1
|
Ahmad F, Javed K, Tahir A, Khan MUG, Abbas M, Rabbani M, Shabbir MZ. Identifying key soil characteristics for Francisella tularensis classification with optimized Machine learning models. Sci Rep 2024; 14:1743. [PMID: 38242908 PMCID: PMC10799052 DOI: 10.1038/s41598-024-51502-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2023] [Accepted: 01/05/2024] [Indexed: 01/21/2024] Open
Abstract
Francisella tularensis (Ft) poses a significant threat to both animal and human populations, given its potential as a bioweapon. Current research on the classification of this pathogen and its relationship with soil physical-chemical characteristics often relies on traditional statistical methods. In this study, we leverage advanced machine learning models to enhance the prediction of epidemiological models for soil-based microbes. Our model employs a two-stage feature ranking process to identify crucial soil attributes and hyperparameter optimization for accurate pathogen classification using a unique soil attribute dataset. Optimization involves various classification algorithms, including Support Vector Machines (SVM), Ensemble Models (EM), and Neural Networks (NN), utilizing Bayesian and Random search techniques. Results indicate the significance of soil features such as clay, nitrogen, soluble salts, silt, organic matter, and zinc , while identifying the least significant ones as potassium, calcium, copper, sodium, iron, and phosphorus. Bayesian optimization yields the best results, achieving an accuracy of 86.5% for SVM, 81.8% for EM, and 83.8% for NN. Notably, SVM emerges as the top-performing classifier, with an accuracy of 86.5% for both Bayesian and Random Search optimizations. The insights gained from employing machine learning techniques enhance our understanding of the environmental factors influencing Ft's persistence in soil. This, in turn, reduces the risk of false classifications, contributing to better pandemic control and mitigating socio-economic impacts on communities.
Collapse
Affiliation(s)
- Fareed Ahmad
- Department of Computer Science, University of Engineering and Technology, Lahore, Pakistan.
- Quality Operations Laboratory, Institute of Microbiology, University of Veterinary and Animal Sciences, Lahore, Pakistan.
| | - Kashif Javed
- Department of Electrical Engineering, University of Engineering and Technology, Lahore, Pakistan
| | - Ahsen Tahir
- Department of Electrical Engineering, University of Engineering and Technology, Lahore, Pakistan
| | | | - Mateen Abbas
- Quality Operations Laboratory, Institute of Microbiology, University of Veterinary and Animal Sciences, Lahore, Pakistan
| | - Masood Rabbani
- Institute of Microbiology, University of Veterinary and Animal Sciences, Lahore, Pakistan
| | - Muhammad Zubair Shabbir
- Quality Operations Laboratory, Institute of Microbiology, University of Veterinary and Animal Sciences, Lahore, Pakistan
| |
Collapse
|
2
|
Degabriel M, Valeva S, Boisset S, Henry T. Pathogenicity and virulence of Francisella tularensis. Virulence 2023; 14:2274638. [PMID: 37941380 PMCID: PMC10653695 DOI: 10.1080/21505594.2023.2274638] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2023] [Accepted: 10/18/2023] [Indexed: 11/10/2023] Open
Abstract
Tularaemia is a zoonotic disease caused by the Gram-negative bacterium, Francisella tularensis. Depending on its entry route into the organism, F. tularensis causes different diseases, ranging from life-threatening pneumonia to less severe ulceroglandular tularaemia. Various strains with different geographical distributions exhibit different levels of virulence. F. tularensis is an intracellular bacterium that replicates primarily in the cytosol of the phagocytes. The main virulence attribute of F. tularensis is the type 6 secretion system (T6SS) and its effectors that promote escape from the phagosome. In addition, F. tularensis has evolved a peculiar envelope that allows it to escape detection by the immune system. In this review, we cover tularaemia, different Francisella strains, and their pathogenicity. We particularly emphasize the intracellular life cycle, associated virulence factors, and metabolic adaptations. Finally, we present how F. tularensis largely escapes immune detection to be one of the most infectious and lethal bacterial pathogens.
Collapse
Affiliation(s)
- Manon Degabriel
- CIRI, Centre International de Recherche en Infectiologie, Inserm U1111, Université Claude Bernard Lyon 1, CNRS, UMR5308, ENS de Lyon, Univ Lyon, LYON, France
| | - Stanimira Valeva
- CIRI, Centre International de Recherche en Infectiologie, Inserm U1111, Université Claude Bernard Lyon 1, CNRS, UMR5308, ENS de Lyon, Univ Lyon, LYON, France
| | - Sandrine Boisset
- CIRI, Centre International de Recherche en Infectiologie, Inserm U1111, Université Claude Bernard Lyon 1, CNRS, UMR5308, ENS de Lyon, Univ Lyon, LYON, France
- Univ. Grenoble Alpes, CHU Grenoble Alpes, CNRS, CEA, UMR5075, Institut de Biologie Structurale, Grenoble, France
| | - Thomas Henry
- CIRI, Centre International de Recherche en Infectiologie, Inserm U1111, Université Claude Bernard Lyon 1, CNRS, UMR5308, ENS de Lyon, Univ Lyon, LYON, France
| |
Collapse
|
3
|
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.
Collapse
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
| |
Collapse
|
4
|
Ahmad F, Farooq A, Ghani Khan MU, Shabbir MZ, Rabbani M, Hussain I. Identification of Most Relevant Features for Classification of Francisella tularensis using Machine Learning. Curr Bioinform 2021. [DOI: 10.2174/1574893615666200219113900] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Background:
Francisella tularensis is a stealth pathogen fatal for animals and humans.
Ease of its propagation, coupled with high capacity for ailment and death makes it a potential
candidate for biological weapon.
Objective:
Work related to the pathogen’s classification and factors affecting its prolonged
existence in soil is limited to statistical measures. Machine learning other than conventional
analysis methods may be applied to better predict epidemiological modeling for this soil-borne
pathogen.
Methods:
Feature-ranking algorithms namely; relief, correlation and oneR are used for soil
attribute ranking. Moreover, classification algorithms; SVM, random forest, naive bayes, logistic
regression and MLP are used for classification of the soil attribute dataset for Francisella
tularensis positive and negative soils.
Results:
Feature-ranking methods concluded that clay, nitrogen, organic matter, soluble salts, zinc,
silt and nickel are the most significant attributes while potassium, phosphorous, iron, calcium,
copper, chromium and sand are the least contributing risk factors for the persistence of the
pathogen. However, clay is the most significant and potassium is the least contributing attribute.
Data analysis suggests that feature-ranking using relief produced classification accuracy of 84.35%
for multilayer perceptron; 82.99% for linear regression; 80.27% for SVM and random forest; and
78.23% for naive bayes, which is better than other ranking methods. MLP outperforms other
classifiers by generating an accuracy of 84.35%, 82.99% and 81.63% for feature-ranking using
relief, correlation and oneR algorithms, respectively.
Conclusion:
These models can significantly improve accuracy and can minimize the risk of
incorrect classification. They further help in controlling epidemics and thereby minimizing the
socio-economic impact on the society.
Collapse
Affiliation(s)
- Fareed Ahmad
- Department of Computer Science and Engineering, Faculty of Electrical Engineering, University of Engineering and Technology, Lahore, Pakistan
| | - Amjad Farooq
- Department of Computer Science and Engineering, Faculty of Electrical Engineering, University of Engineering and Technology, Lahore, Pakistan
| | - Muhammad Usman Ghani Khan
- Department of Computer Science and Engineering, Faculty of Electrical Engineering, University of Engineering and Technology, Lahore, Pakistan
| | | | - Masood Rabbani
- Institute of Microbiology, University of Veterinary and Animal Sciences, Lahore, Pakistan
| | - Irshad Hussain
- Institute of Microbiology, University of Veterinary and Animal Sciences, Lahore, Pakistan
| |
Collapse
|
5
|
Brodmann M, Heilig R, Broz P, Basler M. Mobilizable Plasmids for Tunable Gene Expression in Francisella novicida. Front Cell Infect Microbiol 2018; 8:284. [PMID: 30234022 PMCID: PMC6128221 DOI: 10.3389/fcimb.2018.00284] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2018] [Accepted: 07/25/2018] [Indexed: 01/02/2023] Open
Abstract
Francisella tularensis is the causative agent of the life-threatening disease tularemia. However, the molecular tools to study Francisella are limited. Especially, expression plasmids are sparse and difficult to use, as they are unstable and prone to spontaneous loss. Most Francisella expression plasmids lack inducible promoters making it difficult to control gene expression levels. In addition, available expression plasmids are mainly designed for F. tularensis, however, genetic differences including restriction-modification systems impede the use of these plasmids in F. novicida, which is often used as a model organism to study Francisella pathogenesis. Here we report construction and characterization of two mobilizable plasmids (pFNMB1 and pFNMB2) designed for regulated gene expression in F. novicida. pFNMB plasmids contain a tetracycline inducible promoter to control gene expression levels and oriT for RP4 mediated mobilization. We show that both plasmids are stably maintained in bacteria for more than 40 generations over 4 days of culturing in the absence of selection against plasmid loss. Expression levels are dependent on anhydrotetracycline concentration and homogeneous in a bacterial population. pFNMB1 and pFNMB2 plasmids differ in the sequence between promoter and translation start site and thus allow to reach different maximum levels of protein expression. We used pFNMB1 and pFNMB2 for complementation of Francisella Pathogenicity Island mutants ΔiglF, ΔiglI, and ΔiglC in-vitro and pFNMB1 to complement ΔiglI mutant in bone marrow derived macrophages.
Collapse
Affiliation(s)
- Maj Brodmann
- Biozentrum, University of Basel, Basel, Switzerland
| | - Rosalie Heilig
- Department of Biochemistry, University of Lausanne, Épalinges, Switzerland
| | - Petr Broz
- Department of Biochemistry, University of Lausanne, Épalinges, Switzerland
| | - Marek Basler
- Biozentrum, University of Basel, Basel, Switzerland
| |
Collapse
|
6
|
Abstract
Francisella tularensis is the causative agent of the potentially lethal disease tularemia. Due to a low infectious dose and ease of airborne transmission, Francisella is classified as a category A biological agent. Despite the possible risk to public health, there is no safe and fully licensed vaccine. A potential vaccine candidate, an attenuated live vaccine strain, does not fulfil the criteria for general use. In this review, we will summarize existing and new candidates for live attenuated and subunit vaccines.
Collapse
|
7
|
Wallqvist A, Memišević V, Zavaljevski N, Pieper R, Rajagopala SV, Kwon K, Yu C, Hoover TA, Reifman J. Using host-pathogen protein interactions to identify and characterize Francisella tularensis virulence factors. BMC Genomics 2015; 16:1106. [PMID: 26714771 PMCID: PMC4696196 DOI: 10.1186/s12864-015-2351-1] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2015] [Accepted: 12/21/2015] [Indexed: 11/10/2022] Open
Abstract
Background Francisella tularensis is a select bio-threat agent and one of the most virulent intracellular pathogens known, requiring just a few organisms to establish an infection. Although several virulence factors are known, we lack an understanding of virulence factors that act through host-pathogen protein interactions to promote infection. To address these issues in the highly infectious F. tularensis subsp. tularensis Schu S4 strain, we deployed a combined in silico, in vitro, and in vivo analysis to identify virulence factors and their interactions with host proteins to characterize bacterial infection mechanisms. Results We initially used comparative genomics and literature to identify and select a set of 49 putative and known virulence factors for analysis. Each protein was then subjected to proteome-scale yeast two-hybrid (Y2H) screens with human and murine cDNA libraries to identify potential host-pathogen protein-protein interactions. Based on the bacterial protein interaction profile with both hosts, we selected seven novel putative virulence factors for mutant construction and animal validation experiments. We were able to create five transposon insertion mutants and used them in an intranasal BALB/c mouse challenge model to establish 50 % lethal dose estimates. Three of these, ΔFTT0482c, ΔFTT1538c, and ΔFTT1597, showed attenuation in lethality and can thus be considered novel F. tularensis virulence factors. The analysis of the accompanying Y2H data identified intracellular protein trafficking between the early endosome to the late endosome as an important component in virulence attenuation for these virulence factors. Furthermore, we also used the Y2H data to investigate host protein binding of two known virulence factors, showing that direct protein binding was a component in the modulation of the inflammatory response via activation of mitogen-activated protein kinases and in the oxidative stress response. Conclusions Direct interactions with specific host proteins and the ability to influence interactions among host proteins are important components for F. tularensis to avoid host-cell defense mechanisms and successfully establish an infection. Although direct host-pathogen protein-protein binding is only one aspect of Francisella virulence, it is a critical component in directly manipulating and interfering with cellular processes in the host cell. Electronic supplementary material The online version of this article (doi:10.1186/s12864-015-2351-1) contains supplementary material, which is available to authorized users.
Collapse
Affiliation(s)
- Anders Wallqvist
- Department of Defense Biotechnology High Performance Computing Software Applications Institute, Telemedicine and Advanced Technology Research Center, U.S. Army Medical Research and Materiel Command, Fort Detrick, MD, 21702, USA.
| | - Vesna Memišević
- Department of Defense Biotechnology High Performance Computing Software Applications Institute, Telemedicine and Advanced Technology Research Center, U.S. Army Medical Research and Materiel Command, Fort Detrick, MD, 21702, USA.
| | - Nela Zavaljevski
- Department of Defense Biotechnology High Performance Computing Software Applications Institute, Telemedicine and Advanced Technology Research Center, U.S. Army Medical Research and Materiel Command, Fort Detrick, MD, 21702, USA.
| | | | | | - Keehwan Kwon
- J. Craig Venter Institute, Rockville, MD, 20850, USA.
| | - Chenggang Yu
- Department of Defense Biotechnology High Performance Computing Software Applications Institute, Telemedicine and Advanced Technology Research Center, U.S. Army Medical Research and Materiel Command, Fort Detrick, MD, 21702, USA.
| | - Timothy A Hoover
- Bacteriology Division, U.S. Army Medical Research Institute of Infectious Diseases, Fort Detrick, MD, 21702, USA.
| | - Jaques Reifman
- Department of Defense Biotechnology High Performance Computing Software Applications Institute, Telemedicine and Advanced Technology Research Center, U.S. Army Medical Research and Materiel Command, Fort Detrick, MD, 21702, USA.
| |
Collapse
|
8
|
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.
Collapse
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
| |
Collapse
|
9
|
Abstract
Type IV pili (T4P) are multifunctional protein fibers produced on the surfaces of a wide variety of bacteria and archaea. The major subunit of T4P is the type IV pilin, and structurally related proteins are found as components of the type II secretion (T2S) system, where they are called pseudopilins; of DNA uptake/competence systems in both Gram-negative and Gram-positive species; and of flagella, pili, and sugar-binding systems in the archaea. This broad distribution of a single protein family implies both a common evolutionary origin and a highly adaptable functional plan. The type IV pilin is a remarkably versatile architectural module that has been adopted widely for a variety of functions, including motility, attachment to chemically diverse surfaces, electrical conductance, acquisition of DNA, and secretion of a broad range of structurally distinct protein substrates. In this review, we consider recent advances in this research area, from structural revelations to insights into diversity, posttranslational modifications, regulation, and function.
Collapse
|
10
|
Abstract
Our understanding of the virulence and pathogenesis of Francisella spp. has significantly advanced in recent years, including a new understanding that this organism can form biofilms. What is known so far about Francisella spp. biofilms is summarized here and future research questions are suggested. The molecular basis of biofilm production has begun to be studied, especially the role of extracellular carbohydrates and capsule, quorum sensing and two-component signaling systems. Further work has explored the contribution of amoebae, pili, outer-membrane vesicles, chitinases, and small molecules such as c-di-GMP to Francisella spp. biofilm formation. A role for Francisella spp. biofilm in feeding mosquito larvae has been suggested. As no strong role in virulence has been found yet, Francisella spp. biofilm formation is most likely a key mechanism for environmental survival and persistence. The significance and importance of Francisella spp.’s biofilm phenotype as a critical aspect of its microbial physiology is being developed. Areas for further studies include the potential role of Francisella spp. biofilms in the infection of mammalian hosts and virulence regulation.
Collapse
Affiliation(s)
- Monique L van Hoek
- School of Systems Biology and National Center for Biodefense and Infectious Diseases; George Mason University; Manassas, VA USA
| |
Collapse
|
11
|
Abstract
Francisella tularensis is a highly virulent bacterial pathogen that is easily aerosolized and has a low infectious dose. As an intracellular pathogen, entry of Francisella into host cells is critical for its survival and virulence. However, the initial steps of attachment and internalization of Francisella into host cells are not well characterized, and little is known about bacterial factors that promote these processes. This review highlights our current understanding of Francisella attachment and internalization into host cells. In particular, we emphasize the host cell types Francisella has been shown to interact with, as well as specific receptors and signaling processes involved in the internalization process. This review will shed light on gaps in our current understanding and future areas of investigation.
Collapse
Affiliation(s)
- G Brett Moreau
- Department of Microbiology, Immunology, and Cancer Biology; University of Virginia; Charlottesville, VA USA
| | - Barbara J Mann
- Department of Microbiology, Immunology, and Cancer Biology; University of Virginia; Charlottesville, VA USA; Department of Medicine; Division of Infectious Diseases and International Health; University of Virginia; Charlottesville, VA USA
| |
Collapse
|
12
|
Ramond E, Gesbert G, Barel M, Charbit A. Proteins involved in Francisella tularensis survival and replication inside macrophages. Future Microbiol 2013; 7:1255-68. [PMID: 23075445 DOI: 10.2217/fmb.12.103] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Francisella tularensis, the etiological agent of tularemia, is a member of the γ-proteobacteria class of Gram-negative bacteria. This highly virulent bacterium can infect a large range of mammalian species and has been recognized as a human pathogen for a century. F. tularensis is able to survive in vitro in a variety of cell types. In vivo, the bacterium replicates mainly in infected macrophages, using the cytoplasmic compartment as a replicative niche. To successfully adapt to this stressful environment, F. tularensis must simultaneously: produce and regulate the expression of a series of dedicated virulence factors; adapt its metabolic needs to the nutritional context of the host cytosol; and control the innate immune cytosolic surveillance pathways to avoid premature cell death. We will focus here on the secretion or release of bacterial proteins in the host, as well as on the envelope proteins, involved in bacterial survival inside macrophages.
Collapse
Affiliation(s)
- Elodie Ramond
- Faculté de Médecine Necker, Université Paris Descartes, 156 Rue de Vaugirard, 75730 Paris, Cedex 15, France
| | | | | | | |
Collapse
|
13
|
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.
Collapse
|
14
|
Hartung S, Arvai AS, Wood T, Kolappan S, Shin DS, Craig L, Tainer JA. Ultrahigh resolution and full-length pilin structures with insights for filament assembly, pathogenic functions, and vaccine potential. J Biol Chem 2011; 286:44254-44265. [PMID: 22027840 PMCID: PMC3243539 DOI: 10.1074/jbc.m111.297242] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2011] [Revised: 10/10/2011] [Indexed: 11/06/2022] Open
Abstract
Pilin proteins assemble into Type IV pili (T4P), surface-displayed bacterial filaments with virulence functions including motility, attachment, transformation, immune escape, and colony formation. However, challenges in crystallizing full-length fiber-forming and membrane protein pilins leave unanswered questions regarding pilin structures, assembly, functions, and vaccine potential. Here we report pilin structures of full-length DnFimA from the sheep pathogen Dichelobacter nodosus and FtPilE from the human pathogen Francisella tularensis at 2.3 and 1 Å resolution, respectively. The DnFimA structure reveals an extended kinked N-terminal α-helix, an unusual centrally located disulfide, conserved subdomains, and assembled epitopes informing serogroup vaccines. An interaction between the conserved Glu-5 carboxyl oxygen and the N-terminal amine of an adjacent subunit in the crystallographic dimer is consistent with the hypothesis of a salt bridge between these groups driving T4P assembly. The FtPilE structure identifies an authentic Type IV pilin and provides a framework for understanding the role of T4P in F. tularensis virulence. Combined results define a unified pilin architecture, specialized subdomain roles in pilus assembly and function, and potential therapeutic targets.
Collapse
Affiliation(s)
- Sophia Hartung
- Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720
| | - Andrew S Arvai
- Department of Molecular Biology and the Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, California 92037
| | - Timothy Wood
- Department of Molecular Biology and the Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, California 92037
| | - Subramaniapillai Kolappan
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada
| | - David S Shin
- Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720
| | - Lisa Craig
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada.
| | - John A Tainer
- Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720; Department of Molecular Biology and the Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, California 92037.
| |
Collapse
|
15
|
Ireland PM, LeButt H, Thomas RM, Oyston PCF. A Francisella tularensis SCHU S4 mutant deficient in γ-glutamyltransferase activity induces protective immunity: characterization of an attenuated vaccine candidate. MICROBIOLOGY-SGM 2011; 157:3172-3179. [PMID: 21852349 DOI: 10.1099/mic.0.052902-0] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Francisella tularensis is an intracellular pathogen which causes tularaemia. There is no licensed vaccine currently available for prophylaxis. The γ-glutamyl transpeptidase (GGT) encoded by the ggt gene has been shown to be important for the intracellular survival of F. tularensis. In this study we have constructed a ggt deletion mutant in the highly virulent F. tularensis strain SCHU S4. Characterization of the mutant strain confirmed the function of ggt, and confirmed the role of GGT in cysteine acquisition. The mutant strain was highly attenuated both in vitro and in vivo using murine models of infection. Moreover, we have demonstrated that the attenuated mutant is able to induce protective immunity against an F. tularensis SCHU S4 challenge, and thus may be a candidate for the development of an attenuated vaccine.
Collapse
Affiliation(s)
- Philip M Ireland
- Defence Science and Technology Laboratory, Porton Down, Salisbury, Wiltshire SP4 0JQ, UK
| | - Helen LeButt
- Defence Science and Technology Laboratory, Porton Down, Salisbury, Wiltshire SP4 0JQ, UK
| | - Rebecca M Thomas
- Defence Science and Technology Laboratory, Porton Down, Salisbury, Wiltshire SP4 0JQ, UK
| | - Petra C F Oyston
- Defence Science and Technology Laboratory, Porton Down, Salisbury, Wiltshire SP4 0JQ, UK
| |
Collapse
|