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A distinctive dual-channel quorum-sensing system operates in Vibrio anguillarum.
Umeå University, Faculty of Medicine, Molecular Biology.
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2004 (English)In: Molecular Microbiology, ISSN 0950-382X, Vol. 52, no 6, 1677-1689 p.Article in journal (Refereed) Published
Abstract [en]

Many bacterial cells communicate using diffusible signal molecules to monitor cell population density via a process termed quorum sensing. In marine Vibrio species, the Vibrio harveyi-type LuxR protein is a key player in a quorum-sensing phosphorelay cascade, which controls the expression of virulence, symbiotic and survival genes. Previously, we characterized Vibrio anguillarum homologues of LuxR (VanT) and LuxMN (VanMN) and, in this study, we have identified homologues of LuxPQ (VanPQ) and LuxOU (VanOU). In contrast to other Vibrio species, vanT was expressed at low cell density and showed no significant induction as the cell number increased. In addition, although the loss of VanO increased vanT expression, the loss of VanU, unexpectedly, decreased it. Both VanN and VanQ were required for repression of vanT even in a vanU mutant, suggesting an alternative route for VanNQ signal transduction other than via VanU. VanT negatively regulated its own expression by binding and repressing the vanT promoter and by binding and activating the vanOU promoter. The signal relay results in a cellular response as expression of the metalloprotease, empA, was altered similar to that of vanT in all the mutants. Consequently, the V. anguillarum quorum-sensing phosphorelay systems work differently from those of V. harveyi and may be used to limit rather than induce vanT expression.

Place, publisher, year, edition, pages
2004. Vol. 52, no 6, 1677-1689 p.
Keyword [en]
Bacterial Proteins/genetics/*metabolism, DNA; Bacterial/chemistry/isolation & purification, Gene Expression Regulation; Bacterial, Genes; Bacterial, Genes; Reporter, Metalloproteases/biosynthesis, Molecular Sequence Data, Mutation, Phosphoproteins/genetics, Phosphotransferases/genetics, RNA; Bacterial/analysis, RNA; Messenger/analysis, Repressor Proteins/genetics, Sequence Analysis; DNA, Sequence Homology, Signal Transduction, Trans-Activators/genetics, Transcription Factors/genetics, Vibrio/*genetics/growth & development/*physiology, Virulence/genetics, beta-Galactosidase/metabolism
URN: urn:nbn:se:umu:diva-17994DOI: 10.1111/j.1365-2958.2004.04083.xPubMedID: 15186417OAI: diva2:157667
Available from: 2007-11-26 Created: 2007-11-26 Last updated: 2009-10-01Bibliographically approved
In thesis
1. VanT, a central regulator of quorum sensing signalling in Vibrio anguillarum
Open this publication in new window or tab >>VanT, a central regulator of quorum sensing signalling in Vibrio anguillarum
2006 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Many bacteria produce signal molecules that serve in a cell-to-cell communication system termed quorum sensing. This signalling system allows a bacterial population to co-ordinately regulate functions according to their cell number in a defined environment. As bacterial growth progresses towards the stationary phase, signalling molecules accumulate in the growth medium and, above a certain threshold level, regulate the expression of genes involved in diverse functions. Most of the functions monitored by quorum sensing are most beneficial when they are performed as a population than by single cells, such as virulence factor production, biofilm formation, conjugation and bioluminescence.

Vibrio anguillarum is a bacterial pathogen that causes terminal hemorrhagic septicaemia in marine fish. V. anguillarum possesses multiple quorum sensing circuits similar to the LuxI/LuxR and the V. harveyi-type systems. In this study, a characterisation of the quorum sensing-regulated transcriptional activator VanT was made. VanT belongs to the V. harveyi LuxR family of transcriptional regulators, which play a central role in quorum sensing signalling in Vibrio species. VanT was shown to regulate serine, metalloprotease, pigment, exopolysaccharide (EPS) and biofilm production. VanT repressed an EPS locus that plays a critical role in bacterial colonization of the fish integument and virulence.

The V. harveyi-like quorum sensing systems were shown to limit rather than induce vanT expression throughout growth in V. anguillarum. In contrast to homologous proteins in other Vibrio spp., the quorum sensing phosphorelay protein VanU and the response regulator VanO had antagonistic roles in the regulation of vanT expression. Unlike other members of the luxR family, vanT was expressed at low cell density and no significant induction due to quorum sensing regulation was seen.

Interestingly, VanT expression was induced by the alternative sigma factor RpoS as the cells entered stationary phase. RpoS was shown to regulate VanT expression post-transcriptionally by promoting vanT mRNA stability. VanT and RpoS were important for bacterial survival under stress conditions, indicating that VanT is likely an essential factor of V. anguillarum stress response.

Place, publisher, year, edition, pages
Umeå: Molekylärbiologi (Teknisk-naturvetenskaplig fakultet), 2006. 96 p.
Doctoral thesis / Umeå University, Department of Molecular Biology
Vibriosis, Vibrio anguillarum, quorum sensing, two-component phosphorelay systems
National Category
Biochemistry and Molecular Biology
urn:nbn:se:umu:diva-702 (URN)91-7264-022-7 (ISBN)
Public defence
2006-03-10, major groove, 6L, Inst. för Molekylärbiologi, Umeå Universitet, 09:00 (English)
Available from: 2006-02-15 Created: 2006-02-15 Last updated: 2009-10-01Bibliographically approved

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