Change search
ReferencesLink to record
Permanent link

Direct link
Link between intraphagosomal biotin and rapid phagosomal escape in Francisella
Umeå University, Faculty of Medicine, Department of Clinical Microbiology, Clinical Bacteriology. Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS).
Show others and affiliations
2012 (English)In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 109, no 44, 18084-18089 p.Article in journal (Refereed) Published
Abstract [en]

Cytosolic bacterial pathogens require extensive metabolic adaptations within the host to replicate intracellularly and cause disease. In phagocytic cells such as macrophages, these pathogens must respond rapidly to nutrient limitation within the harsh environment of the phagosome. Many cytosolic pathogens escape the phagosome quickly (15-60 min) and thereby subvert this host defense, reaching the cytosol where they can replicate. Although a great deal of research has focused on strategies used by bacteria to resist antimicrobial phagosomal defenses and transiently pass through this compartment, the metabolic requirements of bacteria in the phagosome are largely uncharacterized. We previously identified a Francisella protein, FTN_0818, as being essential for intracellular replication and involved in virulence in vivo. We now show that FTN_0818 is involved in biotin biosynthesis and required for rapid escape from the Francisella-containing phagosome (FCP). Addition of biotin complemented the phagosomal escape defect of the FTN_0818 mutant, demonstrating that biotin is critical for promoting rapid escape during the short time that the bacteria are in the phagosome. Biotin also rescued the attenuation of the FTN_0818 mutant during infection in vitro and in vivo, highlighting the importance of this process. The key role of biotin in phagosomal escape implies biotin may be a limiting factor during infection. We demonstrate that a bacterial metabolite is required for phagosomal escape of an intracellular pathogen, providing insight into the link between bacterial metabolism and virulence, likely serving as a paradigm for other cytosolic pathogens.

Place, publisher, year, edition, pages
2012. Vol. 109, no 44, 18084-18089 p.
National Category
Infectious Medicine Microbiology in the medical area
URN: urn:nbn:se:umu:diva-62166DOI: 10.1073/pnas.1206411109ISI: 000311149900081PubMedID: 23071317OAI: diva2:575800
Available from: 2012-12-11 Created: 2012-12-10 Last updated: 2016-05-24Bibliographically approved
In thesis
1. The Francisella pathogenicity island: its role in type VI secretion and intracellular infection
Open this publication in new window or tab >>The Francisella pathogenicity island: its role in type VI secretion and intracellular infection
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Intracellular bacteria have developed various mechanisms to enter and persist in host cells and, at the same time, to evade the host immune response. One such pathogen is Francisella tularensis, the etiological agent of tularemia. After phagocytosis, this Gram-negative bacterium quickly escapes from the phagocytic compartment and replicates in the host cell cytosol. For this mode of infection, several components of the Francisella pathogenicity island (FPI) are critical. Interestingly, some FPI proteins share homology to components of Type VI Secretion Systems (T6SSs), but their assembly and functionality remains to be shown in Francisella.The thesis focused on the characterization of several of these FPI components; more specifically, how they contribute to the infection cycle as well as their possible role in the putative T6SS. We identified three unique mutants, ΔiglG, ΔiglI and ΔpdpE, which to various degrees were able to escape the phagosomal compartment, replicate in the host cytosol and cause host cell cytotoxicity. In contrast, ΔiglE as well as mutants within the conserved core components of T6SSs, VgrG and DotU, were defective for all of these processes. In the case of IglE, which is a lipoprotein and localized to the outer membrane of the bacterial cell wall, residues within its N-terminus were identified to be important for IglE function. Consistent with a suggested role as a trimeric membrane puncturing device, VgrG was found to form multimers. DotU stabilized the inner membrane protein IcmF, in agreement with its function as a core T6SS component. The functionality of the secretion system was shown by the translocation of several FPI proteins into the cytosol of infected macrophages, among them IglE, IglC and VgrG, of which IglE was the most prominently secreted protein. At the same time, the secretion was dependent on the core components VgrG, DotU but also on IglG. Although we and others have shown the importance of FPI proteins for the escape of F. tularensis, it has been difficult to assess their role in the subsequent replication, since mutants that fail to escape never reach the growth-permissive cytosol. For this reason, selected FPI mutants were microinjected into the cytosol of different cell types and their growth compared to their replication upon normal uptake. Our data suggest that not only the metabolic adaptation to the cytosolic compartment is important for the replication of intracytosolic bacteria, but also the mechanism of their uptake as well as the permissiveness of the cytosolic compartment per se.

Place, publisher, year, edition, pages
Umeå: Umeå University, 2015. 82 p.
Umeå University medical dissertations, ISSN 0346-6612 ; 1708
Francisella, FPI, Type VI Secretion, Igl, DotU, VgrG, Pdp, microinjection, phagosomal escape, intracellular replication
National Category
Microbiology in the medical area
Research subject
Clinical Bacteriology
urn:nbn:se:umu:diva-101321 (URN)978-91-7601-246-8 (ISBN)
Public defence
2015-04-24, sal E04, byggnad 6E, NUS, Norrlands universitetssjukhus, Umeå, 10:00 (English)
Available from: 2015-04-01 Created: 2015-03-27 Last updated: 2015-05-08Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full textPubMed

Search in DiVA

By author/editor
Meyer, LenaSjöstedt, Anders
By organisation
Clinical BacteriologyMolecular Infection Medicine Sweden (MIMS)
In the same journal
Proceedings of the National Academy of Sciences of the United States of America
Infectious MedicineMicrobiology 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: 83 hits
ReferencesLink to record
Permanent link

Direct link