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Twin-arginine translocation in Yersinia: the substrates and their role in virulence
Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR). Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS). Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Pathogenic Yersinia cause a manifold of diseases in humans ranging from mild gastroenteritis (Y. pseudotuberculosis and Y. enterocolitica) to pneumonic and bubonic plague (Y. pestis), while all three have a common virulence strategy that relies on a well-studied type III secretion system and its effector proteins to colonize the host and evade immune responses. However, the role of other protein secretion and/or translocation systems in virulence of Yersinia species is not well known. In this thesis, we sought to investigate the contribution of twin-arginine translocation (Tat) pathway and its secreted substrates to the physiology and virulence of Y. pseudotuberculosis. Tat pathway uniquely exports folded proteins including virulence factors across the cytoplasmic membranes of bacteria. The proteins exported by Tat pathway contain a highly conserved twin-arginine motif in the N-terminal signal peptide. We found that the loss of Tat pathway causes a drastic change of the transcriptome of Y. pseudotuberculosis in stationary phase at environmental temperature with differential regulation of genes involved in virulence, carbon metabolism and stress responses. Phenotypic analysis revealed novel phenotypes of the Tat-deficient strain with defects in iron acquisition, acid resistance, copper oxidation and envelope integrity, which we were partly able to associate with the related Tat substrates. Moreover, increased glucose consumption and accumulation of intracellular fumarate were observed in response to inactivation of Tat pathway implicating a generic effect in cellular physiology. We evaluated the direct role of 22 in silico predicted Tat substrate mutants in the mouse infection model and found only one strain, ΔsufI, exhibited a similar degree of attenuation as Tat-deficient strain. Comparative in vivo characterization studies demonstrated a minor defect for ΔsufI in colonization of intestinal tissues compared to the Tat-deficient strain during early infection, whereas both SufI and TatC were required for dissemination from mesenteric lymph nodes and further systemic spread during late infection. This verifies that SufI has a major role in attenuation seen for the Tat deficient strain both during late infection and initial colonization. It is possible that other Tat substrates such as those involved in iron acquisition and copper resistance also has a role in establishing infection. Further phenotypic analysis indicated that SufI function is required for cell division and stress-survival. Transcriptomic analysis revealed that the highest number of differentially regulated genes in response to loss of Tat and SufI were involved in metabolism and transport. Taken together, this thesis presents a thorough analysis of the involvement of Tat pathway in the overall physiology and virulence strategies of Y. pseudotuberculosis. Finally, we propose that strong effects in virulence render TatC and SufI as potential targets for development of novel antimicrobial compounds

Place, publisher, year, edition, pages
Umeå: Umeå University , 2016. , 73 p.
Keyword [en]
Yersinia pseudotuberculosis, Tat, virulence, Tat substrates, SufI, stress response, metabolism, infection, transcriptome analysis
National Category
Biochemistry and Molecular Biology Bioinformatics and Systems Biology Microbiology
Research subject
Infectious Diseases; Molecular Biology; Microbiology
Identifiers
URN: urn:nbn:se:umu:diva-128090ISBN: 978-91-7601-607-7OAI: oai:DiVA.org:umu-128090DiVA: diva2:1048949
Public defence
2016-12-16, Major Groove, Biomedicinhuset, Byggnad 6L, Umeå, 10:00 (English)
Opponent
Supervisors
Available from: 2016-11-25 Created: 2016-11-22 Last updated: 2016-11-23Bibliographically approved
List of papers
1. Transcriptomic and phenotypic analysis reveals new functions for the Tat pathway in Yersinia pseudotuberculosis
Open this publication in new window or tab >>Transcriptomic and phenotypic analysis reveals new functions for the Tat pathway in Yersinia pseudotuberculosis
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2016 (English)In: Journal of Bacteriology, ISSN 0021-9193, E-ISSN 1098-5530, Vol. 198, no 20, 2876-2886 p.Article in journal (Refereed) Published
Abstract [en]

The Twin-arginine translocation (Tat) system mediates secretion of folded proteins that in bacteria, plants and archaea are identified via an N-terminal signal peptide. Tat systems are associated with virulence in many bacterial pathogens and our previous studies revealed that Tat deficient Yersinia pseudotuberculosis was severely attenuated for virulence. Aiming to identify Tat-dependent pathways and phenotypes of relevance for in vivo infection, we analysed the global transcriptome of parental and ∆tatC mutant strains of Y. pseudotuberculosis during exponential and stationary growth at 26oC and 37oC. The most significant changes in the transcriptome of the ∆tatC mutant were seen at 26oC during stationary phase growth and these included the altered expression of genes related to virulence, stress responses and metabolism. Subsequent phenotypic analysis based on these transcriptome changes revealed several novel Tat-dependent phenotypes including decreased YadA expression, impaired growth under iron-limiting and high copper conditions as well as acidic pH and SDS. Several functionally related Tat substrates were also verified to contribute to these phenotypes. Interestingly, the phenotypic defects observed in the Tat-deficient strain were generally more pronounced than in mutants lacking the Tat substrate predicted to contribute to that specific function. Altogether, this provides new insight into the impact of Tat deficiency on in vivo fitness and survival/replication of Y. pseudotuberculosis during infection.

Place, publisher, year, edition, pages
Washington: American Society for Microbiology, 2016
Keyword
Yersinia pseudotuberculosis, Tat pathway, virulence, stress response, transcriptome analysis
National Category
Microbiology Bioinformatics and Systems Biology Biochemistry and Molecular Biology
Research subject
Infectious Diseases; Microbiology; Molecular Biology
Identifiers
urn:nbn:se:umu:diva-128029 (URN)10.1128/JB.00352-16 (DOI)000384347500014 ()
Available from: 2016-11-22 Created: 2016-11-22 Last updated: 2016-11-23Bibliographically approved
2. The Tat substrate SufI is critical for the ability of Yersinia pseudotuberculosis to cause systemic infection
Open this publication in new window or tab >>The Tat substrate SufI is critical for the ability of Yersinia pseudotuberculosis to cause systemic infection
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(English)Manuscript (preprint) (Other academic)
National Category
Microbiology Immunology
Identifiers
urn:nbn:se:umu:diva-128087 (URN)
Available from: 2016-11-22 Created: 2016-11-22 Last updated: 2016-11-23
3. Transcriptomic and phenotypic analysis of sufI and tatC mutants of Yersinia pseudotuberculosis
Open this publication in new window or tab >>Transcriptomic and phenotypic analysis of sufI and tatC mutants of Yersinia pseudotuberculosis
(English)Manuscript (preprint) (Other academic)
National Category
Microbiology Biochemistry and Molecular Biology Bioinformatics and Systems Biology
Identifiers
urn:nbn:se:umu:diva-128089 (URN)
Available from: 2016-11-22 Created: 2016-11-22 Last updated: 2016-11-23

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