Change search
ReferencesLink to record
Permanent link

Direct link
Type VI secretion modulates quorum sensing and stress response in Vibrio anguillarum.
Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR). Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
Show others and affiliations
2009 (English)In: Environmental Microbiology, ISSN 1462-2912, E-ISSN 1462-2920, Vol. 11, no 12, 3018-3028 p.Article in journal (Refereed) Published
Abstract [en]

Type VI protein secretion systems (T6SS) are essential for virulence of several Gram-negative bacteria. In this study, we identified a T6SS in Vibrio anguillarum, a marine bacterium that causes a hemorrhagic septicemia in fish. A partial operon vtsA-H (vibrio type six secretion) was sequenced and shown to encode eight proteins. VtsE-H are signature proteins found in other T6SSs, while VtsA-D are not associated with T6SS studied so far. In-frame deletions were made in each gene. Secretion of a haemolysin-co-regulated-like protein (Hcp), a protein secreted by all studied T6SSs, was decreased in VtsE-H. Unexpectedly, VtsA, VtsC and VtsD activated while VtsB and VtsE-H repressed hcp expression. The T6SS proteins also regulated expression of two extracellular proteases, EmpA and PrtV, but inversely to Hcp expression. This regulation was indirect as T6S positively regulated expression of the stress-response regulator RpoS and the quorum-sensing regulator VanT, which positively regulate protease expression. Moreover, VtsA-H proteins were not needed for virulence but did play a role in various stress responses. Thus, these data characterize a new role for T6S in the ecology of bacteria and we hypothesize this role to be a signal sensing mechanism that modulates the expression of regulators of the general stress response.

Place, publisher, year, edition, pages
2009. Vol. 11, no 12, 3018-3028 p.
National Category
Microbiology in the medical area
URN: urn:nbn:se:umu:diva-31616DOI: 10.1111/j.1462-2920.2009.02005.xPubMedID: 19624706OAI: diva2:293535
Available from: 2010-02-11 Created: 2010-02-11 Last updated: 2012-08-13Bibliographically approved
In thesis
1. Stress response and virulence in Vibrio anguillarum
Open this publication in new window or tab >>Stress response and virulence in Vibrio anguillarum
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Bacteria use quorum sensing, a cell to cell signaling mechanism mediated by small molecules that are produced by specific signal molecule synthases, to regulate gene expression in response to population density. In Vibrio anguillarum, the quorum-sensing phosphorelay channels information from three hybrid sensor kinases VanN, VanQ, CqsS that sense signal molecules produced by the synthases VanM, VanS and CqsA, onto the phosphotransferase VanU, to regulate activity of the response regulator VanO. VanO activates transcription of quorum-sensing regulatory RNAs (Qrr), which work together with the RNA chaperone Hfq to repress expression of the transcriptional regulator VanT.

The work presented in this thesis characterizes quorum-sensing independent and quorum-sensing dependent mechanisms that regulate VanT expression. Moreover, an in vivo imaging system was established, as a means to study V. anguillarum infections in the rainbow trout infection model.

Two quorum-sensing independent mechanisms regulating VanT expression were identified. First, the sigma factor RpoS indirectly activates VanT expression during transition into stationary growth phase by inhibiting hfq expression. Both, RpoS and VanT are crucial for stress response. Second, a type VI secretion system (T6SS) has a novel function as a signal sensing mechanism to regulate rpoS and vanT expression. Consequently, RpoS, quorum sensing and T6SS form a global network that senses stress and modulates stress response to ensure survival of the bacteria.

Further analysis of the quorum-sensing dependent regulation of VanT expression by the phosphorelay system revealed that four qrr genes are expressed continuously during growth. The phosphotransferase VanU is suggested to activate two response regulators, VanO and a predicted second response regulator. Activated VanO induces expression of the Qrr sRNAs, whereas, the predicted response regulator represses expression of the Qrr sRNAs. Thus, VanU has a pivotal role in the regulation of VanT expression. The signal synthase VanM and VanT form a regulatory loop, in which VanM represses VanT by inducing expression of the Qrr sRNAs and VanT directly activates vanM expression to repress its own expression. Moreover, Hfq destabilizes vanM mRNA, repressing vanM expression. VanT forms another regulatory loop with the transcriptional regulator LuxT, in which LuxT activates vanT expression and VanT directly represses luxT expression.

V. anguillarum is an opportunistic pathogen that causes vibriosis, a terminal hemorrhagic septicemia. The spatial and temporal progression of the infection was analyzed using the whole animal with an in vivo bioluminescent imaging method. Initial studies showed that colonization of the fish skin requires the siderophore, the RNA chaperone Hfq and the exopolysaccharide transport system, which protects against the innate immunity on the skin. Colonization of the fish skin is crucial for disease.

Place, publisher, year, edition, pages
Umeå: Institutionen för molekylärbiologi (Teknisk-naturvetenskaplig fakultet) Umeå Universitet, 2010. 86 p.
Vibrio anguillarum, quorum sensing, Type VI secretion, stress response, virulence, skin colonization
National Category
Biochemistry and Molecular Biology
Research subject
Molecular Biology
urn:nbn:se:umu:diva-33269 (URN)978-91-7264-958-3 (ISBN)
Public defence
2010-05-18, NUS, byggnad 6L, Major Groove, Umeå Universitet, Umeå, 13:00 (English)
Available from: 2010-04-27 Created: 2010-04-20 Last updated: 2011-03-14Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full textPubMed

Search in DiVA

By author/editor
Weber, BarbaraWai, Sun NyuntMilton, Debra L
By organisation
Department of Molecular Biology (Faculty of Science and Technology)Umeå Centre for Microbial Research (UCMR)Department of Molecular Biology (Faculty of Medicine)
In the same journal
Environmental Microbiology
Microbiology in the medical area

Search outside of DiVA

GoogleGoogle Scholar
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Altmetric score

Total: 170 hits
ReferencesLink to record
Permanent link

Direct link