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VanT, a Homologue of Vibrio harveyi LuxR, Regulates Serine, Metalloprotease, Pigment, and Biofilm Production in Vibrio anguillarum
Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
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2002 (English)In: Journal of Bacteriology, ISSN 0021-9193, E-ISSN 1098-5530, Vol. 184, no 6, p. 1617-1629Article in journal (Refereed) Published
Abstract [en]

Vibrio anguillarum possesses at least two N-acylhomoserine lactone (AHL) quorum-sensing circuits, one of which is related to the luxMN system of Vibrio harveyi. In this study, we have cloned an additional gene of this circuit, vanT, encoding a V. harveyi LuxR-like transcriptional regulator. A V. anguillarum ΔvanT null mutation resulted in a significant decrease in total protease activity due to loss of expression of the metalloprotease EmpA, but no changes in either AHL production or virulence. Additional genes positively regulated by VanT were identified from a plasmid-based gene library fused to a promoterless lacZ. Three lacZ fusions (serA::lacZhpdA-hgdA::lacZ, and sat-vps73::lacZ) were identified which exhibited decreased expression in the ΔvanT strain. SerA is similar to 3-phosphoglycerate dehydrogenases and catalyzes the first step in the serine-glycine biosynthesis pathway. HgdA has identity with homogentisate dioxygenases, and HpdA is homologous to 4-hydroxyphenylpyruvate dioxygenases (HPPDs) involved in pigment production. V. anguillarum strains require an active VanT to produce high levels of an l-tyrosine-induced brown color via HPPD, suggesting that VanT controls pigment production. Vps73 and Sat are related to Vibrio cholerae proteins encoded within a DNA locus required for biofilm formation. A V. anguillarum ΔvanT mutant and a mutant carrying a polar mutation in the sat-vps73 DNA locus were shown to produce defective biofilms. Hence, a new member of the V. harveyi LuxR transcriptional activator family has been characterized in V. anguillarum that positively regulates serine, metalloprotease, pigment, and biofilm production.

Place, publisher, year, edition, pages
American Society for Microbiology , 2002. Vol. 184, no 6, p. 1617-1629
National Category
Microbiology Cell and Molecular Biology
Identifiers
URN: urn:nbn:se:umu:diva-4950DOI: 10.1128/JB.184.6.1617-1629.2002ISI: 000174131800014PubMedID: 11872713OAI: oai:DiVA.org:umu-4950DiVA, id: diva2:144261
Available from: 2006-02-15 Created: 2006-02-15 Last updated: 2019-01-24Bibliographically 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. p. 96
Series
Doctoral thesis / Umeå University, Department of Molecular Biology
Keywords
Vibriosis, Vibrio anguillarum, quorum sensing, two-component phosphorelay systems
National Category
Biochemistry and Molecular Biology
Identifiers
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)
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Available from: 2006-02-15 Created: 2006-02-15 Last updated: 2019-01-24Bibliographically approved

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