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Haggerty K, Cantlay S, Young E, Cashbaugh MK, Delatore Iii EF, Schreiber R, Hess H, Komlosi DR, Butler S, Bolon D, Evangelista T, Hager T, Kelly C, Phillips K, Voellinger J, Shanks RMQ, Horzempa J. Identification of an N-terminal tag (580N) that improves the biosynthesis of fluorescent proteins in Francisella tularensis and other Gram-negative bacteria. Mol Cell Probes 2024; 74:101956. [PMID: 38492609 PMCID: PMC11000650 DOI: 10.1016/j.mcp.2024.101956] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2023] [Revised: 03/12/2024] [Accepted: 03/13/2024] [Indexed: 03/18/2024]
Abstract
Utilization of fluorescent proteins is widespread for the study of microbial pathogenesis and host-pathogen interactions. Here, we discovered that linkage of the 36 N-terminal amino acids of FTL_0580 (a hypothetical protein of Francisella tularensis) to fluorescent proteins increases the fluorescence emission of bacteria that express these recombinant fusions. This N-terminal peptide will be referred to as 580N. Western blotting revealed that the linkage of 580N to Emerald Green Fluorescent Protein (EmGFP) in F. tularensis markedly improved detection of this protein. We therefore hypothesized that transcripts containing 580N may be translated more efficiently than those lacking the coding sequence for this leader peptide. In support, expression of emGFPFt that had been codon-optimized for F. tularensis, yielded significantly enhanced fluorescence than its non-optimized counterpart. Furthermore, fusing emGFP with coding sequence for a small N-terminal peptide (Serine-Lysine-Isoleucine-Lysine), which had previously been shown to inhibit ribosomal stalling, produced robust fluorescence when expressed in F. tularensis. These findings support the interpretation that 580N enhances the translation efficiency of fluorescent proteins in F. tularensis. Interestingly, expression of non-optimized 580N-emGFP produced greater fluorescence intensity than any other construct. Structural predictions suggested that RNA secondary structure also may be influencing translation efficiency. When expressed in Escherichia coli and Klebsiella pneumoniae bacteria, 580N-emGFP produced increased green fluorescence compared to untagged emGFP (neither allele was codon optimized for these bacteria). In conclusion, fusing the coding sequence for the 580N leader peptide to recombinant genes might serve as an economical alternative to codon optimization for enhancing protein expression in bacteria.
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Affiliation(s)
- Kristen Haggerty
- Department of Biomedical Sciences, West Liberty University, West Liberty, WV, USA
| | - Stuart Cantlay
- Department of Biomedical Sciences, West Liberty University, West Liberty, WV, USA
| | - Emily Young
- Department of Biomedical Sciences, West Liberty University, West Liberty, WV, USA
| | - Mariah K Cashbaugh
- Department of Biomedical Sciences, West Liberty University, West Liberty, WV, USA
| | - Elio F Delatore Iii
- Department of Biomedical Sciences, West Liberty University, West Liberty, WV, USA
| | - Rori Schreiber
- Department of Biomedical Sciences, West Liberty University, West Liberty, WV, USA
| | - Hayden Hess
- Department of Biomedical Sciences, West Liberty University, West Liberty, WV, USA
| | - Daniel R Komlosi
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA
| | - Sarah Butler
- Department of Biomedical Sciences, West Liberty University, West Liberty, WV, USA
| | - Dalton Bolon
- Department of Biomedical Sciences, West Liberty University, West Liberty, WV, USA
| | - Theresa Evangelista
- Department of Biomedical Sciences, West Liberty University, West Liberty, WV, USA
| | - Takoda Hager
- Department of Biomedical Sciences, West Liberty University, West Liberty, WV, USA
| | - Claire Kelly
- Department of Biomedical Sciences, West Liberty University, West Liberty, WV, USA
| | - Katherine Phillips
- Department of Biomedical Sciences, West Liberty University, West Liberty, WV, USA
| | - Jada Voellinger
- Department of Biomedical Sciences, West Liberty University, West Liberty, WV, USA
| | - Robert M Q Shanks
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA
| | - Joseph Horzempa
- Department of Biomedical Sciences, West Liberty University, West Liberty, WV, USA.
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van Hoek ML, Marchesani A, Rawat M. Diverse roles of low-molecular weight thiol GSH in Francisella's virulence, location sensing and GSH-stealing from host. CURRENT RESEARCH IN MICROBIAL SCIENCES 2023; 6:100218. [PMID: 38303966 PMCID: PMC10831187 DOI: 10.1016/j.crmicr.2023.100218] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2024] Open
Abstract
Low-molecular weight (LMW) thiols, encompassing peptides and small proteins with active cysteine residue(s), are important to bacteria as they are involved in a wide range of redox reactions. They include the tripeptide glutathione (GSH) and the small redox proteins, thioredoxins and glutaredoxins. We review the low MW thiols and related molecules in Francisella species and what role they may play in growth and virulence. Genes for GSH biosynthesis, metabolism and thioredoxins are present in all strains of Francisella, including the fully human-virulent strains. GSH and cysteine (CSH) are the major LMW thiols in Francisella extracts. We explore the potential role of the LMW thiols to overcome the nutritional challenges of intracellular growth (high GSH conditions) as well as the nutritional challenges of planktonic growth (low GSH conditions), and their contribution to Francisella's sensing its environmental location. Francisella may also use GSH as a source of CSH, for which it is auxotrophic. "Glutathione stealing" from the host may be an important part of Francisella's success strategy as a facultative intracellular pathogen both to detect its location and obtain CSH. An understanding of GSH metabolism in Francisella provides insights into the interaction of this pathogen with its host and may reveal additional targets for therapeutic intervention for tularemia infections.
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Affiliation(s)
- Monique L. van Hoek
- School of Systems Biology, George Mason University, Manassas, VA, United States
| | | | - Mamta Rawat
- Biology Department, California State University, Fresno, CA, United States
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Wang Y, Ledvina HE, Tower CA, Kambarev S, Liu E, Charity JC, Kreuk LSM, Tang Q, Chen Q, Gallagher LA, Radey MC, Rerolle GF, Li Y, Penewit KM, Turkarslan S, Skerrett SJ, Salipante SJ, Baliga NS, Woodward JJ, Dove SL, Peterson SB, Celli J, Mougous JD. Discovery of a glutathione utilization pathway in Francisella that shows functional divergence between environmental and pathogenic species. Cell Host Microbe 2023; 31:1359-1370.e7. [PMID: 37453420 PMCID: PMC10763578 DOI: 10.1016/j.chom.2023.06.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2023] [Revised: 05/19/2023] [Accepted: 06/20/2023] [Indexed: 07/18/2023]
Abstract
Glutathione (GSH) is an abundant metabolite within eukaryotic cells that can act as a signal, a nutrient source, or serve in a redox capacity for intracellular bacterial pathogens. For Francisella, GSH is thought to be a critical in vivo source of cysteine; however, the cellular pathways permitting GSH utilization by Francisella differ between strains and have remained poorly understood. Using genetic screening, we discovered a unique pathway for GSH utilization in Francisella. Whereas prior work suggested GSH catabolism initiates in the periplasm, the pathway we define consists of a major facilitator superfamily (MFS) member that transports intact GSH and a previously unrecognized bacterial cytoplasmic enzyme that catalyzes the first step of GSH degradation. Interestingly, we find that the transporter gene for this pathway is pseudogenized in pathogenic Francisella, explaining phenotypic discrepancies in GSH utilization among Francisella spp. and revealing a critical role for GSH in the environmental niche of these bacteria.
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Affiliation(s)
- Yaxi Wang
- Department of Microbiology, University of Washington, Seattle, WA 98109, USA
| | - Hannah E Ledvina
- Department of Microbiology, University of Washington, Seattle, WA 98109, USA
| | - Catherine A Tower
- Department of Microbiology, University of Washington, Seattle, WA 98109, USA
| | - Stanimir Kambarev
- Paul G. Allen School for Global Health, Washington State University, Pullman, WA 99164, USA
| | - Elizabeth Liu
- Department of Microbiology, University of Washington, Seattle, WA 98109, USA
| | - James C Charity
- Division of Infectious Diseases, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | | | - Qing Tang
- Department of Microbiology, University of Washington, Seattle, WA 98109, USA
| | - Qiwen Chen
- Department of Microbiology, University of Washington, Seattle, WA 98109, USA
| | - Larry A Gallagher
- Department of Microbiology, University of Washington, Seattle, WA 98109, USA
| | - Matthew C Radey
- Department of Microbiology, University of Washington, Seattle, WA 98109, USA
| | - Guilhem F Rerolle
- Department of Medicine, University of Washington, Seattle, WA 98195, USA
| | - Yaqiao Li
- Department of Microbiology, University of Washington, Seattle, WA 98109, USA; Institute for Systems Biology, Seattle, WA 98109, USA
| | - Kelsi M Penewit
- Department of Laboratory Medicine and Pathology, University of Washington, Seattle, WA 98195, USA
| | | | - Shawn J Skerrett
- Department of Medicine, University of Washington, Seattle, WA 98195, USA
| | - Stephen J Salipante
- Department of Laboratory Medicine and Pathology, University of Washington, Seattle, WA 98195, USA
| | | | - Joshua J Woodward
- Department of Microbiology, University of Washington, Seattle, WA 98109, USA
| | - Simon L Dove
- Division of Infectious Diseases, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - S Brook Peterson
- Department of Microbiology, University of Washington, Seattle, WA 98109, USA
| | - Jean Celli
- Paul G. Allen School for Global Health, Washington State University, Pullman, WA 99164, USA
| | - Joseph D Mougous
- Department of Microbiology, University of Washington, Seattle, WA 98109, USA; Microbial Interactions and Microbiome Center, University of Washington, Seattle, WA 98195, USA; Howard Hughes Medical Institute, University of Washington, Seattle, WA 98109, USA.
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4
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Köppen K, Fatykhova D, Holland G, Rauch J, Tappe D, Graff M, Rydzewski K, Hocke AC, Hippenstiel S, Heuner K. Ex vivo infection model for Francisella using human lung tissue. Front Cell Infect Microbiol 2023; 13:1224356. [PMID: 37492528 PMCID: PMC10365108 DOI: 10.3389/fcimb.2023.1224356] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2023] [Accepted: 06/23/2023] [Indexed: 07/27/2023] Open
Abstract
Introduction Tularemia is mainly caused by Francisella tularensis (Ft) subsp. tularensis (Ftt) and Ft subsp. holarctica (Ftt) in humans and in more than 200 animal species including rabbits and hares. Human clinical manifestations depend on the route of infection and range from flu-like symptoms to severe pneumonia with a mortality rate up to 60% without treatment. So far, only 2D cell culture and animal models are used to study Francisella virulence, but the gained results are transferable to human infections only to a certain extent. Method In this study, we firstly established an ex vivo human lung tissue infection model using different Francisella strains: Ftt Life Vaccine Strain (LVS), Ftt LVS ΔiglC, Ftt human clinical isolate A-660 and a German environmental Francisella species strain W12-1067 (F-W12). Human lung tissue was used to determine the colony forming units and to detect infected cell types by using spectral immunofluorescence and electron microscopy. Chemokine and cytokine levels were measured in culture supernatants. Results Only LVS and A-660 were able to grow within the human lung explants, whereas LVS ΔiglC and F-W12 did not replicate. Using human lung tissue, we observed a greater increase of bacterial load per explant for patient isolate A-660 compared to LVS, whereas a similar replication of both strains was observed in cell culture models with human macrophages. Alveolar macrophages were mainly infected in human lung tissue, but Ftt was also sporadically detected within white blood cells. Although Ftt replicated within lung tissue, an overall low induction of pro-inflammatory cytokines and chemokines was observed. A-660-infected lung explants secreted slightly less of IL-1β, MCP-1, IP-10 and IL-6 compared to Ftt LVS-infected explants, suggesting a more repressed immune response for patient isolate A-660. When LVS and A-660 were used for simultaneous co-infections, only the ex vivo model reflected the less virulent phenotype of LVS, as it was outcompeted by A-660. Conclusion We successfully implemented an ex vivo infection model using human lung tissue for Francisella. The model delivers considerable advantages and is able to discriminate virulent Francisella from less- or non-virulent strains and can be used to investigate the role of specific virulence factors.
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Affiliation(s)
- Kristin Köppen
- Working group “Cellular Interactions of Bacterial Pathogens”, Centre for Biological Threats and Special Pathogens, Highly Pathogenic Microorganisms (ZBS 2), Robert Koch Institute, Berlin, Germany
| | - Diana Fatykhova
- Department of Infectious Diseases, Respiratory Medicine and Critical Care, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
| | - Gudrun Holland
- Advanced Light and Electron Microscopy, ZBS 4, Robert Koch Institute, Berlin, Germany
| | - Jessica Rauch
- Research Group Zoonoses, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany
| | - Dennis Tappe
- Research Group Zoonoses, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany
| | - Mareike Graff
- Department for General and Thoracic Surgery, DRK Clinics, Berlin, Germany
| | - Kerstin Rydzewski
- Working group “Cellular Interactions of Bacterial Pathogens”, Centre for Biological Threats and Special Pathogens, Highly Pathogenic Microorganisms (ZBS 2), Robert Koch Institute, Berlin, Germany
| | - Andreas C. Hocke
- Department of Infectious Diseases, Respiratory Medicine and Critical Care, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
| | - Stefan Hippenstiel
- Department of Infectious Diseases, Respiratory Medicine and Critical Care, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
| | - Klaus Heuner
- Working group “Cellular Interactions of Bacterial Pathogens”, Centre for Biological Threats and Special Pathogens, Highly Pathogenic Microorganisms (ZBS 2), Robert Koch Institute, Berlin, Germany
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Nakamura T, Shimizu T, Ikegaya R, Uda A, Watanabe K, Watarai M. Identification of pyrC gene as an immunosuppressive factor in Francisella novicida infection. Front Cell Infect Microbiol 2022; 12:1027424. [DOI: 10.3389/fcimb.2022.1027424] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2022] [Accepted: 10/13/2022] [Indexed: 11/13/2022] Open
Abstract
Francisella tularensis, a bacterial causative agent of the zoonosis tularemia, is highly pathogenic to humans. The pathogenicity of this bacterium is characterized by intracellular growth in immune cells, like macrophages, and host immune suppression. However, the detailed mechanism of immune suppression by F. tularensis is still unclear. To identify the key factors causing Francisella-mediated immunosuppression, large-scale screening using a transposon random mutant library containing 3552 mutant strains of F. tularensis subsp. novicida (F. novicida) was performed. Thirteen mutants that caused stronger tumor necrosis factor (TNF)-α production in infected U937 human macrophage cells than the wild-type F. novicida strain were isolated. Sequencing analysis of transposon insertion sites revealed 10 genes, including six novel genes, as immunosuppressive factors of Francisella. Among these, the relationship of the pyrC gene, which encodes dihydroorotase in the pyrimidine biosynthesis pathway, with Francisella-mediated immunosuppression was investigated. The pyrC deletion mutant strain (ΔpyrC) induced higher TNF-α production in U937 host cells than the wild-type F. novicida strain. The ΔpyrC mutant strain was also found to enhance host interleukin-1β and interferon (IFN)-β production. The heat-inactivated ΔpyrC mutant strain could not induce host TNF-α production. Moreover, the production of IFN-β resulting from ΔpyrC infection in U937 cells was repressed upon treatment with the stimulator of interferon genes (STING)-specific inhibitor, H-151. These results suggest that pyrC is related to the immunosuppressive activity and pathogenicity of Francisella via the STING pathway.
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Cantlay S, Kaftanic C, Horzempa J. PdpC, a secreted effector protein of the type six secretion system, is required for erythrocyte invasion by Francisella tularensis LVS. Front Cell Infect Microbiol 2022; 12:979693. [PMID: 36237421 PMCID: PMC9552824 DOI: 10.3389/fcimb.2022.979693] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2022] [Accepted: 09/02/2022] [Indexed: 12/01/2022] Open
Abstract
Francisella tularensis is a gram negative, intracellular pathogen that is the causative agent of the potentially fatal disease, tularemia. During infection, F. tularensis is engulfed by and replicates within host macrophages. Additionally, this bacterium has also been shown to invade human erythrocytes and, in both cases, the Type Six Secretion System (T6SS) is required for these host-pathogen interaction. One T6SS effector protein, PdpC, is important for macrophage infection, playing a role in phagolysosomal escape and intracellular replication. To determine if PdpC also plays a role in erythrocyte invasion, we constructed a pdpC-null mutant in the live vaccine strain, F. tularensis LVS. We show that PdpC is required for invasion of human and sheep erythrocytes during in vitro assays and that reintroduction of a copy of pdpC, in trans, rescues this phenotype. The interaction with human erythrocytes was further characterized using double-immunofluorescence microscopy to show that PdpC is required for attachment of F. tularensis LVS to erythrocytes as well as invasion. To learn more about the role of PdpC in erythrocyte invasion we generated a strain of F. tularensis LVS expressing pdpC-emgfp. PdpC-EmGFP localizes as discrete foci in a subset of F. tularensis LVS cells grown in broth culture and accumulates in erythrocytes during invasion assays. Our results are the first example of a secreted effector protein of the T6SS shown to be involved in erythrocyte invasion and indicate that PdpC is secreted into erythrocytes during invasion.
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Affiliation(s)
| | | | - Joseph Horzempa
- Department of Biological Sciences, West Liberty University, West Liberty, WV, United States
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Ozanic M, Marecic V, Knezevic M, Kelava I, Stojková P, Lindgren L, Bröms JE, Sjöstedt A, Abu Kwaik Y, Santic M. The type IV pili component PilO is a virulence determinant of Francisella novicida. PLoS One 2022; 17:e0261938. [PMID: 35077486 PMCID: PMC8789160 DOI: 10.1371/journal.pone.0261938] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2021] [Accepted: 12/14/2021] [Indexed: 12/03/2022] Open
Abstract
Francisella tularensis is a highly pathogenic intracellular bacterium that causes the disease tularemia. While its ability to replicate within cells has been studied in much detail, the bacterium also encodes a less characterised type 4 pili (T4P) system. T4Ps are dynamic adhesive organelles identified as major virulence determinants in many human pathogens. In F. tularensis, the T4P is required for adherence to the host cell, as well as for protein secretion. Several components, including pilins, a pili peptidase, a secretin pore and two ATPases, are required to assemble a functional T4P, and these are encoded within distinct clusters on the Francisella chromosome. While some of these components have been functionally characterised, the role of PilO, if any, still is unknown. Here, we examined the role of PilO in the pathogenesis of F. novicida. Our results show that the PilO is essential for pilus assembly on the bacterial surface. In addition, PilO is important for adherence of F. novicida to human monocyte-derived macrophages, secretion of effector proteins and intracellular replication. Importantly, the pilO mutant is attenuated for virulence in BALB/c mice regardless of the route of infection. Following intratracheal and intradermal infection, the mutant caused no histopathology changes, and demonstrated impaired phagosomal escape and replication within lung liver as well as spleen. Thus, PilO is an essential virulence determinant of F. novicida.
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Affiliation(s)
- Mateja Ozanic
- Faculty of Medicine, Department of Microbiology and Parasitology, University of Rijeka, Rijeka, Croatia
| | - Valentina Marecic
- Faculty of Medicine, Department of Microbiology and Parasitology, University of Rijeka, Rijeka, Croatia
| | - Masa Knezevic
- Faculty of Medicine, Department of Microbiology and Parasitology, University of Rijeka, Rijeka, Croatia
| | - Ina Kelava
- Faculty of Medicine, Department of Microbiology and Parasitology, University of Rijeka, Rijeka, Croatia
| | - Pavla Stojková
- Department of Clinical Microbiology and Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University, Umeå, Sweden
| | - Lena Lindgren
- Department of Clinical Microbiology and Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University, Umeå, Sweden
| | - Jeanette E. Bröms
- Department of Clinical Microbiology and Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University, Umeå, Sweden
| | - Anders Sjöstedt
- Department of Clinical Microbiology and Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University, Umeå, Sweden
| | - Yousef Abu Kwaik
- Department of Microbiology and Immunology and Center for Predictive Medicine, College of Medicine, University of Louisville, Louisville, Kentucky, United States of America
| | - Marina Santic
- Faculty of Medicine, Department of Microbiology and Parasitology, University of Rijeka, Rijeka, Croatia
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Deletion Mutants of Francisella Phagosomal Transporters FptA and FptF Are Highly Attenuated for Virulence and Are Protective Against Lethal Intranasal Francisella LVS Challenge in a Murine Model of Respiratory Tularemia. Pathogens 2021; 10:pathogens10070799. [PMID: 34202420 PMCID: PMC8308642 DOI: 10.3390/pathogens10070799] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2021] [Revised: 06/09/2021] [Accepted: 06/17/2021] [Indexed: 11/17/2022] Open
Abstract
Francisella tularensis (Ft) is a Gram-negative, facultative intracellular bacterium that is a Tier 1 Select Agent of concern for biodefense for which there is no licensed vaccine. A subfamily of 9 Francisella phagosomal transporter (fpt) genes belonging to the Major Facilitator Superfamily of transporters was identified as critical to pathogenesis and potential targets for attenuation and vaccine development. We evaluated the attenuation and protective capacity of LVS derivatives with deletions of the fptA and fptF genes in the C57BL/6J mouse model of respiratory tularemia. LVSΔfptA and LVSΔfptF were highly attenuated with LD50 values of >20 times that of LVS when administered intranasally and conferred 100% protection against lethal challenge. Immune responses to the fpt mutant strains in mouse lungs on day 6 post-infection were substantially modified compared to LVS and were associated with reduced organ burdens and reduced pathology. The immune responses to LVSΔfptA and LVSΔfptF were characterized by decreased levels of IL-10 and IL-1β in the BALF versus LVS, and increased numbers of B cells, αβ and γδ T cells, NK cells, and DCs versus LVS. These results support a fundamental requirement for FptA and FptF in the pathogenesis of Ft and the modulation of the host immune response.
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Cunningham AL, Mann BJ, Qin A, Santiago AE, Grassel C, Lipsky M, Vogel SN, Barry EM. Characterization of Schu S4 aro mutants as live attenuated tularemia vaccine candidates. Virulence 2021; 11:283-294. [PMID: 32241221 PMCID: PMC7161688 DOI: 10.1080/21505594.2020.1746557] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
There is a need for development of an effective vaccine against Francisella tularensis, as this potential bioweapon has a high mortality rate and low infectious dose when delivered via the aerosol route. Moreover, this Tier 1 agent has a history of weaponization. We engineered targeted mutations in the Type A strain F. tularensis subspecies tularensis Schu S4 in aro genes encoding critical enzymes in aromatic amino acid biosynthesis. F. tularensis Schu S4ΔaroC, Schu S4ΔaroD, and Schu S4ΔaroCΔaroD mutant strains were attenuated for intracellular growth in vitro and for virulence in vivo and, conferred protection against pulmonary wild-type (WT) F. tularensis Schu S4 challenge in the C57BL/6 mouse model. F. tularensis Schu S4ΔaroD was identified as the most promising vaccine candidate, demonstrating protection against high-dose intranasal challenge; it protected against 1,000 CFU Schu S4, the highest level of protection tested to date. It also provided complete protection against challenge with 92 CFU of a F. tularensis subspecies holarctica strain (Type B). Mice responded to vaccination with Schu S4ΔaroD with systemic IgM and IgG2c, as well as the production of a functional T cell response as measured in the splenocyte-macrophage co-culture assay. This vaccine was further characterized for dissemination, histopathology, and cytokine/chemokine gene induction at defined time points following intranasal vaccination which confirmed its attenuation compared to WT Schu S4. Cytokine, chemokine, and antibody induction patterns compared to wild-type Schu S4 distinguish protective vs. pathogenic responses to F. tularensis and elucidate correlates of protection associated with vaccination against this agent.
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Affiliation(s)
| | - Barbara J Mann
- Department of Medicine, Division of Infectious Diseases and International Heath, University of Virginia, Charlottesville, VA, USA
| | - Aiping Qin
- Department of Medicine, Division of Infectious Diseases and International Heath, University of Virginia, Charlottesville, VA, USA
| | - Araceli E Santiago
- Department of Pediatrics, University of Virginia, Charlottesville, VA, USA
| | - Christen Grassel
- Center for Vaccine Development, University of Maryland Baltimore, Baltimore, MD, USA
| | - Michael Lipsky
- Department of Pathology, University of Maryland Baltimore, Baltimore, MD, USA
| | - Stefanie N Vogel
- Department of Microbiology and Immunology, University of Maryland Baltimore, Baltimore, MD, USA
| | - Eileen M Barry
- Center for Vaccine Development, University of Maryland Baltimore, Baltimore, MD, USA
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10
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Using proteomics to identify host cell interaction partners for VgrG and IglJ. Sci Rep 2020; 10:14612. [PMID: 32884055 PMCID: PMC7471685 DOI: 10.1038/s41598-020-71641-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2020] [Accepted: 07/23/2020] [Indexed: 11/17/2022] Open
Abstract
Francisella tularensis is a highly virulent intracellular bacterium and the causative agent of tularemia. The disease is characterized by the suboptimal innate immune response and consequently by the impaired adaptive immunity. The virulence of this pathogen depends on proteins encoded by a genomic island termed the Francisella Pathogenicity Island (FPI). However, the precise biological roles of most of the FPI-encoded proteins remain to be clarified. In this study, we employed stable isotope labeling by amino acids in cell culture (SILAC) in combination with affinity protein purification coupled with liquid chromatography–mass spectrometry to identify potential protein-effector binding pairs for two FPI virulence effectors IglJ and VgrG. Our results may indicate that while the IglJ protein interactions primarily affect mitochondria, the VgrG interactions affect phagosome and/or autophagosome biogenesis via targeting components of the host’s exocyst complex.
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11
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OpiA, a Type Six Secretion System Substrate, Localizes to the Cell Pole and Plays a Role in Bacterial Growth and Viability in Francisella tularensis LVS. J Bacteriol 2020; 202:JB.00048-20. [PMID: 32366588 DOI: 10.1128/jb.00048-20] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Accepted: 04/26/2020] [Indexed: 12/19/2022] Open
Abstract
Francisella tularensis is an intracellular pathogen and the causative agent of tularemia. The F. tularensis type six secretion system (T6SS) is required for a number of host-pathogen interactions, including phagolysosomal escape and invasion of erythrocytes. One known effector of the T6SS, OpiA, has recently been shown to be a phosphatidylinositol-3 kinase. To investigate the role of OpiA in erythrocyte invasion, we constructed an opiA-null mutant in the live vaccine strain, F. tularensis LVS. OpiA was not required for erythrocyte invasion; however, deletion of opiA affected growth of F. tularensis LVS in broth cultures in a medium-dependent manner. We also found that opiA influenced cell size, gentamicin sensitivity, bacterial viability, and the lipid content of F. tularensis A fluorescently tagged OpiA (OpiA-emerald-green fluorescent protein [EmGFP]) accumulated at the cell poles of F. tularensis, which is consistent with the location of the T6SS. However, OpiA-EmGFP also exhibited a highly dynamic localization, and this fusion protein was detected in erythrocytes and THP-1 cells in vitro, further supporting that OpiA is secreted. Similar to previous reports with F. novicida, our data demonstrated that opiA had a minimal effect on intracellular replication of F. tularensis in host immune cells in vitro However, THP-1 cells infected with the opiA mutant produced modestly (but significantly) higher levels of the proinflammatory cytokine tumor necrosis factor alpha compared to these host cells infected with wild-type bacteria. We conclude that, in addition to its role in host-pathogen interactions, our results reveal that the function of opiA is central to the biology of F. tularensis bacteria.IMPORTANCE F. tularensis is a pathogenic intracellular pathogen that is of importance for public health and strategic defense. This study characterizes the opiA gene of F. tularensis LVS, an attenuated strain that has been used as a live vaccine but that also shares significant genetic similarity to related Francisella strains that cause human disease. The data presented here provide the first evidence of a T6SS effector protein that affects the physiology of F. tularensis, namely, the growth, cell size, viability, and aminoglycoside resistance of F. tularensis LVS. This study also adds insight into our understanding of OpiA as a determinant of virulence. Finally, the fluorescence fusion constructs presented here will be useful tools for dissecting the role of OpiA in infection.
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Ramsey KM, Ledvina HE, Tresko TM, Wandzilak JM, Tower CA, Tallo T, Schramm CE, Peterson SB, Skerrett SJ, Mougous JD, Dove SL. Tn-Seq reveals hidden complexity in the utilization of host-derived glutathione in Francisella tularensis. PLoS Pathog 2020; 16:e1008566. [PMID: 32492066 PMCID: PMC7340319 DOI: 10.1371/journal.ppat.1008566] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2020] [Revised: 07/07/2020] [Accepted: 04/20/2020] [Indexed: 12/27/2022] Open
Abstract
Host-derived glutathione (GSH) is an essential source of cysteine for the intracellular pathogen Francisella tularensis. In a comprehensive transposon insertion sequencing screen, we identified several F. tularensis genes that play central and previously unappreciated roles in the utilization of GSH during the growth of the bacterium in macrophages. We show that one of these, a gene we named dptA, encodes a proton-dependent oligopeptide transporter that enables growth of the organism on the dipeptide Cys-Gly, a key breakdown product of GSH generated by the enzyme γ-glutamyltranspeptidase (GGT). Although GGT was thought to be the principal enzyme involved in GSH breakdown in F. tularensis, our screen identified a second enzyme, referred to as ChaC, that is also involved in the utilization of exogenous GSH. However, unlike GGT and DptA, we show that the importance of ChaC in supporting intramacrophage growth extends beyond cysteine acquisition. Taken together, our findings provide a compendium of F. tularensis genes required for intracellular growth and identify new players in the metabolism of GSH that could be attractive targets for therapeutic intervention.
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Affiliation(s)
- Kathryn M. Ramsey
- Division of Infectious Diseases, Boston Children’s Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
- Departments of Cell and Molecular Biology and Biomedical and Pharmaceutical Sciences, University of Rhode Island, Kingston, Rhode Island, United States of America
| | - Hannah E. Ledvina
- Department of Microbiology, University of Washington School of Medicine, Seattle, Washington, United States of America
| | - Tenayaann M. Tresko
- Department of Microbiology, University of Washington School of Medicine, Seattle, Washington, United States of America
| | - Jamie M. Wandzilak
- Departments of Cell and Molecular Biology and Biomedical and Pharmaceutical Sciences, University of Rhode Island, Kingston, Rhode Island, United States of America
| | - Catherine A. Tower
- Department of Microbiology, University of Washington School of Medicine, Seattle, Washington, United States of America
| | - Thomas Tallo
- Division of Infectious Diseases, Boston Children’s Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Caroline E. Schramm
- Division of Pulmonary, Critical Care and Sleep Medicine, Harborview Medical Center, University of Washington, Seattle, Washington, United States of America
| | - S. Brook Peterson
- Department of Microbiology, University of Washington School of Medicine, Seattle, Washington, United States of America
| | - Shawn J. Skerrett
- Division of Pulmonary, Critical Care and Sleep Medicine, Harborview Medical Center, University of Washington, Seattle, Washington, United States of America
| | - Joseph D. Mougous
- Department of Microbiology, University of Washington School of Medicine, Seattle, Washington, United States of America
- Howard Hughes Medical Institute, University of Washington, Seattle, Washington, United States of America
| | - Simon L. Dove
- Division of Infectious Diseases, Boston Children’s Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
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Contributions of TolC Orthologs to Francisella tularensis Schu S4 Multidrug Resistance, Modulation of Host Cell Responses, and Virulence. Infect Immun 2019; 87:IAI.00823-18. [PMID: 30670554 DOI: 10.1128/iai.00823-18] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2018] [Accepted: 01/14/2019] [Indexed: 02/06/2023] Open
Abstract
Francisella tularensis is a Gram-negative, facultative intracellular pathogen and the causative agent of tularemia. Previous studies with the attenuated live vaccine strain (LVS) identified a role for the outer membrane protein TolC in modulation of host cell responses during infection and virulence in the mouse model of tularemia. TolC is an integral part of efflux pumps that export small molecules and type I secretion systems that export a range of bacterial virulence factors. In this study, we analyzed TolC and its two orthologs, FtlC and SilC, present in the fully virulent F. tularensis Schu S4 strain for their contributions to multidrug efflux, suppression of innate immune responses, and virulence. We found that each TolC ortholog participated in multidrug efflux, with overlapping substrate specificities for TolC and FtlC and a distinct substrate profile for SilC. In contrast to their shared roles in drug efflux, only TolC functioned in the modulation of macrophage apoptotic and proinflammatory responses to Schu S4 infection, consistent with a role in virulence factor delivery to host cells. In agreement with previous results with the LVS, the Schu S4 ΔtolC mutant was highly attenuated for virulence in mice by both the intranasal and intradermal routes of infection. Unexpectedly, FtlC was also critical for Schu S4 virulence, but only by the intradermal route. Our data demonstrate a conserved and critical role for TolC in modulation of host immune responses and Francisella virulence and also highlight strain- and route-dependent differences in the pathogenesis of tularemia.
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Cui G, Wang J, Qi X, Su J. Transcription Elongation Factor GreA Plays a Key Role in Cellular Invasion and Virulence of Francisella tularensis subsp. novicida. Sci Rep 2018; 8:6895. [PMID: 29720697 PMCID: PMC5932009 DOI: 10.1038/s41598-018-25271-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2018] [Accepted: 04/18/2018] [Indexed: 01/24/2023] Open
Abstract
Francisella tularensis is a facultative intracellular Gram-negative bacterium that causes the zoonotic disease tularemia. We identified the transcription elongation factor GreA as a virulence factor in our previous study, but its role was not defined. Here, we investigate the effects of the inactivation of the greA gene, generating a greA mutant of F. tularensis subsp. novicida. Inactivation of greA impaired the bacterial invasion into and growth within host cells, and subsequently virulence in mouse infection model. A transcriptomic analysis (RNA-Seq) showed that the loss of GreA caused the differential expression of 196 bacterial genes, 77 of which were identified as virulence factors in previous studies. To confirm that GreA regulates the expression of virulence factors involved in cell invasion by Francisella, FTN_1186 (pepO) and FTN_1551 (ampD) gene mutants were generated. The ampD deletion mutant showed reduced invasiveness into host cells. These results strongly suggest that GreA plays an important role in the pathogenesis of Francisella by affecting the expression of virulence genes and provide new insights into the complex regulation of Francisella infection.
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Affiliation(s)
- Guolin Cui
- Key Laboratory of Animal Epidemiology and Zoonosis, Ministry of Agriculture, College of Veterinary Medicine, China Agricultural University, Beijing, 100193, China
| | - Jun Wang
- Key Laboratory of Animal Epidemiology and Zoonosis, Ministry of Agriculture, College of Veterinary Medicine, China Agricultural University, Beijing, 100193, China
| | - Xinyi Qi
- Key Laboratory of Animal Epidemiology and Zoonosis, Ministry of Agriculture, College of Veterinary Medicine, China Agricultural University, Beijing, 100193, China
| | - Jingliang Su
- Key Laboratory of Animal Epidemiology and Zoonosis, Ministry of Agriculture, College of Veterinary Medicine, China Agricultural University, Beijing, 100193, China.
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Díaz FE, Abarca K, Kalergis AM. An Update on Host-Pathogen Interplay and Modulation of Immune Responses during Orientia tsutsugamushi Infection. Clin Microbiol Rev 2018; 31:e00076-17. [PMID: 29386235 PMCID: PMC5967693 DOI: 10.1128/cmr.00076-17] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The obligate intracellular bacterium Orientia tsutsugamushi is the causative agent of scrub typhus in humans, a serious mite-borne disease present in a widespread area of endemicity, which affects an estimated 1 million people every year. This disease may exhibit a broad range of presentations, ranging from asymptomatic to fatal conditions, with the latter being due to disseminated endothelial infection and organ injury. Unique characteristics of the biology and host-pathogen interactions of O. tsutsugamushi, including the high antigenic diversity among strains and the highly variable, short-lived memory responses developed by the host, underlie difficulties faced in the pursuit of an effective vaccine, which is an imperative need. Other factors that have hindered scientific progress relative to the infectious mechanisms of and the immune response triggered by this bacterium in vertebrate hosts include the limited number of mechanistic studies performed on animal models and the lack of genetic tools currently available for this pathogen. However, recent advances in animal model development are promising to improve our understanding of host-pathogen interactions. Here, we comprehensively discuss the recent advances in and future perspectives on host-pathogen interactions and the modulation of immune responses related to this reemerging disease, highlighting the role of animal models.
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Affiliation(s)
- Fabián E Díaz
- Millennium Institute on Immunology and Immunotherapy, Departamento de Genética Molecular y Microbiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Katia Abarca
- Departamento en Enfermedades Infecciosas e Inmunología Pediátricas, Facultad de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Alexis M Kalergis
- Millennium Institute on Immunology and Immunotherapy, Departamento de Genética Molecular y Microbiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile
- Departamento de Endocrinología, Facultad de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile
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Sampath V, McCaig WD, Thanassi DG. Amino acid deprivation and central carbon metabolism regulate the production of outer membrane vesicles and tubes by Francisella. Mol Microbiol 2018; 107:523-541. [PMID: 29240272 DOI: 10.1111/mmi.13897] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2017] [Revised: 12/07/2017] [Accepted: 12/11/2017] [Indexed: 12/23/2022]
Abstract
Francisella tularensis is a highly virulent Gram-negative bacterial pathogen that causes the zoonotic disease tularemia. F. novicida, a model tularemia strain, produces spherical outer membrane vesicles (OMV), as well as novel tubular vesicles and extensions of the cell surface. These OMV and tubes (OMV/T) are produced in a regulated manner and contain known virulence factors. Mechanisms by which bacterial vesicles are produced and regulated are not well understood. We performed a genetic screen in F. novicida to decipher the molecular basis for regulated OMV/T formation, and identified both hypo- and hyper-vesiculating mutants. Mutations in fumA and tktA, involved in central carbon metabolism, and in FTN_0908 and FTN_1037, of unknown function, resulted in severe defects in OMV/T production. Cysteine deprivation was identified as the signal that triggers OMV/T formation in F. novicida during growth in rich medium. We also found that fully virulent F. tularensis produces OMV/T in a similarly regulated manner. Further analysis revealed that OMV/T production is responsive to deprivation of essential amino acids in addition to cysteine, and that the hypo-vesiculating mutants are defective in responding to this signal. Thus, amino acid starvation, such as encountered by Francisella during host cell invasion, regulates the production of membrane-derived structures.
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Affiliation(s)
- Vinaya Sampath
- Department of Molecular Genetics and Microbiology, Center for Infectious Diseases, Stony Brook University, Stony Brook, NY 11794, USA
| | - William D McCaig
- Department of Molecular Genetics and Microbiology, Center for Infectious Diseases, Stony Brook University, Stony Brook, NY 11794, USA
| | - David G Thanassi
- Department of Molecular Genetics and Microbiology, Center for Infectious Diseases, Stony Brook University, Stony Brook, NY 11794, USA
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17
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Marecic V, Shevchuk O, Ozanic M, Mihelcic M, Steinert M, Jurak Begonja A, Abu Kwaik Y, Santic M. Isolation of F. novicida-Containing Phagosome from Infected Human Monocyte Derived Macrophages. Front Cell Infect Microbiol 2017; 7:303. [PMID: 28725638 PMCID: PMC5496951 DOI: 10.3389/fcimb.2017.00303] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2017] [Accepted: 06/20/2017] [Indexed: 11/28/2022] Open
Abstract
Francisella is a gram-negative bacterial pathogen, which causes tularemia in humans and animals. A crucial step of Francisella infection is its invasion of macrophage cells. Biogenesis of the Francisella-containing phagosome (FCP) is arrested for ~15 min at the endosomal stage, followed by gradual bacterial escape into the cytosol, where the microbe proliferates. The crucial step in pathogenesis of tularemia is short and transient presence of the bacterium within phagosome. Isolation of FCPs for further studies has been challenging due to the short period of time of bacterial residence in it and the characteristics of the FCP. Here, we will for the first time present the method for isolation of the FCPs from infected human monocytes-derived macrophages (hMDMs). For elimination of lysosomal compartment these organelles were pre-loaded with dextran coated colloidal iron particles prior infection and eliminated by magnetic separation of the post-nuclear supernatant (PNS). We encountered the challenge that mitochondria has similar density to the FCP. To separate the FCP in the PNS from mitochondria, we utilized iodophenylnitrophenyltetrazolium, which is converted by the mitochondrial succinate dehydrogenase into formazan, leading to increased density of the mitochondria and allowing separation by the discontinuous sucrose density gradient ultracentrifugation. The purity of the FCP preparation and its acquisition of early endosomal markers was confirmed by Western blots, confocal and transmission electron microscopy. Our strategy to isolate highly pure FCPs from macrophages should facilitate studies on the FCP and its biogenesis.
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Affiliation(s)
- Valentina Marecic
- Department of Microbiology and Parasitology, Faculty of Medicine, University of RijekaRijeka, Croatia
| | - Olga Shevchuk
- Department of Microbiology, Institut für Mikrobiologie, Technische Universität Braunschweig and Helmholtz Center for Infection ResearchBraunschweig, Germany.,Department of Biotechnology, University of RijekaRijeka, Croatia
| | - Mateja Ozanic
- Department of Microbiology and Parasitology, Faculty of Medicine, University of RijekaRijeka, Croatia
| | - Mirna Mihelcic
- Department of Microbiology and Parasitology, Faculty of Medicine, University of RijekaRijeka, Croatia
| | - Michael Steinert
- Department of Microbiology, Institut für Mikrobiologie, Technische Universität Braunschweig and Helmholtz Center for Infection ResearchBraunschweig, Germany
| | | | - Yousef Abu Kwaik
- Department of Microbiology and Immunology and Center for Predictive MedicineLouisville, KY, United States
| | - Marina Santic
- Department of Microbiology and Parasitology, Faculty of Medicine, University of RijekaRijeka, Croatia
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Schmitt DM, Barnes R, Rogerson T, Haught A, Mazzella LK, Ford M, Gilson T, Birch JWM, Sjöstedt A, Reed DS, Franks JM, Stolz DB, Denvir J, Fan J, Rekulapally S, Primerano DA, Horzempa J. The Role and Mechanism of Erythrocyte Invasion by Francisella tularensis. Front Cell Infect Microbiol 2017; 7:173. [PMID: 28536678 PMCID: PMC5423315 DOI: 10.3389/fcimb.2017.00173] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2017] [Accepted: 04/21/2017] [Indexed: 01/06/2023] Open
Abstract
Francisella tularensis is an extremely virulent bacterium that can be transmitted naturally by blood sucking arthropods. During mammalian infection, F. tularensis infects numerous types of host cells, including erythrocytes. As erythrocytes do not undergo phagocytosis or endocytosis, it remains unknown how F. tularensis invades these cells. Furthermore, the consequence of inhabiting the intracellular space of red blood cells (RBCs) has not been determined. Here, we provide evidence indicating that residing within an erythrocyte enhances the ability of F. tularensis to colonize ticks following a blood meal. Erythrocyte residence protected F. tularensis from a low pH environment similar to that of gut cells of a feeding tick. Mechanistic studies revealed that the F. tularensis type VI secretion system (T6SS) was required for erythrocyte invasion as mutation of mglA (a transcriptional regulator of T6SS genes), dotU, or iglC (two genes encoding T6SS machinery) severely diminished bacterial entry into RBCs. Invasion was also inhibited upon treatment of erythrocytes with venom from the Blue-bellied black snake (Pseudechis guttatus), which aggregates spectrin in the cytoskeleton, but not inhibitors of actin polymerization and depolymerization. These data suggest that erythrocyte invasion by F. tularensis is dependent on spectrin utilization which is likely mediated by effectors delivered through the T6SS. Our results begin to elucidate the mechanism of a unique biological process facilitated by F. tularensis to invade erythrocytes, allowing for enhanced colonization of ticks.
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Affiliation(s)
- Deanna M Schmitt
- Department of Natural Sciences and Mathematics, West Liberty UniversityWest Liberty, WV, USA
| | - Rebecca Barnes
- Department of Natural Sciences and Mathematics, West Liberty UniversityWest Liberty, WV, USA
| | - Taylor Rogerson
- Department of Natural Sciences and Mathematics, West Liberty UniversityWest Liberty, WV, USA
| | - Ashley Haught
- Department of Natural Sciences and Mathematics, West Liberty UniversityWest Liberty, WV, USA
| | - Leanne K Mazzella
- Department of Natural Sciences and Mathematics, West Liberty UniversityWest Liberty, WV, USA
| | - Matthew Ford
- Department of Natural Sciences and Mathematics, West Liberty UniversityWest Liberty, WV, USA
| | - Tricia Gilson
- Department of Natural Sciences and Mathematics, West Liberty UniversityWest Liberty, WV, USA
| | - James W-M Birch
- Department of Natural Sciences and Mathematics, West Liberty UniversityWest Liberty, WV, USA
| | - Anders Sjöstedt
- Department of Clinical Microbiology, Clinical Bacteriology, and Laboratory for Molecular Infection Medicine Sweden, Umeå UniversityUmeå, Sweden
| | - Douglas S Reed
- Regional Biocontainment Laboratory, Center for Vaccine Research, University of PittsburghPittsburgh, PA, USA
| | - Jonathan M Franks
- Center for Biologic Imaging, University of Pittsburgh School of MedicinePittsburgh, PA, USA
| | - Donna B Stolz
- Center for Biologic Imaging, University of Pittsburgh School of MedicinePittsburgh, PA, USA
| | - James Denvir
- Department of Biomedical Sciences, Joan C. Edwards School of Medicine, Marshall UniversityHuntington, WV, USA
| | - Jun Fan
- Department of Biomedical Sciences, Joan C. Edwards School of Medicine, Marshall UniversityHuntington, WV, USA
| | - Swanthana Rekulapally
- Department of Biomedical Sciences, Joan C. Edwards School of Medicine, Marshall UniversityHuntington, WV, USA
| | - Donald A Primerano
- Department of Biomedical Sciences, Joan C. Edwards School of Medicine, Marshall UniversityHuntington, WV, USA
| | - Joseph Horzempa
- Department of Natural Sciences and Mathematics, West Liberty UniversityWest Liberty, WV, USA
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Ziveri J, Barel M, Charbit A. Importance of Metabolic Adaptations in Francisella Pathogenesis. Front Cell Infect Microbiol 2017; 7:96. [PMID: 28401066 PMCID: PMC5368251 DOI: 10.3389/fcimb.2017.00096] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2017] [Accepted: 03/13/2017] [Indexed: 01/25/2023] Open
Abstract
Francisella tularensis is a highly infectious Gram-negative bacterium and the causative agent of the zoonotic disease tularemia. This bacterial pathogen can infect a broad variety of animal species and can be transmitted to humans in numerous ways with various clinical outcomes. Although, Francisella possesses the capacity to infect numerous mammalian cell types, the macrophage constitutes the main intracellular niche, used for in vivo bacterial dissemination. To survive and multiply within infected macrophages, Francisella must imperatively escape from the phagosomal compartment. In the cytosol, the bacterium needs to control the host innate immune response and adapt its metabolism to this nutrient-restricted niche. Our laboratory has shown that intracellular Francisella mainly relied on host amino acid as major gluconeogenic substrates and provided evidence that the host metabolism was also modified upon Francisella infection. We will review here our current understanding of how Francisella copes with the available nutrient sources provided by the host cell during the course of infection.
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Affiliation(s)
- Jason Ziveri
- Sorbonne Paris Cité, Université Paris DescartesParis, France; Institut National de la Santé et de la Recherche Médicale U1151 - Centre National de la Recherche Scientifique UMR 8253, Institut Necker-Enfants Malades, Team 11: Pathogenesis of Systemic InfectionsParis, France
| | - Monique Barel
- Sorbonne Paris Cité, Université Paris DescartesParis, France; Institut National de la Santé et de la Recherche Médicale U1151 - Centre National de la Recherche Scientifique UMR 8253, Institut Necker-Enfants Malades, Team 11: Pathogenesis of Systemic InfectionsParis, France
| | - Alain Charbit
- Sorbonne Paris Cité, Université Paris DescartesParis, France; Institut National de la Santé et de la Recherche Médicale U1151 - Centre National de la Recherche Scientifique UMR 8253, Institut Necker-Enfants Malades, Team 11: Pathogenesis of Systemic InfectionsParis, France
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20
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Sarva ST, Waldo RH, Belland RJ, Klose KE. Comparative Transcriptional Analyses of Francisella tularensis and Francisella novicida. PLoS One 2016; 11:e0158631. [PMID: 27537327 PMCID: PMC4990168 DOI: 10.1371/journal.pone.0158631] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2016] [Accepted: 06/20/2016] [Indexed: 01/18/2023] Open
Abstract
Francisella tularensis is composed of a number of subspecies with varied geographic distribution, host ranges, and virulence. In view of these marked differences, comparative functional genomics may elucidate some of the molecular mechanism(s) behind these differences. In this study a shared probe microarray was designed that could be used to compare the transcriptomes of Francisella tularensis subsp. tularensis Schu S4 (Ftt), Francisella tularensis subsp. holarctica OR960246 (Fth), Francisella tularensis subsp. holarctica LVS (LVS), and Francisella novicida U112 (Fn). To gain insight into expression differences that may be related to the differences in virulence of these subspecies, transcriptomes were measured from each strain grown in vitro under identical conditions, utilizing a shared probe microarray. The human avirulent Fn strain exhibited high levels of transcription of genes involved in general metabolism, which are pseudogenes in the human virulent Ftt and Fth strains, consistent with the process of genome decay in the virulent strains. Genes encoding an efflux system (emrA2 cluster of genes), siderophore (fsl operon), acid phosphatase, LPS synthesis, polyamine synthesis, and citrulline ureidase were all highly expressed in Ftt when compared to Fn, suggesting that some of these may contribute to the relative high virulence of Ftt. Genes expressed at a higher level in Ftt when compared to the relatively less virulent Fth included genes encoding isochorismatases, cholylglycine hydrolase, polyamine synthesis, citrulline ureidase, Type IV pilus subunit, and the Francisella Pathogenicity Island protein PdpD. Fth and LVS had very few expression differences, consistent with the derivation of LVS from Fth. This study demonstrated that a shared probe microarray designed to detect transcripts in multiple species/subspecies of Francisella enabled comparative transcriptional analyses that may highlight critical differences that underlie the relative pathogenesis of these strains for humans. This strategy could be extended to other closely-related bacterial species for inter-strain and inter-species analyses.
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Affiliation(s)
- Siva T. Sarva
- University of Tennessee Health Science Center, Memphis, TN, United States of America
| | - Robert H. Waldo
- University of Tennessee Health Science Center, Memphis, TN, United States of America
| | - Robert J. Belland
- University of Tennessee Health Science Center, Memphis, TN, United States of America
| | - Karl E. Klose
- South Texas Center for Emerging Infectious Diseases and Dept. of Biology, University of Texas San Antonio, San Antonio, TX, United States of America
- * E-mail:
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Propst CN, Pylypko SL, Blower RJ, Ahmad S, Mansoor M, van Hoek ML. Francisella philomiragia Infection and Lethality in Mammalian Tissue Culture Cell Models, Galleria mellonella, and BALB/c Mice. Front Microbiol 2016; 7:696. [PMID: 27252681 PMCID: PMC4877389 DOI: 10.3389/fmicb.2016.00696] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2015] [Accepted: 04/26/2016] [Indexed: 12/15/2022] Open
Abstract
Francisella (F.) philomiragia is a Gram-negative bacterium with a preference for brackish environments that has been implicated in causing bacterial infections in near-drowning victims. The purpose of this study was to characterize the ability of F. philomiragia to infect cultured mammalian cells, a commonly used invertebrate model, and, finally, to characterize the ability of F. philomiragia to infect BALB/c mice via the pulmonary (intranasal) route of infection. This study shows that F. philomiragia infects J774A.1 murine macrophage cells, HepG2 cells and A549 human Type II alveolar epithelial cells. However, replication rates vary depending on strain at 24 h. F. philomiragia infection after 24 h was found to be cytotoxic in human U937 macrophage-like cells and J774A.1 cells. This is in contrast to the findings that F. philomiragia was non-cytotoxic to human hepatocellular carcinoma cells, HepG2 cells and A549 cells. Differential cytotoxicity is a point for further study. Here, it was demonstrated that F. philomiragia grown in host-adapted conditions (BHI, pH 6.8) is sensitive to levofloxacin but shows increased resistance to the human cathelicidin LL-37 and murine cathelicidin mCRAMP when compared to related the Francisella species, F. tularensis subsp. novicida and F. tularensis subsp. LVS. Previous findings that LL-37 is strongly upregulated in A549 cells following F. tularensis subsp. novicida infection suggest that the level of antimicrobial peptide expression is not sufficient in cells to eradicate the intracellular bacteria. Finally, this study demonstrates that F. philomiragia is lethal in two in vivo models; Galleria mellonella via hemocoel injection, with a LD50 of 1.8 × 103, and BALB/c mice by intranasal infection, with a LD50 of 3.45 × 103. In conclusion, F. philomiragia may be a useful model organism to study the genus Francisella, particularly for those researchers with interest in studying microbial ecology or environmental strains of Francisella. Additionally, the Biosafety level 2 status of F. philomiragia makes it an attractive model for virulence and pathogenesis studies.
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Affiliation(s)
- Crystal N Propst
- School of Systems Biology, George Mason University, Manassas, VA USA
| | | | - Ryan J Blower
- School of Systems Biology, George Mason University, Manassas, VA USA
| | - Saira Ahmad
- School of Systems Biology, George Mason University, Manassas, VA USA
| | | | - Monique L van Hoek
- School of Systems Biology, George Mason University, Manassas, VAUSA; National Center for Biodefense and Infectious Diseases, George Mason University, Manassas, VAUSA
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22
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Qin A, Zhang Y, Clark ME, Moore EA, Rabideau MM, Moreau GB, Mann BJ. Components of the type six secretion system are substrates of Francisella tularensis Schu S4 DsbA-like FipB protein. Virulence 2016; 7:882-894. [PMID: 27028889 PMCID: PMC5160417 DOI: 10.1080/21505594.2016.1168550] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
FipB, an essential virulence factor in the highly virulent Schu S4 strain of F. tularensis subsp. tularensis, shares sequence similarity with Disulfide Bond formation (Dsb) proteins, which can have oxidoreductase, isomerase, or chaperone activity. To further explore FipB's role in virulence potential substrates were identified by co-purification and 2D gel electrophoresis, followed by protein sequencing using mass spectrometry. A total of 119 potential substrates were identified. Proteins with predicted enzymatic activity were prevalent, and there were 19 proteins that had been previously identified as impacting virulence. Among the potential substrates were IglC, IglB, and PdpB, three components of the Francisella Type Six Secretion System (T6SS), which is also essential for virulence. T6SS are widespread in Gram-negative pathogens, but have not been reported to be dependent on Dsb-like proteins for assembly or function. The presented results suggest that FipB affects IglB and IglC substrates differently. In a fipB mutant there were differences in free sulfhydryl accessibility of IglC, but not IglB, when compared to wild-type bacteria. However, for both proteins FipB appears to act as a chaperone that facilitates proper folding and conformation. Understanding the role FipB plays the assembly and structure in this T6SS may reveal critical aspects of assembly that are common and novel among this widely distributed class of secretion systems.
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Affiliation(s)
- Aiping Qin
- a Department of Medicine , Division of Infectious Diseases, University of Virginia , Charlottesville , VA , USA
| | - Yan Zhang
- a Department of Medicine , Division of Infectious Diseases, University of Virginia , Charlottesville , VA , USA
| | - Melinda E Clark
- a Department of Medicine , Division of Infectious Diseases, University of Virginia , Charlottesville , VA , USA
| | - Emily A Moore
- a Department of Medicine , Division of Infectious Diseases, University of Virginia , Charlottesville , VA , USA
| | - Meaghan M Rabideau
- a Department of Medicine , Division of Infectious Diseases, University of Virginia , Charlottesville , VA , USA
| | - G Brett Moreau
- a Department of Medicine , Division of Infectious Diseases, University of Virginia , Charlottesville , VA , USA
| | - Barbara J Mann
- a Department of Medicine , Division of Infectious Diseases, University of Virginia , Charlottesville , VA , USA
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23
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Lo KY, Visram S, Vogl AW, Shen CLJ, Guttman JA. Morphological analysis of Francisella novicida epithelial cell infections in the absence of functional FipA. Cell Tissue Res 2016; 363:449-59. [PMID: 26239909 DOI: 10.1007/s00441-015-2246-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2015] [Accepted: 06/22/2015] [Indexed: 12/16/2022]
Abstract
Francisella novicida is a surrogate pathogen commonly used to study infections by the potential bioterrorism agent, Francisella tularensis. One of the primary sites of Francisella infections is the liver where >90% of infected cells are hepatocytes. It is known that once Francisella enter cells it occupies a membrane-bound compartment, the Francisella-containing vacuole (FCV), from which it rapidly escapes to replicate in the cytosol. Recent work examining the Francisella disulfide bond formation (Dsb) proteins, FipA and FipB, have demonstrated that these proteins are important during the Francisella infection process; however, details as to how the infections are altered in epithelial cells have remained elusive. To identify the stage of the infections where these Dsbs might act during epithelial infections, we exploited a hepatocyte F. novicida infection model that we recently developed. We found that F. novicida ΔfipA-infected hepatocytes contained bacteria clustered within lysosome-associated membrane protein 1-positive FCVs, suggesting that FipA is involved in the escape of F. novicida from its vacuole. Our morphological evidence provides a tangible link as to how Dsb FipA can influence Francisella infections.
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Affiliation(s)
- Karen Y Lo
- Department of Biological Sciences, Centre for Cell Biology, Development, and Disease, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia, V5A 1S6, Canada
| | - Shyanne Visram
- Department of Biological Sciences, Centre for Cell Biology, Development, and Disease, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia, V5A 1S6, Canada
| | - A Wayne Vogl
- Department of Cellular and Physiological Sciences, Faculty of Medicine, University of British Columbia, 2350 Health Sciences Mall, Vancouver, V6T 1Z3, British Columbia, Canada
| | - Chiao Ling Jennifer Shen
- Department of Biological Sciences, Centre for Cell Biology, Development, and Disease, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia, V5A 1S6, Canada
| | - Julian A Guttman
- Department of Biological Sciences, Centre for Cell Biology, Development, and Disease, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia, V5A 1S6, Canada.
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24
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Rowe HM, Huntley JF. From the Outside-In: The Francisella tularensis Envelope and Virulence. Front Cell Infect Microbiol 2015; 5:94. [PMID: 26779445 PMCID: PMC4688374 DOI: 10.3389/fcimb.2015.00094] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2015] [Accepted: 12/07/2015] [Indexed: 12/20/2022] Open
Abstract
Francisella tularensis is a highly-infectious bacterium that causes the rapid, and often lethal disease, tularemia. Many studies have been performed to identify and characterize the virulence factors that F. tularensis uses to infect a wide variety of hosts and host cell types, evade immune defenses, and induce severe disease and death. This review focuses on the virulence factors that are present in the F. tularensis envelope, including capsule, LPS, outer membrane, periplasm, inner membrane, secretion systems, and various molecules in each of aforementioned sub-compartments. Whereas, no single bacterial molecule or molecular complex single-handedly controls F. tularensis virulence, we review here how diverse bacterial systems work in conjunction to subvert the immune system, attach to and invade host cells, alter phagosome/lysosome maturation pathways, replicate in host cells without being detected, inhibit apoptosis, and induce host cell death for bacterial release and infection of adjacent cells. Given that the F. tularensis envelope is the outermost layer of the bacterium, we highlight herein how many of these molecules directly interact with the host to promote infection and disease. These and future envelope studies are important to advance our collective understanding of F. tularensis virulence mechanisms and offer targets for future vaccine development efforts.
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Affiliation(s)
- Hannah M Rowe
- Department of Medical Microbiology and Immunology, University of Toledo College of Medicine and Life Sciences Toledo, OH, USA
| | - Jason F Huntley
- Department of Medical Microbiology and Immunology, University of Toledo College of Medicine and Life Sciences Toledo, OH, USA
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25
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Aloni-Grinstein R, Shifman O, Lazar S, Steinberger-Levy I, Maoz S, Ber R. A rapid real-time quantitative PCR assay to determine the minimal inhibitory extracellular concentration of antibiotics against an intracellular Francisella tularensis Live Vaccine Strain. Front Microbiol 2015; 6:1213. [PMID: 26579112 PMCID: PMC4630301 DOI: 10.3389/fmicb.2015.01213] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2015] [Accepted: 10/19/2015] [Indexed: 12/17/2022] Open
Abstract
Francisella tularensis is a highly virulent facultative intracellular bacterium. The lack of a safe and efficient vaccine makes antibiotics the preferred treatment. F. tularensis antibiotic susceptibility tests are based on the in vitro standard CLSI-approved microdilution method for determining the MIC. However, limited data are available regarding the minimal inhibitory extracellular concentration (MIEC) needed to eradicate intracellular bacteria. Here, we evaluated the MIEC values of various WHO-recommended antibiotics and compared the MIEC values to the established MICs. We describe a rapid 3-h quantitative PCR (qPCR) intracellular antibiogram assay, which yields comparable MIEC values to those obtained by the classical 72-h cfu assay. This rapid qPCR assay is highly advantageous in light of the slow growth rates of F. tularensis. Our results showed that the MIECs obtained for doxycycline, chloramphenicol and ciprofloxacin were indicative of intracellular activity. Gentamicin was not effective against intracellular bacteria for at least 32 h post treatment, raising the question of whether slow-penetrating gentamicin should be used for certain stages of the disease. We suggest that the qPCR intracellular antibiogram assay may be used to screen for potentially active antibiotics against intracellular F. tularensis as well as to detect strains with acquired resistance to recommended antibiotics.
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Affiliation(s)
- Ronit Aloni-Grinstein
- Department of Biochemistry and Molecular Genetics, Israel Institute for Biological Research Ness Ziona, Israel
| | - Ohad Shifman
- Department of Biochemistry and Molecular Genetics, Israel Institute for Biological Research Ness Ziona, Israel
| | - Shlomi Lazar
- Department of Pharmacology, Israel Institute for Biological Research Ness Ziona, Israel
| | - Ida Steinberger-Levy
- Department of Biochemistry and Molecular Genetics, Israel Institute for Biological Research Ness Ziona, Israel
| | - Sharon Maoz
- Department of Biochemistry and Molecular Genetics, Israel Institute for Biological Research Ness Ziona, Israel
| | - Raphael Ber
- Department of Biochemistry and Molecular Genetics, Israel Institute for Biological Research Ness Ziona, Israel
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26
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Brissac T, Ziveri J, Ramond E, Tros F, Kock S, Dupuis M, Brillet M, Barel M, Peyriga L, Cahoreau E, Charbit A. Gluconeogenesis, an essential metabolic pathway for pathogenic Francisella. Mol Microbiol 2015; 98:518-34. [PMID: 26192619 DOI: 10.1111/mmi.13139] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/16/2015] [Indexed: 01/23/2023]
Abstract
Intracellular multiplication and dissemination of the infectious bacterial pathogen Francisella tularensis implies the utilization of multiple host-derived nutrients. Here, we demonstrate that gluconeogenesis constitutes an essential metabolic pathway in Francisella pathogenesis. Indeed, inactivation of gene glpX, encoding the unique fructose 1,6-bisphosphatase of Francisella, severely impaired bacterial intracellular multiplication when cells were supplemented by gluconeogenic substrates such as glycerol or pyruvate. The ΔglpX mutant also showed a severe virulence defect in the mouse model, confirming the importance of this pathway during the in vivo life cycle of the pathogen. Isotopic profiling revealed the major role of the Embden-Meyerhof (glycolysis) pathway in glucose catabolism in Francisella and confirmed the importance of glpX in gluconeogenesis. Altogether, the data presented suggest that gluconeogenesis allows Francisella to cope with the limiting glucose availability it encounters during its infectious cycle by relying on host amino acids. Hence, targeting the gluconeogenic pathway might constitute an interesting therapeutic approach against this pathogen.
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Affiliation(s)
- Terry Brissac
- Université Paris Descartes, Sorbonne Paris Cité, Bâtiment Leriche, Paris, France.,INSERM U1151 - CNRS UMR 8253, Institut Necker-Enfants Malades, Equipe 11: Pathogénie des Infections Systémiques, Paris, France
| | - Jason Ziveri
- Université Paris Descartes, Sorbonne Paris Cité, Bâtiment Leriche, Paris, France.,INSERM U1151 - CNRS UMR 8253, Institut Necker-Enfants Malades, Equipe 11: Pathogénie des Infections Systémiques, Paris, France
| | - Elodie Ramond
- Université Paris Descartes, Sorbonne Paris Cité, Bâtiment Leriche, Paris, France.,INSERM U1151 - CNRS UMR 8253, Institut Necker-Enfants Malades, Equipe 11: Pathogénie des Infections Systémiques, Paris, France
| | - Fabiola Tros
- Université Paris Descartes, Sorbonne Paris Cité, Bâtiment Leriche, Paris, France.,INSERM U1151 - CNRS UMR 8253, Institut Necker-Enfants Malades, Equipe 11: Pathogénie des Infections Systémiques, Paris, France
| | - Stephanie Kock
- Université Paris Descartes, Sorbonne Paris Cité, Bâtiment Leriche, Paris, France.,INSERM U1151 - CNRS UMR 8253, Institut Necker-Enfants Malades, Equipe 11: Pathogénie des Infections Systémiques, Paris, France
| | - Marion Dupuis
- Université Paris Descartes, Sorbonne Paris Cité, Bâtiment Leriche, Paris, France.,INSERM U1151 - CNRS UMR 8253, Institut Necker-Enfants Malades, Equipe 11: Pathogénie des Infections Systémiques, Paris, France
| | - Magali Brillet
- Université Paris Descartes, Sorbonne Paris Cité, Bâtiment Leriche, Paris, France.,INSERM U1151 - CNRS UMR 8253, Institut Necker-Enfants Malades, Equipe 11: Pathogénie des Infections Systémiques, Paris, France
| | - Monique Barel
- Université Paris Descartes, Sorbonne Paris Cité, Bâtiment Leriche, Paris, France.,INSERM U1151 - CNRS UMR 8253, Institut Necker-Enfants Malades, Equipe 11: Pathogénie des Infections Systémiques, Paris, France
| | - Lindsay Peyriga
- Université de Toulouse, INSA, UPS, INP, LISBP, 135 Avenue de Rangueil, Toulouse, 31077, France.,INRA, UMR792, Ingénierie des Systèmes Biologiques et des Procédés, Toulouse, 31400, France.,CNRS, UMR5504, Toulouse, 31400, France
| | - Edern Cahoreau
- Université de Toulouse, INSA, UPS, INP, LISBP, 135 Avenue de Rangueil, Toulouse, 31077, France.,INRA, UMR792, Ingénierie des Systèmes Biologiques et des Procédés, Toulouse, 31400, France.,CNRS, UMR5504, Toulouse, 31400, France
| | - Alain Charbit
- Université Paris Descartes, Sorbonne Paris Cité, Bâtiment Leriche, Paris, France.,INSERM U1151 - CNRS UMR 8253, Institut Necker-Enfants Malades, Equipe 11: Pathogénie des Infections Systémiques, Paris, France
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27
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The Identification of Genes Important in Pseudomonas syringae pv. phaseolicola Plant Colonisation Using In Vitro Screening of Transposon Libraries. PLoS One 2015; 10:e0137355. [PMID: 26325299 PMCID: PMC4556710 DOI: 10.1371/journal.pone.0137355] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2015] [Accepted: 08/15/2015] [Indexed: 01/18/2023] Open
Abstract
The bacterial plant pathogen Pseudomonas syringae pv. phaseolicola (Pph) colonises the surface of common bean plants before moving into the interior of plant tissue, via wounds and stomata. In the intercellular spaces the pathogen proliferates in the apoplastic fluid and forms microcolonies (biofilms) around plant cells. If the pathogen can suppress the plant’s natural resistance response, it will cause halo blight disease. The process of resistance suppression is fairly well understood, but the mechanisms used by the pathogen in colonisation are less clear. We hypothesised that we could apply in vitro genetic screens to look for changes in motility, colony formation, and adhesion, which are proxies for infection, microcolony formation and cell adhesion. We made transposon (Tn) mutant libraries of Pph strains 1448A and 1302A and found 106/1920 mutants exhibited alterations in colony morphology, motility and biofilm formation. Identification of the insertion point of the Tn identified within the genome highlighted, as expected, a number of altered motility mutants bearing mutations in genes encoding various parts of the flagellum. Genes involved in nutrient biosynthesis, membrane associated proteins, and a number of conserved hypothetical protein (CHP) genes were also identified. A mutation of one CHP gene caused a positive increase in in planta bacterial growth. This rapid and inexpensive screening method allows the discovery of genes important for in vitro traits that can be correlated to roles in the plant interaction.
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28
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Wu X, Ren G, Huntley JF. Generating Isogenic Deletions (Knockouts) in Francisella tularensis, a Highly-infectious and Fastidious Gram-negative Bacterium. Bio Protoc 2015; 5:e1500. [PMID: 26137499 PMCID: PMC4484883 DOI: 10.21769/bioprotoc.1500] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2023] Open
Abstract
Generating bacterial gene deletion mutants, also known as knockouts (KOs), is a powerful tool to investigate individual gene functions. However, fastidious bacteria such as Francisella tularensis (F. tularensis) often are difficult to genetically manipulate. Indeed, many different approaches have been tested to generate F. tularensis mutants. First, Tn5-based EZ::TN transposons have been successfully used to generate transposon libraries in F. tularensis (Qin and Mann, 2006; Weiss et al., 2007). However, creating a comprehensive transposon library with saturating mutations can be laborious, screening for gene disruption requires high-throughput assays where known phenotypes can be measured, and transposons may not completely inactivate the gene of interest or may alter downstream gene expression. Second, group II introns (also referred to as Targetron) have been used to inactivate F. tularensis genes of interest (Rodriguez et al., 2008; Rodriguez et al., 2009). Targetron functions by forming a complex between plasmid-encoded RNA and chromosomal DNA, followed by group II intron insertion into the gene of interest. The main advantage of Targetron is that it does not require an antibiotic resistance marker. However, as noted for transposons, targetron gene insertions may not eliminate all gene functions or may affect downstream gene expression. Third, homologous recombination can be used to completely replace the chromosomal target gene with a selectable marker, such as an antibiotic resistance marker. This classical genetic technique has been used in many F. tularensis studies (Ramakrishnan et al., 2008; Ren et al., 2014; Mohapatra et al., 2008; Robertson et al., 2013). To accomplish this, a suicide plasmid is engineered to include a selectable marker flanked by regions upstream and downstream of the gene of interest. This KO plasmid can be delivered into host bacteria by many methods, including electroporation, chemical transformation, or conjugation. Here, we describe an optimized procedure to generate KO plasmid constructs, use E. coli to conjugatively transfer the plasmid into F. tularensis, select for F. tularensis KOs using a series of kanamycin-, hygromycin-, and sucrose-resistance steps, and confirm that the gene of interest has been deleted (general overview of the knockout protocol diagramed in Figure 1). This optimized procedure is relatively simple, rapid, and, more importantly, includes a series of both positive and negative selection steps to increase the chances of deleting a target gene from F. tularensis.
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Affiliation(s)
- Xiaojun Wu
- Department of Medical Microbiology and Immunology, University of Toledo College of Medicine and Life Sciences, Toledo, USA
| | - Guoping Ren
- Department of Medical Microbiology and Immunology, University of Toledo College of Medicine and Life Sciences, Toledo, USA
| | - Jason F. Huntley
- Department of Medical Microbiology and Immunology, University of Toledo College of Medicine and Life Sciences, Toledo, USA
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29
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Microinjection of Francisella tularensis and Listeria monocytogenes reveals the importance of bacterial and host factors for successful replication. Infect Immun 2015; 83:3233-42. [PMID: 26034213 DOI: 10.1128/iai.00416-15] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2015] [Accepted: 05/26/2015] [Indexed: 11/20/2022] Open
Abstract
Certain intracellular bacteria use the host cell cytosol as the replicative niche. Although it has been hypothesized that the successful exploitation of this compartment requires a unique metabolic adaptation, supportive evidence is lacking. For Francisella tularensis, many genes of the Francisella pathogenicity island (FPI) are essential for intracellular growth, and therefore, FPI mutants are useful tools for understanding the prerequisites of intracytosolic replication. We compared the growth of bacteria taken up by phagocytic or nonphagocytic cells with that of bacteria microinjected directly into the host cytosol, using the live vaccine strain (LVS) of F. tularensis; five selected FPI mutants thereof, i.e., ΔiglA, ΔiglÇ ΔiglG, ΔiglI, and ΔpdpE strains; and Listeria monocytogenes. After uptake in bone marrow-derived macrophages (BMDM), ASC(-/-) BMDM, MyD88(-/-) BMDM, J774 cells, or HeLa cells, LVS, ΔpdpE and ΔiglG mutants, and L. monocytogenes replicated efficiently in all five cell types, whereas the ΔiglA and ΔiglC mutants showed no replication. After microinjection, all 7 strains showed effective replication in J774 macrophages, ASC(-/-) BMDM, and HeLa cells. In contrast to the rapid replication in other cell types, L. monocytogenes showed no replication in MyD88(-/-) BMDM and LVS showed no replication in either BMDM or MyD88(-/-) BMDM after microinjection. Our data suggest that the mechanisms of bacterial uptake as well as the permissiveness of the cytosolic compartment per se are important factors for the intracytosolic replication. Notably, none of the investigated FPI proteins was found to be essential for intracytosolic replication after microinjection.
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30
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Identifying Francisella tularensis genes required for growth in host cells. Infect Immun 2015; 83:3015-25. [PMID: 25987704 DOI: 10.1128/iai.00004-15] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2015] [Accepted: 05/06/2015] [Indexed: 12/22/2022] Open
Abstract
Francisella tularensis is a highly virulent Gram-negative intracellular pathogen capable of infecting a vast diversity of hosts, ranging from amoebae to humans. A hallmark of F. tularensis virulence is its ability to quickly grow to high densities within a diverse set of host cells, including, but not limited to, macrophages and epithelial cells. We developed a luminescence reporter system to facilitate a large-scale transposon mutagenesis screen to identify genes required for growth in macrophage and epithelial cell lines. We screened 7,454 individual mutants, 269 of which exhibited reduced intracellular growth. Transposon insertions in the 269 growth-defective strains mapped to 68 different genes. FTT_0924, a gene of unknown function but highly conserved among Francisella species, was identified in this screen to be defective for intracellular growth within both macrophage and epithelial cell lines. FTT_0924 was required for full Schu S4 virulence in a murine pulmonary infection model. The ΔFTT_0924 mutant bacterial membrane is permeable when replicating in hypotonic solution and within macrophages, resulting in strongly reduced viability. The permeability and reduced viability were rescued when the mutant was grown in a hypertonic solution, indicating that FTT_0924 is required for resisting osmotic stress. The ΔFTT_0924 mutant was also significantly more sensitive to β-lactam antibiotics than Schu S4. Taken together, the data strongly suggest that FTT_0924 is required for maintaining peptidoglycan integrity and virulence.
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31
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Barel M, Ramond E, Gesbert G, Charbit A. The complex amino acid diet of Francisella in infected macrophages. Front Cell Infect Microbiol 2015; 5:9. [PMID: 25705612 PMCID: PMC4319460 DOI: 10.3389/fcimb.2015.00009] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2014] [Accepted: 01/14/2015] [Indexed: 12/16/2022] Open
Abstract
Francisella tularensis, the agent of the zoonotic disease tularemia, is a highly infectious bacterium for a large number of animal species and can be transmitted to humans by various means. The bacterium is able to infect a variety of cell types but replicates in mammalian hosts mainly in the cytosol of infected macrophages. In order to resist the stressful and nutrient-restricted intracellular environments, it encounters during its systemic dissemination, Francisella has developed dedicated stress resistance mechanisms and adapted its metabolic and nutritional needs. Recent data form our laboratory and from several other groups have shown that Francisella simultaneously relies on multiple host amino acid sources during its intracellular life cycle. This review will summarize how intracellular Francisella use different amino acid sources, and their role in phagosomal escape and/or cytosolic multiplication and systemic dissemination. We will first summarize the data that we have obtained on two amino acid transporters involved in Francisella phagosomal escape and cytosolic multiplication i.e., the glutamate transporter GadC and the asparagine transporter AnsP, respectively. The specific contribution of glutamate and asparagine to the physiology of the bacterium will be evoked. Then, we will discuss how Francisella has adapted to obtain and utilize host amino acid resources, and notably the contribution of host transporters and autophagy process in the establishment of a nutrient-replete intracellular niche.
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Affiliation(s)
- Monique Barel
- Université Paris Descartes, Sorbonne Paris Cité Paris, France ; INSERM U1151 - Centre National de la Recherche Scientifique UMR 8253, Institut Necker-Enfants Malades Paris, France
| | - Elodie Ramond
- Université Paris Descartes, Sorbonne Paris Cité Paris, France ; INSERM U1151 - Centre National de la Recherche Scientifique UMR 8253, Institut Necker-Enfants Malades Paris, France
| | - Gael Gesbert
- Université Paris Descartes, Sorbonne Paris Cité Paris, France ; INSERM U1151 - Centre National de la Recherche Scientifique UMR 8253, Institut Necker-Enfants Malades Paris, France
| | - Alain Charbit
- Université Paris Descartes, Sorbonne Paris Cité Paris, France ; INSERM U1151 - Centre National de la Recherche Scientifique UMR 8253, Institut Necker-Enfants Malades Paris, France
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32
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Importance of branched-chain amino acid utilization in Francisella intracellular adaptation. Infect Immun 2014; 83:173-83. [PMID: 25332124 DOI: 10.1128/iai.02579-14] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Intracellular bacterial pathogens have adapted their metabolism to optimally utilize the nutrients available in infected host cells. We recently reported the identification of an asparagine transporter required specifically for cytosolic multiplication of Francisella. In the present work, we characterized a new member of the major super family (MSF) of transporters, involved in isoleucine uptake. We show that this transporter (here designated IleP) plays a critical role in intracellular metabolic adaptation of Francisella. Inactivation of IleP severely impaired intracellular F. tularensis subsp. novicida multiplication in all cell types tested and reduced bacterial virulence in the mouse model. To further establish the importance of the ileP gene in F. tularensis pathogenesis, we constructed a chromosomal deletion mutant of ileP (ΔFTL_1803) in the F. tularensis subsp. holarctica live vaccine strain (LVS). Inactivation of IleP in the F. tularensis LVS provoked comparable intracellular growth defects, confirming the critical role of this transporter in isoleucine uptake. The data presented establish, for the first time, the importance of isoleucine utilization for efficient phagosomal escape and cytosolic multiplication of Francisella and suggest that virulent F. tularensis subspecies have lost their branched-chain amino acid biosynthetic pathways and rely exclusively on dedicated uptake systems. This loss of function is likely to reflect an evolution toward a predominantly intracellular life style of the pathogen. Amino acid transporters should be thus considered major players in the adaptation of intracellular pathogens.
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Characterization of tetratricopeptide repeat-like proteins in Francisella tularensis and identification of a novel locus required for virulence. Infect Immun 2014; 82:5035-48. [PMID: 25245806 DOI: 10.1128/iai.01620-14] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Francisella tularensis is a highly infectious bacterium that causes the potentially lethal disease tularemia. This extremely virulent bacterium is able to replicate in the cytosolic compartments of infected macrophages. To invade macrophages and to cope with their intracellular environment, Francisella requires multiple virulence factors, which are still being identified. Proteins containing tetratricopeptide repeat (TPR)-like domains seem to be promising targets to investigate, since these proteins have been reported to be directly involved in virulence-associated functions of bacterial pathogens. Here, we studied the role of the FTS_0201, FTS_0778, and FTS_1680 genes, which encode putative TPR-like proteins in Francisella tularensis subsp. holarctica FSC200. Mutants defective in protein expression were prepared by TargeTron insertion mutagenesis. We found that the locus FTS_1680 and its ortholog FTT_0166c in the highly virulent Francisella tularensis type A strain SchuS4 are required for proper intracellular replication, full virulence in mice, and heat stress tolerance. Additionally, the FTS_1680-encoded protein was identified as a membrane-associated protein required for full cytopathogenicity in macrophages. Our study thus identifies FTS_1680/FTT_0166c as a new virulence factor in Francisella tularensis.
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Law HT, Sriram A, Fevang C, Nix EB, Nano FE, Guttman JA. IglC and PdpA are important for promoting Francisella invasion and intracellular growth in epithelial cells. PLoS One 2014; 9:e104881. [PMID: 25115488 PMCID: PMC4130613 DOI: 10.1371/journal.pone.0104881] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2014] [Accepted: 07/17/2014] [Indexed: 01/06/2023] Open
Abstract
The highly infectious bacteria, Francisella tularensis, colonize a variety of organs and replicate within both phagocytic as well as non-phagocytic cells, to cause the disease tularemia. These microbes contain a conserved cluster of important virulence genes referred to as the Francisella Pathogenicity Island (FPI). Two of the most characterized FPI genes, iglC and pdpA, play a central role in bacterial survival and proliferation within phagocytes, but do not influence bacterial internalization. Yet, their involvement in non-phagocytic epithelial cell infections remains unexplored. To examine the functions of IglC and PdpA on bacterial invasion and replication during epithelial cell infections, we infected liver and lung epithelial cells with F. novicida and F. tularensis 'Type B' Live Vaccine Strain (LVS) deletion mutants (ΔiglC and ΔpdpA) as well as their respective gene complements. We found that deletion of either gene significantly reduced their ability to invade and replicate in epithelial cells. Gene complementation of iglC and pdpA partially rescued bacterial invasion and intracellular growth. Additionally, substantial LAMP1-association with both deletion mutants was observed up to 12 h suggesting that the absence of IglC and PdpA caused deficiencies in their ability to dissociate from LAMP1-positive Francisella Containing Vacuoles (FCVs). This work provides the first evidence that IglC and PdpA are important pathogenic factors for invasion and intracellular growth of Francisella in epithelial cells, and further highlights the discrete mechanisms involved in Francisella infections between phagocytic and non-phagocytic cells.
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Affiliation(s)
- H. T. Law
- Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Aarati Sriram
- Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Charlotte Fevang
- Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Eli B. Nix
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, British Columbia, Canada
| | - Francis E. Nano
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, British Columbia, Canada
| | - Julian Andrew Guttman
- Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia, Canada
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TolC-dependent modulation of host cell death by the Francisella tularensis live vaccine strain. Infect Immun 2014; 82:2068-78. [PMID: 24614652 DOI: 10.1128/iai.00044-14] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Francisella tularensis is a facultative intracellular, Gram-negative pathogen and the causative agent of tularemia. We previously identified TolC as a virulence factor of the F. tularensis live vaccine strain (LVS) and demonstrated that a ΔtolC mutant exhibits increased cytotoxicity toward host cells and elicits increased proinflammatory responses compared to those of the wild-type (WT) strain. TolC is the outer membrane channel component used by the type I secretion pathway to export toxins and other bacterial virulence factors. Here, we show that the LVS delays activation of the intrinsic apoptotic pathway in a TolC-dependent manner, both during infection of primary macrophages and during organ colonization in mice. The TolC-dependent delay in host cell death is required for F. tularensis to preserve its intracellular replicative niche. We demonstrate that TolC-mediated inhibition of apoptosis is an active process and not due to defects in the structural integrity of the ΔtolC mutant. These findings support a model wherein the immunomodulatory capacity of F. tularensis relies, at least in part, on TolC-secreted effectors. Finally, mice vaccinated with the ΔtolC LVS are protected from lethal challenge and clear challenge doses faster than WT-vaccinated mice, demonstrating that the altered host responses to primary infection with the ΔtolC mutant led to altered adaptive immune responses. Taken together, our data demonstrate that TolC is required for temporal modulation of host cell death during infection by F. tularensis and highlight how shifts in the magnitude and timing of host innate immune responses may lead to dramatic changes in the outcome of infection.
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Jones BD, Faron M, Rasmussen JA, Fletcher JR. Uncovering the components of the Francisella tularensis virulence stealth strategy. Front Cell Infect Microbiol 2014; 4:32. [PMID: 24639953 PMCID: PMC3945745 DOI: 10.3389/fcimb.2014.00032] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2013] [Accepted: 02/17/2014] [Indexed: 12/21/2022] Open
Abstract
Over the last decade, studies on the virulence of the highly pathogenic intracellular bacterial pathogen Francisella tularensis have increased dramatically. The organism produces an inert LPS, a capsule, escapes the phagosome to grow in the cytosol (FPI genes mediate phagosomal escape) of a variety of host cell types that include epithelial, endothelial, dendritic, macrophage, and neutrophil. This review focuses on the work that has identified and characterized individual virulence factors of this organism and we hope to highlight how these factors collectively function to produce the pathogenic strategy of this pathogen. In addition, several recent studies have been published characterizing F. tularensis mutants that induce host immune responses not observed in wild type F. tularensis strains that can induce protection against challenge with virulent F. tularensis. As more detailed studies with attenuated strains are performed, it will be possible to see how host models develop acquired immunity to Francisella. Collectively, detailed insights into the mechanisms of virulence of this pathogen are emerging that will allow the design of anti-infective strategies.
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Affiliation(s)
- Bradley D Jones
- Department of Microbiology, The University of Iowa Carver College of Medicine Iowa City, IA, USA ; The Genetics Program, The University of Iowa Carver College of Medicine Iowa City, IA, USA ; The Midwest Regional Center for Excellence in Biodefense and Emerging Infectious Disease Research, Washington University St. Louis, MO, USA
| | - Matthew Faron
- The Genetics Program, The University of Iowa Carver College of Medicine Iowa City, IA, USA
| | - Jed A Rasmussen
- Department of Microbiology, The University of Iowa Carver College of Medicine Iowa City, IA, USA
| | - Joshua R Fletcher
- The Genetics Program, The University of Iowa Carver College of Medicine Iowa City, IA, USA
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Gillette DD, Tridandapani S, Butchar JP. Monocyte/macrophage inflammatory response pathways to combat Francisella infection: possible therapeutic targets? Front Cell Infect Microbiol 2014; 4:18. [PMID: 24600590 PMCID: PMC3930869 DOI: 10.3389/fcimb.2014.00018] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2013] [Accepted: 02/02/2014] [Indexed: 01/05/2023] Open
Abstract
Francisella tularensis can bypass and suppress host immune responses, even to the point of manipulating immune cell phenotypes and intercellular inflammatory networks. Strengthening these responses such that immune cells more readily identify and destroy the bacteria is likely to become a viable (and perhaps necessary) strategy for combating infections with Francisella, especially given the likelihood of antibiotic resistance in the foreseeable future. Monocytes and macrophages offer a niche wherein Francisella can invade and replicate, resulting in substantially higher bacterial load that can overcome the host. As such, understanding their responses to Francisella may uncover potential avenues of therapy that could promote a lowering of bacterial burden and clearance of infection. These response pathways include Toll-like Receptor 2 (TLR2), the caspase-1 inflammasome, Interferons, NADPH oxidase, Phosphatidylinositide 3-kinase (PI3K), and the Ras pathway. In this review we summarize the literature pertaining to the roles of these pathways during Francisella infection, with an emphasis on monocyte/macrophage responses. The therapeutic targeting of one or more such pathways may ultimately become a valuable tool for the treatment of tularemia, and several possibilities are discussed.
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Affiliation(s)
- Devyn D Gillette
- Department of Internal Medicine, Wexner Medical Center, The Ohio State University Columbus, OH, USA
| | - Susheela Tridandapani
- Department of Internal Medicine, Wexner Medical Center, The Ohio State University Columbus, OH, USA
| | - Jonathan P Butchar
- Department of Internal Medicine, Wexner Medical Center, The Ohio State University Columbus, OH, USA
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Gesbert G, Ramond E, Rigard M, Frapy E, Dupuis M, Dubail I, Barel M, Henry T, Meibom K, Charbit A. Asparagine assimilation is critical for intracellular replication and dissemination of Francisella. Cell Microbiol 2013; 16:434-49. [PMID: 24134488 DOI: 10.1111/cmi.12227] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2013] [Revised: 10/10/2013] [Accepted: 10/11/2013] [Indexed: 12/28/2022]
Abstract
In order to develop a successful infectious cycle, intracellular bacterial pathogens must be able to adapt their metabolism to optimally utilize the nutrients available in the cellular compartments and tissues where they reside. Francisella tularensis, the agent of the zoonotic disease tularaemia, is a highly infectious bacterium for a large number of animal species. This bacterium replicates in its mammalian hosts mainly in the cytosol of infected macrophages. We report here the identification of a novel amino acid transporter of the major facilitator superfamily of secondary transporters that is required for bacterial intracellular multiplication and systemic dissemination. We show that inactivation of this transporter does not affect phagosomal escape but prevents multiplication in the cytosol of all cell types tested. Remarkably, the intracellular growth defect of the mutant was fully and specifically reversed by addition of asparagine or asparagine-containing dipeptides as well as by simultaneous addition of aspartic acid and ammonium. Importantly, bacterial virulence was also restored in vivo, in the mouse model, by asparagine supplementation. This work unravels thus, for the first time, the importance of asparagine for cytosolicmultiplication of Francisella. Amino acid transporters are likely to constitute underappreciated players in bacterial intracellular parasitism.
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Affiliation(s)
- Gael Gesbert
- Université Paris Descartes, Sorbonne Paris Cité, Bâtiment Leriche, 96 rue Didot 75993, Paris, Cedex 14, France; INSERM, U1002, Unité de Pathogénie des Infections Systémiques, Paris, France
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Synthetic promoters functional in Francisella novicida and Escherichia coli. Appl Environ Microbiol 2013; 80:226-34. [PMID: 24141126 DOI: 10.1128/aem.02793-13] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In this work, we describe the identification of synthetic, controllable promoters that function in the bacterial pathogen Francisella novicida, a model facultative intracellular pathogen. Synthetic DNA fragments consisting of the tetracycline operator (tetO) flanked by a random nucleotide sequence were inserted into a Francisella novicida shuttle plasmid upstream of a promoterless artificial operon containing the reporter genes cat and lacZ. Fragments able to promote transcription were selected for based on their ability to drive expression of the cat gene, conferring chloramphenicol resistance. Promoters of various strengths were found, many of which were repressed in the presence of the tetracycline repressor (TetR) and promoted transcription only in the presence of the TetR inducer anhydrotetracycline. A subset of both constitutive and inducible synthetic promoters were characterized to find their induction ratios and to identify their transcription start sites. In cases where tetO was located between or downstream of the -10 and -35 regions of the promoter, control by TetR was observed. If the tetO region was upstream of the -35 region by more than 9 bp, it did not confer TetR control. We found that three of three promoters isolated in F. novicida functioned at a comparable level in E. coli; however, none of the 10 promoters isolated in E. coli functioned at a significant level in F. novicida. Our results allowed us to isolate minimal F. novicida promoters of 47 and 48 bp in length.
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Bent ZW, Brazel DM, Tran-Gyamfi MB, Hamblin RY, VanderNoot VA, Branda SS. Use of a capture-based pathogen transcript enrichment strategy for RNA-Seq analysis of the Francisella tularensis LVS transcriptome during infection of murine macrophages. PLoS One 2013; 8:e77834. [PMID: 24155975 PMCID: PMC3796476 DOI: 10.1371/journal.pone.0077834] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2013] [Accepted: 09/09/2013] [Indexed: 12/17/2022] Open
Abstract
Francisella tularensis is a zoonotic intracellular pathogen that is capable of causing potentially fatal human infections. Like all successful bacterial pathogens, F. tularensis rapidly responds to changes in its environment during infection of host cells, and upon encountering different microenvironments within those cells. This ability to appropriately respond to the challenges of infection requires rapid and global shifts in gene expression patterns. In this study, we use a novel pathogen transcript enrichment strategy and whole transcriptome sequencing (RNA-Seq) to perform a detailed characterization of the rapid and global shifts in F. tularensis LVS gene expression during infection of murine macrophages. We performed differential gene expression analysis on all bacterial genes at two key stages of infection: phagosomal escape, and cytosolic replication. By comparing the F. tularensis transcriptome at these two stages of infection to that of the bacteria grown in culture, we were able to identify sets of genes that are differentially expressed over the course of infection. This analysis revealed the temporally dynamic expression of a number of known and putative transcriptional regulators and virulence factors, providing insight into their role during infection. In addition, we identified several F. tularensis genes that are significantly up-regulated during infection but had not been previously identified as virulence factors. These unknown genes may make attractive therapeutic or vaccine targets.
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Affiliation(s)
- Zachary W. Bent
- Sandia National Laboratories, Livermore, California, United States of America
- * E-mail:
| | - David M. Brazel
- Sandia National Laboratories, Livermore, California, United States of America
| | - Mary B. Tran-Gyamfi
- Sandia National Laboratories, Livermore, California, United States of America
| | - Rachelle Y. Hamblin
- Sandia National Laboratories, Livermore, California, United States of America
| | | | - Steven S. Branda
- Sandia National Laboratories, Livermore, California, United States of America
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Chong A, Child R, Wehrly TD, Rockx-Brouwer D, Qin A, Mann BJ, Celli J. Structure-Function Analysis of DipA, a Francisella tularensis Virulence Factor Required for Intracellular Replication. PLoS One 2013; 8:e67965. [PMID: 23840797 PMCID: PMC3694160 DOI: 10.1371/journal.pone.0067965] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2013] [Accepted: 05/23/2013] [Indexed: 12/26/2022] Open
Abstract
Francisella tularensis is a highly infectious bacterium whose virulence relies on its ability to rapidly reach the macrophage cytosol and extensively replicate in this compartment. We previously identified a novel Francisella virulence factor, DipA (FTT0369c), which is required for intramacrophage proliferation and survival, and virulence in mice. DipA is a 353 amino acid protein with a Sec-dependent signal peptide, four Sel1-like repeats (SLR), and a C-terminal coiled-coil (CC) domain. Here, we determined through biochemical and localization studies that DipA is a membrane-associated protein exposed on the surface of the prototypical F. tularensis subsp. tularensis strain SchuS4 during macrophage infection. Deletion and substitution mutagenesis showed that the CC domain, but not the SLR motifs, of DipA is required for surface exposure on SchuS4. Complementation of the dipA mutant with either DipA CC or SLR domain mutants did not restore intracellular growth of Francisella, indicating that proper localization and the SLR domains are required for DipA function. Co-immunoprecipitation studies revealed interactions with the Francisella outer membrane protein FopA, suggesting that DipA is part of a membrane-associated complex. Altogether, our findings indicate that DipA is positioned at the host–pathogen interface to influence the intracellular fate of this pathogen.
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Affiliation(s)
- Audrey Chong
- Laboratory of Intracellular Parasites, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, United States of America
- * E-mail:
| | - Robert Child
- Laboratory of Intracellular Parasites, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, United States of America
| | - Tara D. Wehrly
- Laboratory of Intracellular Parasites, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, United States of America
| | - Dedeke Rockx-Brouwer
- Laboratory of Intracellular Parasites, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, United States of America
| | - Aiping Qin
- Department of Medicine, University of Virginia, Charlottesville, Virginia, United States of America
| | - Barbara J. Mann
- Department of Medicine, University of Virginia, Charlottesville, Virginia, United States of America
- Department of Microbiology, University of Virginia, Charlottesville, Virginia, United States of America
| | - Jean Celli
- Laboratory of Intracellular Parasites, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, United States of America
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Live attenuated tularemia vaccines: recent developments and future goals. Vaccine 2013; 31:3485-91. [PMID: 23764535 DOI: 10.1016/j.vaccine.2013.05.096] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2013] [Revised: 05/20/2013] [Accepted: 05/24/2013] [Indexed: 12/24/2022]
Abstract
In the aftermath of the 2001 anthrax attacks in the U.S., numerous efforts were made to increase the level of preparedness against a biological attack both in the US and worldwide. As a result, there has been an increase in research interest in the development of vaccines and other countermeasures against a number of agents with the potential to be used as biological weapons. One such agent, Francisella tularensis, has been the subject of a surge in the level of research being performed, leading to a substantial increase in knowledge of the pathogenic mechanisms of the organism and the induced immune responses. This information has facilitated the development of multiple new Francisella vaccine candidates. Herein we review the latest live attenuated F. tularensis vaccine efforts. Historically, live attenuated vaccines have demonstrated the greatest degree of success in protection against tularemia and the greatest promise in recent efforts to develop of a fully protective vaccine. This review summarizes recent live attenuated Francisella vaccine candidates and the lessons learned from those studies, with the goal of collating known characteristics associated with successful attenuation, immunogenicity, and protection.
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Abstract
Francisella tularensis, the bacterial cause of tularemia, infects the liver and replicates in hepatocytes in vivo and in vitro. However, the factors that govern adaptation of F. tularensis to the intrahepatocytic niche have not been identified. Using cDNA microarrays, we determined the transcriptional profile of the live vaccine strain (LVS) of F. tularensis grown in the FL83B murine hepatocytic cell line compared to that of F. tularensis cultured in broth. The fslC gene of the fsl operon was the most highly upregulated. Deletion of fslC eliminated the ability of the LVS to produce siderophore, which is involved in uptake of ferric iron, but it did not impair its growth in hepatocytes, A549 epithelial cells, or macrophages. Therefore, we sought an alternative means by which F. tularensis might obtain iron. Deletion of feoB, which encodes a putative ferrous iron transporter, retarded replication of the LVS in iron-restricted media, reduced its growth in hepatocytic and epithelial cells, and impaired its acquisition of iron. Survival of mice infected intradermally with a lethal dose of the LVS was slightly improved by deletion of fslC but was not altered by loss of feoB. However, the ΔfeoB mutant showed diminished ability to colonize the lungs, liver, and spleen of mice that received sublethal inocula. Thus, FeoB represents a previously unidentified mechanism for uptake of iron by F. tularensis. Moreover, failure to produce a mutant strain lacking both feoB and fslC suggests that FeoB and the proteins of the fsl operon are the only major means by which F. tularensis acquires iron.
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Examination of in vitro epithelial cell lines as models for Francisella tularensis non-phagocytic infections. J Microbiol Methods 2013; 93:153-60. [DOI: 10.1016/j.mimet.2013.03.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2012] [Revised: 03/04/2013] [Accepted: 03/11/2013] [Indexed: 01/16/2023]
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45
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Identification of a live attenuated vaccine candidate for tularemia prophylaxis. PLoS One 2013; 8:e61539. [PMID: 23613871 PMCID: PMC3629233 DOI: 10.1371/journal.pone.0061539] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2012] [Accepted: 03/11/2013] [Indexed: 12/25/2022] Open
Abstract
Francisella tularensis is the causative agent of a fatal human disease, tularemia. F. tularensis was used in bioweapon programs in the past and is now classified as a category A select agent owing to its possible use in bioterror attacks. Despite over a century since its discovery, an effective vaccine is yet to be developed. In this study four transposon insertion mutants of F. tularensis live vaccine strain (LVS) in Na/H antiporter (FTL_0304), aromatic amino acid transporter (FTL_0291), outer membrane protein A (OmpA)-like family protein (FTL_0325) and a conserved hypothetical membrane protein gene (FTL_0057) were evaluated for their attenuation and protective efficacy against F. tularensis SchuS4 strain. All four mutants were 100–1000 fold attenuated for virulence in mice than parental F. tularensis. Except for the FTL_0304, single intranasal immunization with the other three mutants provided 100% protection in BALB/c mice against intranasal challenge with virulent F. tularensis SchuS4. Differences in the protective ability of the FTL_0325 and FTL_0304 mutant which failed to provide protection against SchuS4 were investigated further. The results indicated that an early pro-inflammatory response and persistence in host tissues established a protective immunity against F. tularensis SchuS4 in the FTL_0325 immunized mice. No differences were observed in the levels of serum IgG antibodies amongst the two vaccinated groups. Recall response studies demonstrated that splenocytes from the FTL_0325 mutant immunized mice induced significantly higher levels of IFN-γ and IL-17 cytokines than the FTL_0304 immunized counterparts indicating development of an effective memory response. Collectively, this study demonstrates that persistence of the vaccine strain together with its ability to induce an early pro-inflammatory innate immune response and strong memory responses can discriminate between successful and failed vaccinations against tularemia. This study describes a live attenuated vaccine which may prove to be an ideal vaccine candidate for prevention of respiratory tularemia.
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Celli J, Zahrt TC. Mechanisms of Francisella tularensis intracellular pathogenesis. Cold Spring Harb Perspect Med 2013; 3:a010314. [PMID: 23545572 DOI: 10.1101/cshperspect.a010314] [Citation(s) in RCA: 101] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Francisella tularensis is a zoonotic intracellular pathogen and the causative agent of the debilitating febrile illness tularemia. Although natural infections by F. tularensis are sporadic and generally localized, the low infectious dose, with the ability to be transmitted to humans via multiple routes and the potential to cause life-threatening infections, has led to concerns that this bacterium could be used as an agent of bioterror and released intentionally into the environment. Recent studies of F. tularensis and other closely related Francisella species have greatly increased our understanding of mechanisms used by this organism to infect and cause disease within the host. Here, we review the intracellular life cycle of Francisella and highlight key genetic determinants and/or pathways that contribute to the survival and proliferation of this bacterium within host cells.
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Affiliation(s)
- Jean Celli
- Laboratory of Intracellular Parasites, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, MO 59840, USA
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47
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Woolard MD, Barrigan LM, Fuller JR, Buntzman AS, Bryan J, Manoil C, Kawula TH, Frelinger JA. Identification of Francisella novicida mutants that fail to induce prostaglandin E(2) synthesis by infected macrophages. Front Microbiol 2013; 4:16. [PMID: 23403609 PMCID: PMC3568750 DOI: 10.3389/fmicb.2013.00016] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2012] [Accepted: 01/24/2013] [Indexed: 11/13/2022] Open
Abstract
Francisella tularensis is the causative agent of tularemia. We have previously shown that infection with F. tularensis Live Vaccine Strain (LVS) induces macrophages to synthesize prostaglandin E2 (PGE2). Synthesis of PGE2 by F. tularensis infected macrophages results in decreased T cell proliferation in vitro and increased bacterial survival in vivo. Although we understand some of the biological consequences of F. tularensis induced PGE2 synthesis by macrophages, we do not understand the cellular pathways (neither host nor bacterial) that result in up-regulation of the PGE2 biosynthetic pathway in F. tularensis infected macrophages. We took a genetic approach to begin to understand the molecular mechanisms of bacterial induction of PGE2 synthesis from infected macrophages. To identify F. tularensis genes necessary for the induction of PGE2 in primary macrophages, we infected cells with individual mutants from the closely related strain F. tularensis subspecies novicida U112 (U112) two allele mutant library. Twenty genes were identified that when disrupted resulted in U112 mutant strains unable to induce the synthesis of PGE2 by infected macrophages. Fourteen of the genes identified are located within the Francisella pathogenicity island (FPI). Genes in the FPI are required for F. tularensis to escape from the phagosome and replicate in the cytosol, which might account for the failure of U112 with transposon insertions within the FPI to induce PGE2. This implies that U112 mutant strains that do not grow intracellularly would also not induce PGE2. We found that U112 clpB::Tn grows within macrophages yet fails to induce PGE2, while U112 pdpA::Tn does not grow yet does induce PGE2. We also found that U112 iglC::Tn neither grows nor induces PGE2. These findings indicate that there is dissociation between intracellular growth and the ability of F. tularensis to induce PGE2 synthesis. These mutants provide a critical entrée into the pathways used in the host for PGE2 induction.
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Affiliation(s)
- Matthew D Woolard
- Department of Microbiology and Immunology, Louisiana State University Health Sciences Center at Shreveport Shreveport, LA, USA
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Tetratricopeptide repeat motifs in the world of bacterial pathogens: role in virulence mechanisms. Infect Immun 2012; 81:629-35. [PMID: 23264049 DOI: 10.1128/iai.01035-12] [Citation(s) in RCA: 118] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The tetratricopeptide repeat (TPR) structural motif is known to occur in a wide variety of proteins present in prokaryotic and eukaryotic organisms. The TPR motif represents an elegant module for the assembly of various multiprotein complexes, and thus, TPR-containing proteins often play roles in vital cell processes. As the TPR profile is well defined, the complete TPR protein repertoire of a bacterium with a known genomic sequence can be predicted. This provides a tremendous opportunity for investigators to identify new TPR-containing proteins and study them in detail. In the past decade, TPR-containing proteins of bacterial pathogens have been reported to be directly related to virulence-associated functions. In this minireview, we summarize the current knowledge of the TPR-containing proteins involved in virulence mechanisms of bacterial pathogens while highlighting the importance of TPR motifs for the proper functioning of class II chaperones of a type III secretion system in the pathogenesis of Yersinia, Pseudomonas, and Shigella.
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Production of outer membrane vesicles and outer membrane tubes by Francisella novicida. J Bacteriol 2012; 195:1120-32. [PMID: 23264574 DOI: 10.1128/jb.02007-12] [Citation(s) in RCA: 101] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Francisella spp. are highly infectious and virulent bacteria that cause the zoonotic disease tularemia. Knowledge is lacking for the virulence factors expressed by Francisella and how these factors are secreted and delivered to host cells. Gram-negative bacteria constitutively release outer membrane vesicles (OMV), which may function in the delivery of virulence factors to host cells. We identified growth conditions under which Francisella novicida produces abundant OMV. Purification of the vesicles revealed the presence of tube-shaped vesicles in addition to typical spherical OMV, and examination of whole bacteria revealed the presence of tubes extending out from the bacterial surface. Recently, both prokaryotic and eukaryotic cells have been shown to produce membrane-enclosed projections, termed nanotubes, which appear to function in cell-cell communication and the exchange of molecules. In contrast to these previously characterized structures, the F. novicida tubes are produced in liquid as well as on solid medium and are derived from the OM rather than the cytoplasmic membrane. The production of the OMV and tubes (OMV/T) by F. novicida was coordinately regulated and responsive to both growth medium and growth phase. Proteomic analysis of purified OMV/T identified known Francisella virulence factors among the constituent proteins, suggesting roles for the vesicles in pathogenesis. In support of this, production of OM tubes by F. novicida was stimulated during infection of macrophages and addition of purified OMV/T to macrophages elicited increased release of proinflammatory cytokines. Finally, vaccination with purified OMV/T protected mice from subsequent challenge with highly lethal doses of F. novicida.
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The Francisella tularensis FabI enoyl-acyl carrier protein reductase gene is essential to bacterial viability and is expressed during infection. J Bacteriol 2012; 195:351-8. [PMID: 23144254 DOI: 10.1128/jb.01957-12] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Francisella tularensis is classified as a category A priority pathogen and causes fatal disseminated disease in humans upon inhalation of less than 50 bacteria. Although drugs are available for treatment, they are not ideal because of toxicity and route of delivery, and in some cases patients relapse upon withdrawal. We have an ongoing program to develop novel FAS-II FabI enoyl-ACP reductase enzyme inhibitors for Francisella and other select agents. To establish F. tularensis FabI (FtFabI) as a clinically relevant drug target, we demonstrated that fatty acid biosynthesis and FabI activity are essential for growth even in the presence of exogenous long-chain lipids and that FtfabI is not transcriptionally altered in the presence of exogenous long-chain lipids. Inhibition of FtFabI or fatty acid synthesis results in loss of viability that is not rescued by exogenous long-chain lipid supplementation. Importantly, whole-genome transcriptional profiling of F. tularensis with DNA microarrays from infected tissues revealed that FtfabI and de novo fatty acid biosynthetic genes are transcriptionally active during infection. This is the first demonstration that the FabI enoyl-ACP-reductase enzyme encoded by F. tularensis is essential and not bypassed by exogenous fatty acids and that de novo fatty acid biosynthetic components encoded in F. tularensis are transcriptionally active during infection in the mouse model of tularemia.
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