyses reveal that 300 genes are regulated by AphA at LCD in V. harveyi, a subset of which is also controlled by LuxR. We propose that reciprocal gradients of AphA and LuxR/HapR establish the quorum-sensing LCD and HCD gene expression patterns, respectively.
authors.affiliation: Department of Molecular Biology, Princeton University, Princeton, New Jersey 08544, USA.
authors.forename: Steven T
authors.initials: ST
authors.lastname: Rutherford
authors.forename: Julia C
authors.initials: JC
authors.lastname: van Kessel
authors.forename: Yi
authors.initials: Y
authors.lastname: Shao
authors.forename: Bonnie L
authors.initials: BL
authors.lastname: Bassler
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D001483:Base Sequence; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D046228:Microarray Analysis; D008954:Models, Biological; D008969:Molecular Sequence Data; D053038:Quorum Sensing / Q000235:genetics* / Q000502:physiology; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D012689:Sequence Homology, Nucleic Acid; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D014733:Vibrio / Q000235:genetics / Q000378:metabolism / Q000502:physiology*
chemical_list: C501058:AphA protein, Vibrio cholerae; D001426:Bacterial Proteins; D012097:Repressor Proteins; D015534:Trans-Activators; C064778:LuxR autoinducer binding proteins