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Diamant I, Adani B, Sylman M, Rahav G, Gal-Mor O. The transcriptional regulation of the horizontally acquired iron uptake system, yersiniabactin and its contribution to oxidative stress tolerance and pathogenicity of globally emerging salmonella strains. Gut Microbes 2024; 16:2369339. [PMID: 38962965 PMCID: PMC11225919 DOI: 10.1080/19490976.2024.2369339] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/09/2024] [Accepted: 06/12/2024] [Indexed: 07/05/2024] Open
Abstract
The bacterial species Salmonella enterica (S. enterica) is a highly diverse pathogen containing more than 2600 distinct serovars, which can infect a wide range of animal and human hosts. Recent global emergence of multidrug resistant strains, from serovars Infantis and Muenchen is associated with acquisition of the epidemic megaplasmid, pESI that augments antimicrobial resistance and pathogenicity. One of the main pESI's virulence factors is the potent iron uptake system, yersiniabactin encoded by fyuA, irp2-irp1-ybtUTE, ybtA, and ybtPQXS gene cluster. Here we show that yersiniabactin, has an underappreciated distribution among different S. enterica serovars and subspecies, integrated in their chromosome or carried by different conjugative plasmids, including pESI. While the genetic organization and the coding sequence of the yersiniabactin genes are generally conserved, a 201-bp insertion sequence upstream to ybtA, was identified in pESI. Despite this insertion, pESI-encoded yersiniabactin is regulated by YbtA and the ancestral Ferric Uptake Regulator (Fur), which binds directly to the ybtA and irp2 promoters. Furthermore, we show that yersiniabactin genes are specifically induced during the mid-late logarithmic growth phase and in response to iron-starvation or hydrogen peroxide. Concurring, yersiniabactin was found to play a previously unknown role in oxidative stress tolerance and to enhance intestinal colonization of S. Infantis in mice. These results indicate that yersiniabactin contributes to Salmonella fitness and pathogenicity in vivo and is likely to play a role in the rapid dissemination of pESI among globally emerging Salmonella lineages.
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Affiliation(s)
- Imbar Diamant
- The Infectious Diseases Research Laboratory, Sheba Medical Center, Tel-Hashomer, Israel
- Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Boaz Adani
- The Infectious Diseases Research Laboratory, Sheba Medical Center, Tel-Hashomer, Israel
| | - Meir Sylman
- The Infectious Diseases Research Laboratory, Sheba Medical Center, Tel-Hashomer, Israel
| | - Galia Rahav
- The Infectious Diseases Research Laboratory, Sheba Medical Center, Tel-Hashomer, Israel
- Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Ohad Gal-Mor
- The Infectious Diseases Research Laboratory, Sheba Medical Center, Tel-Hashomer, Israel
- Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
- Department of Clinical Microbiology and Immunology, Tel Aviv University, Tel Aviv, Israel
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2
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Chee WKD, Yeoh JW, Dao VL, Poh CL. Highly Reversible Tunable Thermal-Repressible Split-T7 RNA Polymerases (Thermal-T7RNAPs) for Dynamic Gene Regulation. ACS Synth Biol 2022; 11:921-937. [PMID: 35089710 DOI: 10.1021/acssynbio.1c00545] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Temperature is a physical cue that is easy to apply, allowing cellular behaviors to be controlled in a contactless and dynamic manner via heat-inducible/repressible systems. However, existing heat-repressible systems are limited in number, rely on thermal sensitive mRNA or transcription factors that function at low temperatures, lack tunability, suffer delays, and are overly complex. To provide an alternative mode of thermal regulation, we developed a library of compact, reversible, and tunable thermal-repressible split-T7 RNA polymerase systems (Thermal-T7RNAPs), which fused temperature-sensitive domains of Tlpa protein with split-T7RNAP to enable direct thermal control of the T7RNAP activity between 30 and 42 °C. We generated a large mutant library with varying thermal performances via an automated screening framework to extend temperature tunability. Lastly, using the mutants, novel thermal logic circuitry was implemented to regulate cell growth and achieve active thermal control of the cell proportions within co-cultures. Overall, this technology expanded avenues for thermal control in biotechnology applications.
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Affiliation(s)
- Wai Kit David Chee
- Department of Biomedical Engineering, College of Design and Engineering, National University of Singapore, 4 Engineering Drive 3, 117583 Singapore
- NUS Synthetic Biology for Clinical and Technological Innovation (SynCTI), National University of Singapore, 28 Medical Drive, 117456 Singapore
| | - Jing Wui Yeoh
- Department of Biomedical Engineering, College of Design and Engineering, National University of Singapore, 4 Engineering Drive 3, 117583 Singapore
- NUS Synthetic Biology for Clinical and Technological Innovation (SynCTI), National University of Singapore, 28 Medical Drive, 117456 Singapore
| | - Viet Linh Dao
- Department of Biomedical Engineering, College of Design and Engineering, National University of Singapore, 4 Engineering Drive 3, 117583 Singapore
- NUS Synthetic Biology for Clinical and Technological Innovation (SynCTI), National University of Singapore, 28 Medical Drive, 117456 Singapore
| | - Chueh Loo Poh
- Department of Biomedical Engineering, College of Design and Engineering, National University of Singapore, 4 Engineering Drive 3, 117583 Singapore
- NUS Synthetic Biology for Clinical and Technological Innovation (SynCTI), National University of Singapore, 28 Medical Drive, 117456 Singapore
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3
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Cohen E, Azriel S, Auster O, Gal A, Zitronblat C, Mikhlin S, Scharte F, Hensel M, Rahav G, Gal-Mor O. Pathoadaptation of the passerine-associated Salmonella enterica serovar Typhimurium lineage to the avian host. PLoS Pathog 2021; 17:e1009451. [PMID: 33739988 PMCID: PMC8011750 DOI: 10.1371/journal.ppat.1009451] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2020] [Revised: 03/31/2021] [Accepted: 03/04/2021] [Indexed: 12/15/2022] Open
Abstract
Salmonella enterica is a diverse bacterial pathogen and a primary cause of human and animal infections. While many S. enterica serovars present a broad host-specificity, several specialized pathotypes have been adapted to colonize and cause disease in one or limited numbers of host species. The underlying mechanisms defining Salmonella host-specificity are far from understood. Here, we present genetic analysis, phenotypic characterization and virulence profiling of a monophasic S. enterica serovar Typhimurium strain that was isolated from several wild sparrows in Israel. Whole genome sequencing and complete assembly of its genome demonstrate a unique genetic signature that includes the integration of the BTP1 prophage, loss of the virulence plasmid, pSLT and pseudogene accumulation in multiple T3SS-2 effectors (sseJ, steC, gogB, sseK2, and sseK3), catalase (katE), tetrathionate respiration (ttrB) and several adhesion/ colonization factors (lpfD, fimH, bigA, ratB, siiC and siiE) encoded genes. Correspondingly, this strain demonstrates impaired biofilm formation, intolerance to oxidative stress and compromised intracellular replication within non-phagocytic host cells. Moreover, while this strain showed attenuated pathogenicity in the mouse, it was highly virulent and caused an inflammatory disease in an avian host. Overall, our findings demonstrate a unique phenotypic profile and genetic makeup of an overlooked S. Typhimurium sparrow-associated lineage and present distinct genetic signatures that are likely to contribute to its pathoadaptation to passerine birds. During Salmonella enterica evolution, many different ecological niches have been effectively occupied by this highly diverse bacterial pathogen. While many S. enterica serovars successfully maintained their ability to infect and colonize in a wide-array of host species, a few biotypes have evolved to colonize and cause a disease in only one or a small group of hosts. The evolutionary dynamic and the mechanisms shaping the host-specificity of Salmonella adapted strains are important to better understand Salmonella pathogenicity and its ecology, but still not fully understood. Here, we report genetic and phenotypic characterization of a S. Typhimurium strain that was isolated from several wild sparrows in Israel. This strain presented unique phenotypic profile that included impaired biofilm formation, high sensitivity to oxidative stress and reduced intracellular replication in non-phagocytic cells. In addition, while this strain was able to cause high inflammatory disease in an avian host, it was highly attenuated in the mouse model. Genome analysis identified that specific genetic signatures found in the sparrow strain are more frequently associated with poultry isolates than clinical isolates of S. Typhimurium. These genetic features are expected to accumulatively contribute toward the adaptation of this strain to birds.
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Affiliation(s)
- Emiliano Cohen
- The Infectious Diseases Research Laboratory, Sheba Medical Center, Tel-Hashomer, Israel
| | - Shalevet Azriel
- The Infectious Diseases Research Laboratory, Sheba Medical Center, Tel-Hashomer, Israel
| | - Oren Auster
- The Infectious Diseases Research Laboratory, Sheba Medical Center, Tel-Hashomer, Israel
- Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
- Department of Clinical Microbiology and Immunology, Tel Aviv University, Tel Aviv, Israel
| | - Adiv Gal
- Faculty of Sciences, Kibbutzim College, Tel-Aviv Israel
| | | | | | - Felix Scharte
- Abteilung Mikrobiologie, Universität Osnabrück, Osnabrück, Germany
| | - Michael Hensel
- Abteilung Mikrobiologie, Universität Osnabrück, Osnabrück, Germany
| | - Galia Rahav
- The Infectious Diseases Research Laboratory, Sheba Medical Center, Tel-Hashomer, Israel
- Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Ohad Gal-Mor
- The Infectious Diseases Research Laboratory, Sheba Medical Center, Tel-Hashomer, Israel
- Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
- Department of Clinical Microbiology and Immunology, Tel Aviv University, Tel Aviv, Israel
- * E-mail:
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Mandin P, Johansson J. Feeling the heat at the millennium: Thermosensors playing with fire. Mol Microbiol 2020; 113:588-592. [PMID: 31971637 DOI: 10.1111/mmi.14468] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2019] [Revised: 01/16/2020] [Accepted: 01/17/2020] [Indexed: 12/01/2022]
Abstract
An outstanding question regards the ability of organisms to sense their environments and respond in a suitable way. Pathogenic bacteria in particular exploit host-temperature sensing as a cue for triggering virulence gene expression. This micro-review does not attempt to fully cover the field of bacterial thermosensors and in detail describe each identified case. Instead, the review focus on the time-period at the end of the 1990's and beginning of the 2000's when several key discoveries were made, identifying protein, DNA and RNA as potential thermosensors controlling gene expression in several different bacterial pathogens in general and on the prfA thermosensor of Listeria monocytogenes in particular.
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Affiliation(s)
- Pierre Mandin
- Aix Marseille Univ-CNRS, UMR 7243, Laboratoire de Chimie Bactérienne, Institut de Microbiologie de la Méditerranée, Marseille, France
| | - Jörgen Johansson
- Department of Molecular Biology, Umeå University, Umeå, Sweden.,Molecular Infection Medicine, Sweden (MIMS), Umeå University, Umeå, Sweden.,Umeå Centre for Microbial Research, Umeå University, Umeå, Sweden
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5
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A folding reaction at the C-terminal domain drives temperature sensing in TRPM8 channels. Proc Natl Acad Sci U S A 2020; 117:20298-20304. [PMID: 32747539 DOI: 10.1073/pnas.2004303117] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
In mammals, temperature-sensitive TRP channels make membrane conductance of cells extremely temperature dependent, allowing the detection of temperature ranging from noxious cold to noxious heat. We progressively deleted the distal carboxyl terminus domain (CTD) of the cold-activated melastatin receptor channel, TRPM8. We found that the enthalpy change associated with channel gating is proportional to the length of the CTD. Deletion of the last 36 amino acids of the CTD transforms TRPM8 into a reduced temperature-sensitivity channel (Q10 ∼4). Exposing the intracellular domain to a denaturing agent increases the energy required to open the channel indicating that cold drives channel gating by stabilizing the folded state of the CTD. Experiments in the presence of an osmoticant agent suggest that channel gating involves a change in solute-inaccessible volume in the CTD of ∼1,900 Å3 This volume matches the void space inside the coiled coil according to the cryogenic electron microscopy structure of TRPM8. The results indicate that a folding-unfolding reaction of a specialized temperature-sensitive structure is coupled to TRPM8 gating.
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Aviv G, Cornelius A, Davidovich M, Cohen H, Suwandi A, Galeev A, Steck N, Azriel S, Rokney A, Valinsky L, Rahav G, Grassl GA, Gal-Mor O. Differences in the expression of SPI-1 genes pathogenicity and epidemiology between the emerging Salmonella enterica serovar Infantis and the model Salmonella enterica serovar Typhimurium. J Infect Dis 2020; 220:1071-1081. [PMID: 31062854 DOI: 10.1093/infdis/jiz235] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2018] [Accepted: 05/06/2019] [Indexed: 01/21/2023] Open
Abstract
BACKGROUND Salmonella enterica serovar Infantis (S. Infantis) is one of the ubiquitous serovars of the bacterial pathogen S. enterica and recently has been emerging in many countries worldwide. Nonetheless, not much is known about its epidemiology, host adaptation, and virulence. METHODS Epidemiological and molecular approaches were used together with tissue-culture and mouse models to conduct phenotypic comparison with the model S. enterica serovar Typhimurium. RESULTS We show that S. Infantis is more frequently associated with infections in infants <2 years old and prone to cause significantly less invasive infections than serovar Typhimurium. Moreover, although S. Infantis adheres better to host cells and highly colonizes mouse intestines soon after infection, it is significantly less invasive and induces much lower inflammation and disease in vivo than S. Typhimurium. These differences were associated with lower expression of Salmonella pathogenicity island (SPI) 1 genes in S. Infantis than in S. Typhimurium. CONCLUSIONS Our results demonstrate previously unknown differences in the epidemiology, virulence pathway expression, and pathogenicity between two highly abundant Salmonella serovars and suggest that native variation in the expression of the SPI-1 regulon is likely to contribute to epidemiological and virulence variation between genetically similar nontyphoidal Salmonella serovars.
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Affiliation(s)
- Gili Aviv
- The Infectious Diseases Research Laboratory, Sheba Medical Center, Tel-Hashomer.,Department of Clinical Microbiology and Immunology, Jerusalem, Israel.,Sackler Faculty of Medicine, Tel Aviv University, Jerusalem, Israel
| | | | | | - Helit Cohen
- The Infectious Diseases Research Laboratory, Sheba Medical Center, Tel-Hashomer
| | - Abdulhadi Suwandi
- Institute for Medical Microbiology and Hospital Epidemiology, Hannover Medical School and German Center for Infection Research, Partner Site Hannover-Braunschweig
| | - Alibek Galeev
- Institute for Medical Microbiology and Hospital Epidemiology, Hannover Medical School and German Center for Infection Research, Partner Site Hannover-Braunschweig
| | | | - Shalhevet Azriel
- The Infectious Diseases Research Laboratory, Sheba Medical Center, Tel-Hashomer
| | - Assaf Rokney
- Central Laboratories, Ministry of Health, Jerusalem, Israel
| | - Lea Valinsky
- Central Laboratories, Ministry of Health, Jerusalem, Israel
| | - Galia Rahav
- The Infectious Diseases Research Laboratory, Sheba Medical Center, Tel-Hashomer.,Sackler Faculty of Medicine, Tel Aviv University, Jerusalem, Israel
| | - Guntram A Grassl
- Research Center Borstel, Germany.,Institute for Medical Microbiology and Hospital Epidemiology, Hannover Medical School and German Center for Infection Research, Partner Site Hannover-Braunschweig
| | - Ohad Gal-Mor
- The Infectious Diseases Research Laboratory, Sheba Medical Center, Tel-Hashomer.,Department of Clinical Microbiology and Immunology, Jerusalem, Israel.,Sackler Faculty of Medicine, Tel Aviv University, Jerusalem, Israel
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7
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Azriel S, Goren A, Shomer I, Aviv G, Rahav G, Gal-Mor O. The Typhi colonization factor (Tcf) is encoded by multiple non-typhoidal Salmonella serovars but exhibits a varying expression profile and interchanging contribution to intestinal colonization. Virulence 2017; 8:1791-1807. [PMID: 28922626 DOI: 10.1080/21505594.2017.1380766] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
Abstract
Salmonella enterica serovars Typhi and Paratyphi A are human-restricted pathogens and the leading causative agents of enteric fever. The Typhi colonization factor (Tcf) is a chaperone-usher fimbria, thought to play a role in the host-specificity of typhoidal serovars. Here we show that the tcf cluster (tcfABCD tinR tioA) is present in at least 25 non-typhoidal Salmonella (NTS) serovars and demonstrate its native expression in clinically-important serovars including Schwarzengrund, 9,12:l,v:-, Choleraesuis, Bredeney, Heidelberg, Montevideo, Virchow and Infantis. Although the genetic organization of the tcf cluster is well conserved, the N-terminal half of the fimbrial adhesin, TcfD is highly diverse, suggesting different binding properties of distinct tcfD variants. Comparison of tcfA expression in typhoidal and NTS serovars demonstrated unexpected differences in its expression profiles, with the highest transcription levels in S. Typhi, S. Choleraesuis and S. Infantis. In the latter, tcf is induced in rich broth and under microaerobic conditions, characterizing the intestines of warm blooded animals. Furthermore, Tcf is negatively regulated by the ancestral leucine-responsive transcriptional regulator (Lrp). Using the colitis mouse model, we demonstrate that during mice infection tcfA is expressed at higher levels by S. Infantis than S. Schwarzengrund or S. Heidelberg. Moreover, while Tcf is dispensable for S. Schwarzengrund and S. Heidelberg mouse colonization, Tcf is involved in cecum and colon colonization by S. Infantis. Taken together, our results establish that Tcf is broadly encoded by multiple NTS serovars, but presents variable expression profiles and contributes differently to their virulence.
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Affiliation(s)
- Shalhevet Azriel
- a The Infectious Diseases Research Laboratory, Sheba Medical Center , Tel-Hashomer , Israel
| | - Alina Goren
- a The Infectious Diseases Research Laboratory, Sheba Medical Center , Tel-Hashomer , Israel.,b Department of Clinical Microbiology and Immunology , Tel-Aviv University , Tel-Aviv , Israel.,c Sackler Faculty of Medicine, Tel-Aviv University , Tel-Aviv , Israel
| | - Inna Shomer
- a The Infectious Diseases Research Laboratory, Sheba Medical Center , Tel-Hashomer , Israel
| | - Gili Aviv
- a The Infectious Diseases Research Laboratory, Sheba Medical Center , Tel-Hashomer , Israel.,b Department of Clinical Microbiology and Immunology , Tel-Aviv University , Tel-Aviv , Israel.,c Sackler Faculty of Medicine, Tel-Aviv University , Tel-Aviv , Israel
| | - Galia Rahav
- a The Infectious Diseases Research Laboratory, Sheba Medical Center , Tel-Hashomer , Israel.,c Sackler Faculty of Medicine, Tel-Aviv University , Tel-Aviv , Israel
| | - Ohad Gal-Mor
- a The Infectious Diseases Research Laboratory, Sheba Medical Center , Tel-Hashomer , Israel.,b Department of Clinical Microbiology and Immunology , Tel-Aviv University , Tel-Aviv , Israel.,c Sackler Faculty of Medicine, Tel-Aviv University , Tel-Aviv , Israel
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8
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Dawoud TM, Davis ML, Park SH, Kim SA, Kwon YM, Jarvis N, O’Bryan CA, Shi Z, Crandall PG, Ricke SC. The Potential Link between Thermal Resistance and Virulence in Salmonella: A Review. Front Vet Sci 2017; 4:93. [PMID: 28660201 PMCID: PMC5469892 DOI: 10.3389/fvets.2017.00093] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2017] [Accepted: 06/01/2017] [Indexed: 12/19/2022] Open
Abstract
In some animals, the typical body temperature can be higher than humans, for example, 42°C in poultry and 40°C in rabbits which can be a potential thermal stress challenge for pathogens. Even in animals with lower body temperatures, when infection occurs, the immune system may increase body temperature to reduce the chance of survival for pathogens. However, some pathogens can still easily overcome higher body temperatures and/or rise in body temperatures through expression of stress response mechanisms. Salmonella is the causative agent of one of the most prevalent foodborne illnesses, salmonellosis, and can readily survive over a wide range of temperatures due to the efficient expression of the heat (thermal) stress response. Therefore, thermal resistance mechanisms can provide cross protection against other stresses including the non-specific host defenses found within the human body thus increasing pathogenic potential. Understanding the molecular mechanisms associated with thermal responses in Salmonella is crucial in designing and developing more effective or new treatments for reducing and eliminating infection caused by Salmonella that have survived heat stress. In this review, Salmonella thermal resistance is assessed followed by an overview of the thermal stress responses with a focus on gene regulation by sigma factors, heat shock proteins, along with the corresponding thermosensors and their association with virulence expression including a focus on a potential link between heat resistance and potential for infection.
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Affiliation(s)
- Turki M. Dawoud
- Cell and Molecular Biology Program, University of Arkansas, Fayetteville, AR, United States
- Center for Food Safety, University of Arkansas, Fayetteville, AR, United States
| | - Morgan L. Davis
- Center for Food Safety, University of Arkansas, Fayetteville, AR, United States
- Department of Food Science, University of Arkansas, Fayetteville, AR, United States
| | - Si Hong Park
- Center for Food Safety, University of Arkansas, Fayetteville, AR, United States
- Department of Food Science, University of Arkansas, Fayetteville, AR, United States
| | - Sun Ae Kim
- Center for Food Safety, University of Arkansas, Fayetteville, AR, United States
- Department of Food Science, University of Arkansas, Fayetteville, AR, United States
| | - Young Min Kwon
- Cell and Molecular Biology Program, University of Arkansas, Fayetteville, AR, United States
- Center for Food Safety, University of Arkansas, Fayetteville, AR, United States
- Department of Poultry Science, University of Arkansas, Fayetteville, AR, United States
| | - Nathan Jarvis
- Center for Food Safety, University of Arkansas, Fayetteville, AR, United States
- Department of Food Science, University of Arkansas, Fayetteville, AR, United States
| | - Corliss A. O’Bryan
- Center for Food Safety, University of Arkansas, Fayetteville, AR, United States
- Department of Food Science, University of Arkansas, Fayetteville, AR, United States
| | - Zhaohao Shi
- Center for Food Safety, University of Arkansas, Fayetteville, AR, United States
- Department of Food Science, University of Arkansas, Fayetteville, AR, United States
| | - Philip G. Crandall
- Center for Food Safety, University of Arkansas, Fayetteville, AR, United States
- Department of Food Science, University of Arkansas, Fayetteville, AR, United States
| | - Steven C. Ricke
- Cell and Molecular Biology Program, University of Arkansas, Fayetteville, AR, United States
- Center for Food Safety, University of Arkansas, Fayetteville, AR, United States
- Department of Food Science, University of Arkansas, Fayetteville, AR, United States
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9
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Guijarro JA, Cascales D, García-Torrico AI, García-Domínguez M, Méndez J. Temperature-dependent expression of virulence genes in fish-pathogenic bacteria. Front Microbiol 2015. [PMID: 26217329 PMCID: PMC4496569 DOI: 10.3389/fmicb.2015.00700] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Virulence gene expression in pathogenic bacteria is modulated by environmental parameters. A key factor in this expression is temperature. Its effect on virulence gene expression in bacteria infecting warm-blooded hosts is well documented. Transcription of virulence genes in these bacteria is induced upon a shift from low environmental to a higher host temperature (37°C). Interestingly, host temperatures usually correspond to the optimum for growth of these pathogenic bacteria. On the contrary, in ectothermic hosts such as fish, molluscs, and amphibians, infection processes generally occur at a temperature lower than that for the optimal growth of the bacteria. Therefore, regulation of virulence gene expression in response to temperature shift has to be modulated in a different way to that which is found in bacteria infecting warm-blooded hosts. The current understanding of virulence gene expression and its regulation in response to temperature in fish-pathogenic bacteria is limited, but constant extension of our knowledge base is essential to enable a rational approach to the problem of the bacterial fish diseases affecting the aquaculture industry. This is an interesting issue and progress needs to be made in order to diminish the economic losses caused by these diseases. The intention of this review is, for the first time, to compile the scattered results existing in the field in order to lay the groundwork for future research. This article is an overview of those relevant virulence genes that are expressed at temperatures lower than that for optimal bacterial growth in different fish-pathogenic bacteria as well as the principal mechanisms that could be involved in their regulation.
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Affiliation(s)
- José A. Guijarro
- *Correspondence: José A. Guijarro, Área de Microbiología, Departamento de Biología Funcional, Facultad de Medicina, Instituto de Biotecnología de Asturias, Universidad de Oviedo, C/Julían Clavería 6, 33006 Oviedo, Spain,
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10
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Aviv G, Tsyba K, Steck N, Salmon-Divon M, Cornelius A, Rahav G, Grassl GA, Gal-Mor O. A unique megaplasmid contributes to stress tolerance and pathogenicity of an emergent Salmonella enterica serovar Infantis strain. Environ Microbiol 2014; 16:977-94. [PMID: 24320043 DOI: 10.1111/1462-2920.12351] [Citation(s) in RCA: 138] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2013] [Accepted: 11/30/2013] [Indexed: 11/30/2022]
Abstract
Of all known Salmonella enterica serovars, S. Infantis is one of the most commonly isolated and has been recently emerging worldwide. To understand the recent emergence of S. Infantis in Israel, we performed extensive comparative analyses between pre-emergent and the clonal emergent S. Infantis populations. We demonstrate the fixation of adaptive mutations in the DNA gyrase (gyrA) and nitroreductase (nfsA) genes, conferring resistance to quinolones and nitrofurans, respectively, and the carriage of an emergent-specific plasmid, designated pESI. This self-transferred episome is a mosaic megaplasmid (∼280 kb), which increases bacterial tolerance to environmental mercury (mer operon) and oxidative stress, and provides further resistance to tetracycline, sulfamethoxazole and trimethoprim, most likely due to the presence of tetRA, sulI and dfrA genes respectively. Moreover, pESI carries the yersiniabactin siderophore system and two novel chaperone-usher fimbriae. In vitro studies established that pESI conjugation into a plasmidless S. Infantis strain results in superior biofilm formation, adhesion and invasion into avian and mammalian host cells. In vivo mouse infections demonstrated higher pathogenicity and increased intestinal inflammation caused by an S. Infantis strain harboring pESI compared with the plasmidless parental strain. Our results indicate that the presence of pESI that was found only in the emergent population of S. Infantis in Israel contributes significantly to antimicrobials tolerance and pathogenicity of its carrier. It is highly likely that pESI plays a key role in the successful spread of the emergent clone that replaced the local S. Infantis community in the short time of only 2-3 years.
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Affiliation(s)
- Gili Aviv
- The Infectious Diseases Research Laboratory, Tel-Hashomer, Israel; Sackler Faculty of Medicine, Tel Aviv University, Israel
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11
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Steinmann R, Dersch P. Thermosensing to adjust bacterial virulence in a fluctuating environment. Future Microbiol 2013; 8:85-105. [PMID: 23252495 DOI: 10.2217/fmb.12.129] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The lifecycle of most microbial pathogens can be divided into two states: existence outside and inside their hosts. The sudden temperature upshift experienced upon entry from environmental or vector reservoirs into a warm-blooded host is one of the most crucial signals informing the pathogens to adjust virulence gene expression and their host-stress survival program. This article reviews the plethora of sophisticated strategies that bacteria have evolved to sense temperature, and outlines the molecular signal transduction mechanisms used to modulate synthesis of crucial virulence determinants. The molecular details of thermal control through conformational changes of DNA, RNA and proteins are summarized, complex and diverse thermosensing principles are introduced and their potential as drug targets or synthetic tools are discussed.
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Affiliation(s)
- Rebekka Steinmann
- Department of Molecular Infection Biology, Helmholtz Centre for Infection Research, Braunschweig, Germany
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Suez J, Porwollik S, Dagan A, Marzel A, Schorr YI, Desai PT, Agmon V, McClelland M, Rahav G, Gal-Mor O. Virulence gene profiling and pathogenicity characterization of non-typhoidal Salmonella accounted for invasive disease in humans. PLoS One 2013; 8:e58449. [PMID: 23505508 PMCID: PMC3591323 DOI: 10.1371/journal.pone.0058449] [Citation(s) in RCA: 128] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2012] [Accepted: 02/05/2013] [Indexed: 12/27/2022] Open
Abstract
Human infection with non-typhoidal Salmonella serovars (NTS) infrequently causes invasive systemic disease and bacteremia. To understand better the nature of invasive NTS (iNTS), we studied the gene content and the pathogenicity of bacteremic strains from twelve serovars (Typhimurium, Enteritidis, Choleraesuis, Dublin, Virchow, Newport, Bredeney, Heidelberg, Montevideo, Schwarzengrund, 9,12:l,v:- and Hadar). Comparative genomic hybridization using a Salmonella enterica microarray revealed a core of 3233 genes present in all of the iNTS strains, which include the Salmonella pathogenicity islands 1-5, 9, 13, 14; five fimbrial operons (bcf, csg, stb, sth, sti); three colonization factors (misL, bapA, sinH); and the invasion gene, pagN. In the iNTS variable genome, we identified 16 novel genomic islets; various NTS virulence factors; and six typhoid-associated virulence genes (tcfA, cdtB, hlyE, taiA, STY1413, STY1360), displaying a wider distribution among NTS than was previously known. Characterization of the bacteremic strains in C3H/HeN mice showed clear differences in disease manifestation. Previously unreported characterization of serovars Schwarzengrund, 9,12:l,v:-, Bredeney and Virchow in the mouse model showed low ability to elicit systemic disease, but a profound and elongated shedding of serovars Schwarzengrund and 9,12:l,v:- (as well as Enteritidis and Heidelberg) due to chronic infection of the mouse. Phenotypic comparison in macrophages and epithelial cell lines demonstrated a remarkable intra-serovar variation, but also showed that S. Typhimurium bacteremic strains tend to present lower intracellular growth than gastroenteritis isolates. Collectively, our data demonstrated a common core of virulence genes, which might be required for invasive salmonellosis, but also an impressive degree of genetic and phenotypic heterogeneity, highlighting that bacteremia is a complex phenotype, which cannot be attributed merely to an enhanced invasion or intracellular growth of a particular strain.
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Affiliation(s)
- Jotham Suez
- The Infectious Diseases Research Laboratory, Sheba Medical Center, Tel-Hashomer, Israel
- Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Steffen Porwollik
- The Vaccine Research Institute of San Diego, San Diego, California, United States of America
| | - Amir Dagan
- The Infectious Diseases Research Laboratory, Sheba Medical Center, Tel-Hashomer, Israel
| | - Alex Marzel
- The Infectious Diseases Research Laboratory, Sheba Medical Center, Tel-Hashomer, Israel
- Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Yosef Ilan Schorr
- Government Central Laboratories, Ministry of Health, Jerusalem, Israel
| | - Prerak T. Desai
- The Vaccine Research Institute of San Diego, San Diego, California, United States of America
| | - Vered Agmon
- Government Central Laboratories, Ministry of Health, Jerusalem, Israel
| | - Michael McClelland
- The Vaccine Research Institute of San Diego, San Diego, California, United States of America
- Department of Pathology and Laboratory Medicine, University of California Irvine, Irvine, California, United States of America
| | - Galia Rahav
- The Infectious Diseases Research Laboratory, Sheba Medical Center, Tel-Hashomer, Israel
- Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Ohad Gal-Mor
- The Infectious Diseases Research Laboratory, Sheba Medical Center, Tel-Hashomer, Israel
- * E-mail:
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Genome expression analysis of nonproliferating intracellular Salmonella enterica serovar Typhimurium unravels an acid pH-dependent PhoP-PhoQ response essential for dormancy. Infect Immun 2012; 81:154-65. [PMID: 23090959 DOI: 10.1128/iai.01080-12] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Genome-wide expression analyses have provided clues on how Salmonella proliferates inside cultured macrophages and epithelial cells. However, in vivo studies show that Salmonella does not replicate massively within host cells, leaving the underlying mechanisms of such growth control largely undefined. In vitro infection models based on fibroblasts or dendritic cells reveal limited proliferation of the pathogen, but it is presently unknown whether these phenomena reflect events occurring in vivo. Fibroblasts are distinctive, since they represent a nonphagocytic cell type in which S. enterica serovar Typhimurium actively attenuates intracellular growth. Here, we show in the mouse model that S. Typhimurium restrains intracellular growth within nonphagocytic cells positioned in the intestinal lamina propria. This response requires a functional PhoP-PhoQ system and is reproduced in primary fibroblasts isolated from the mouse intestine. The fibroblast infection model was exploited to generate transcriptome data, which revealed that ∼2% (98 genes) of the S. Typhimurium genome is differentially expressed in nongrowing intracellular bacteria. Changes include metabolic reprogramming to microaerophilic conditions, induction of virulence plasmid genes, upregulation of the pathogenicity islands SPI-1 and SPI-2, and shutdown of flagella production and chemotaxis. Comparison of relative protein levels of several PhoP-PhoQ-regulated functions (PagN, PagP, and VirK) in nongrowing intracellular bacteria and extracellular bacteria exposed to diverse PhoP-PhoQ-inducing signals denoted a regulation responding to acidic pH. These data demonstrate that S. Typhimurium restrains intracellular growth in vivo and support a model in which dormant intracellular bacteria could sense vacuolar acidification to stimulate the PhoP-PhoQ system for preventing intracellular overgrowth.
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Gal-Mor O, Suez J, Elhadad D, Porwollik S, Leshem E, Valinsky L, McClelland M, Schwartz E, Rahav G. Molecular and cellular characterization of a Salmonella enterica serovar Paratyphi a outbreak strain and the human immune response to infection. CLINICAL AND VACCINE IMMUNOLOGY : CVI 2012; 19:146-56. [PMID: 22190395 PMCID: PMC3272918 DOI: 10.1128/cvi.05468-11] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/23/2011] [Accepted: 12/08/2011] [Indexed: 12/23/2022]
Abstract
Enteric fever is an invasive life-threatening systemic disease caused by the Salmonella enterica human-adapted serovars Typhi and Paratyphi. Increasing incidence of infections with Salmonella enterica serovar Paratyphi A and the spreading of its antibiotic-resistant derivates pose a significant health concern in some areas of the world. Herein, we describe a molecular and phenotypic characterization of an S. Paratyphi A strain accounted for a recent paratyphoid outbreak in Nepal that affected at least 37 travelers. Pulsed-field gel electrophoresis analysis of the outbreak isolates revealed one genetic clone (pulsotype), confirming a single infecting source. Genetic profiling of the outbreak strain demonstrated the contribution of specific bacteriophages as a prime source of genetic diversity among clinical isolates of S. Paratyphi A. Phenotypic characterization in comparison with the S. Paratyphi A ATCC 9150 reference sequenced strain showed differences in flagellar morphology and increased abilities of the outbreak strain with respect to its motility, invasion into nonphagocytic cells, intracellular multiplication, survival within macrophages, and higher induction of interleukin-8 (IL-8) secreted by host cells. Collectively, these differences suggest an enhanced virulence potential of this strain and demonstrate an interesting phenotypic variation among S. Paratyphi A isolates. In vivo profiling of 16 inflammatory cytokines in patients infected with the outbreak strain revealed a common profile of a remarkable gamma interferon (IFN-γ) induction together with elevated concentrations of tumor necrosis factor alpha (TNF-α), IL-6, IL-8, IL-10, and IL-15, but not IL-12, which was previously demonstrated as elevated in nontyphoidal Salmonella infections. This apparent profile implies a distinct immune response to paratyphoid infections.
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Affiliation(s)
- Ohad Gal-Mor
- Infectious Diseases Research Laboratory, Sheba Medical Center, Tel-Hashomer, Israel.
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15
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Abstract
Four different mechanisms have evolved in eubacteria to comply with changes in the environmental temperature. The underlying genetic mechanisms regulate gene expression at transcriptional, translational and posttranslational level. The high temperature response (HTR) is a reaction on increases in temperature and is mainly used by pathogenic bacteria when they enter their mammalian host. The temperature of 37°C causes induction of the virulent genes the products of which are only needed in this environment. The heat shock response (HSR) is induced by any sudden increase in temperature, allows the bacterial cell to adapt to this environmental stress factor and is shut off after adaptation. In a similar way the low temperature response (LTR) is a reaction to a new environment and leads to the constant expression of appropriate genes. In contrast, the cold shock response (CSR) includes turn off of the cold shock genes after adaptation to the low temperature. Sensors of temperature changes are specific DNA regions, RNA molecules or proteins and conformational changes have been identified as a common motif.
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Valdez Y, Ferreira RBR, Finlay BB. Molecular mechanisms of Salmonella virulence and host resistance. Curr Top Microbiol Immunol 2010; 337:93-127. [PMID: 19812981 DOI: 10.1007/978-3-642-01846-6_4] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Salmonella species can cause typhoid fever and gastroenteritis in humans and pose a global threat to human health. In order to establish a successful infection, Salmonella utilize a large number of genes encoding a variety of virulence factors. Different animal models of infection have been used to better understand the mechanisms underlying each disease including cattle, rodents, and nematodes. To date, a number of different bacterial virulence factors have been identified using such animal models, most of which are secreted by two type three secretion systems (T3SS) encoded within Salmonella pathogenicity islands (SPI) 1 and 2. These proteins alter various host cell pathways, facilitating the invasion of epithelial cells during infection, as well as the survival and replication of Salmonella inside phagocytic cells. On the other hand, host genetics and resistance also play a role in the susceptibility to Salmonella infection. The natural resistance-associated macrophage protein 1 (Nramp1), for example, is critical for host defense, since mice lacking Nramp1 fail to control bacterial replication and succumb to low doses of S. Typhimurium. In this chapter, we analyze the different pathogen and host factors that play a role in the dynamic interaction between Salmonella and its host and their impact on disease.
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Affiliation(s)
- Yanet Valdez
- Department of Microbiology and Immunology, Michael Smith Laboratories, University of British Columbia, Vancouver, British Columbia, Canada
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Soyer Y, Orsi RH, Rodriguez-Rivera LD, Sun Q, Wiedmann M. Genome wide evolutionary analyses reveal serotype specific patterns of positive selection in selected Salmonella serotypes. BMC Evol Biol 2009; 9:264. [PMID: 19912661 PMCID: PMC2784778 DOI: 10.1186/1471-2148-9-264] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2009] [Accepted: 11/14/2009] [Indexed: 11/10/2022] Open
Abstract
Background The bacterium Salmonella enterica includes a diversity of serotypes that cause disease in humans and different animal species. Some Salmonella serotypes show a broad host range, some are host restricted and exclusively associated with one particular host, and some are associated with one particular host species, but able to cause disease in other host species and are thus considered "host adapted". Five Salmonella genome sequences, representing a broad host range serotype (Typhimurium), two host restricted serotypes (Typhi [two genomes] and Paratyphi) and one host adapted serotype (Choleraesuis) were used to identify core genome genes that show evidence for recombination and positive selection. Results Overall, 3323 orthologous genes were identified in all 5 Salmonella genomes analyzed. Use of four different methods to assess homologous recombination identified 270 genes that showed evidence for recombination with at least one of these methods (false discovery rate [FDR] <10%). After exclusion of genes with evidence for recombination, site and branch specific models identified 41 genes as showing evidence for positive selection (FDR <20%), including a number of genes with confirmed or likely roles in virulence and ompC, a gene encoding an outer membrane protein, which has also been found to be under positive selection in other bacteria. A total of 8, 16, 7, and 5 genes showed evidence for positive selection in Choleraesuis, Typhi, Typhimurium, and Paratyphi branch analyses, respectively. Sequencing and evolutionary analyses of four genes in an additional 42 isolates representing 23 serotypes confirmed branch specific positive selection and recombination patterns. Conclusion Our data show that, among the four serotypes analyzed, (i) less than 10% of Salmonella genes in the core genome show evidence for homologous recombination, (ii) a number of Salmonella genes are under positive selection, including genes that appear to contribute to virulence, and (iii) branch specific positive selection contributes to the evolution of host restricted Salmonella serotypes.
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Affiliation(s)
- Yeşim Soyer
- Department of Food Science, Cornell University, 412 Stocking Hall, Ithaca, NY 14853, USA.
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Klinkert B, Narberhaus F. Microbial thermosensors. Cell Mol Life Sci 2009; 66:2661-76. [PMID: 19554260 PMCID: PMC11115684 DOI: 10.1007/s00018-009-0041-3] [Citation(s) in RCA: 126] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2009] [Revised: 03/27/2009] [Accepted: 04/21/2009] [Indexed: 12/27/2022]
Abstract
Temperature is among the most important of the parameters that free-living microbes monitor. Microbial physiology needs to be readjusted in response to sudden temperature changes. When the ambient temperature rises or drops to potentially harmful levels, cells mount protective stress responses--so-called heat or cold shock responses, respectively. Pathogenic microorganisms often respond to a temperature of around 37 degrees C by inducing virulence gene expression. There are two main ways in which temperature can be measured. Often, the consequences of a sudden temperature shift are detected. Such indirect signals are known to be the accumulation of denatured proteins (heat shock) or stalled ribosomes (cold shock). However, this article focuses solely on direct thermosensors. Since the conformation of virtually every biomolecule is susceptible to temperature changes, primary sensors include DNA, RNA, proteins and lipids.
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Affiliation(s)
- Birgit Klinkert
- Lehrstuhl für Biologie der Mikroorganismen, Ruhr-Universität Bochum, Universitätsstrasse 150, NDEF 06/783, 44780 Bochum, Germany
| | - Franz Narberhaus
- Lehrstuhl für Biologie der Mikroorganismen, Ruhr-Universität Bochum, Universitätsstrasse 150, NDEF 06/783, 44780 Bochum, Germany
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Herbst K, Bujara M, Heroven AK, Opitz W, Weichert M, Zimmermann A, Dersch P. Intrinsic thermal sensing controls proteolysis of Yersinia virulence regulator RovA. PLoS Pathog 2009; 5:e1000435. [PMID: 19468295 PMCID: PMC2676509 DOI: 10.1371/journal.ppat.1000435] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2008] [Accepted: 04/20/2009] [Indexed: 01/14/2023] Open
Abstract
Pathogens, which alternate between environmental reservoirs and a mammalian host, frequently use thermal sensing devices to adjust virulence gene expression. Here, we identify the Yersinia virulence regulator RovA as a protein thermometer. Thermal shifts encountered upon host entry lead to a reversible conformational change of the autoactivator, which reduces its DNA-binding functions and renders it more susceptible for proteolysis. Cooperative binding of RovA to its target promoters is significantly reduced at 37°C, indicating that temperature control of rovA transcription is primarily based on the autoregulatory loop. Thermally induced reduction of DNA-binding is accompanied by an enhanced degradation of RovA, primarily by the Lon protease. This process is also subject to growth phase control. Studies with modified/chimeric RovA proteins indicate that amino acid residues in the vicinity of the central DNA-binding domain are important for proteolytic susceptibility. Our results establish RovA as an intrinsic temperature-sensing protein in which thermally induced conformational changes interfere with DNA-binding capacity, and secondarily render RovA susceptible to proteolytic degradation. Temperature is one of the most crucial environmental signals sensed by pathogens to adjust expression of their virulence factors and host survival programs after entry from a cold external environment into a warm-blooded host. Thermo-induced structural changes in bent or supercoiled DNA or mRNA secondary structures are frequently used to modulate virulence gene transcription or translation. Here we introduce a unique alternative mechanism, in which a central regulator of Yersinia virulence (RovA) uses an in-built thermosensor to control its activity in order to modulate virulence gene expression. According to our results, small thermo-induced structural alterations reduce the DNA-binding capacity of the virulence regulator and render the protein more susceptible to proteolytic degradation by ATP-dependent proteases. Amino acids in the vicinity of the DNA-binding region appear to comprise the information required for proteolysis. We therefore postulate a model in which proteolytic degradation is in direct competition with the thermo-sensitive DNA-binding function of the regulator. This regulatory concept constitutes a new example of how microbial pathogens are able to rapidly adjust virulence-associated processes in the course of an infection.
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Affiliation(s)
- Katharina Herbst
- Institut für Mikrobiologie, Technische Universität Braunschweig, Braunschweig, Germany
- Abteilung Molekulare Infektionsbiologie, Helmholtz-Zentrum für Infektionsforschung, Braunschweig, Germany
| | - Matthias Bujara
- Institut für Mikrobiologie, Technische Universität Braunschweig, Braunschweig, Germany
| | - Ann Kathrin Heroven
- Institut für Mikrobiologie, Technische Universität Braunschweig, Braunschweig, Germany
- Abteilung Molekulare Infektionsbiologie, Helmholtz-Zentrum für Infektionsforschung, Braunschweig, Germany
| | - Wiebke Opitz
- Institut für Mikrobiologie, Technische Universität Braunschweig, Braunschweig, Germany
- Abteilung Molekulare Infektionsbiologie, Helmholtz-Zentrum für Infektionsforschung, Braunschweig, Germany
| | - Martin Weichert
- Institut für Mikrobiologie, Technische Universität Braunschweig, Braunschweig, Germany
| | - Ariane Zimmermann
- Institut für Mikrobiologie, Technische Universität Braunschweig, Braunschweig, Germany
| | - Petra Dersch
- Institut für Mikrobiologie, Technische Universität Braunschweig, Braunschweig, Germany
- Abteilung Molekulare Infektionsbiologie, Helmholtz-Zentrum für Infektionsforschung, Braunschweig, Germany
- * E-mail:
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A novel secretion pathway of Salmonella enterica acts as an antivirulence modulator during salmonellosis. PLoS Pathog 2008; 4:e1000036. [PMID: 18389060 PMCID: PMC2270342 DOI: 10.1371/journal.ppat.1000036] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2007] [Accepted: 03/03/2008] [Indexed: 01/08/2023] Open
Abstract
Salmonella spp. are Gram-negative enteropathogenic bacteria that infect a variety of vertebrate hosts. Like any other living organism, protein secretion is a fundamental process essential for various aspects of Salmonella biology. Herein we report the identification and characterization of a horizontally acquired, autonomous and previously unreported secretion pathway. In Salmonella enterica serovar Typhimurium, this novel secretion pathway is encoded by STM1669 and STM1668, designated zirT and zirS, respectively. We show that ZirT is localized to the bacterial outer membrane, expected to adopt a compact β-barrel conformation, and functions as a translocator for ZirS. ZirS is an exoprotein, which is secreted into the extracellular environment in a ZirT-dependent manner. The ZirTS secretion pathway was found to share several important features with two-partner secretion (TPS) systems and members of the intimin/invasin family of adhesions. We show that zirTS expression is affected by zinc; and that in vivo, induction of zirT occurs distinctively in Salmonella colonizing the small intestine, but not in systemic sites. Additionally, strong expression of zirT takes place in Salmonella shed in fecal pellets during acute and persistent infections of mice. Inactivation of ZirTS results in a hypervirulence phenotype of Salmonella during oral infection of mice. Cumulatively, these results indicate that the ZirTS pathway plays a unique role as an antivirulence modulator during systemic disease and is involved in fine-tuning a host–pathogen balance during salmonellosis. Bacteria of the Salmonella genus are important human pathogens and a leading cause of food-borne illness. Like for all other living organisms, protein secretion is a fundamental process, which is required for many different aspects of Salmonella biology including biogenesis of organelles, nutrient acquisition, and virulence. In this work we describe a new secretion pathway in Salmonella termed ZirTS. This pathway consists of an exported protein (ZirS) and a designated membrane translocator (ZirT), which mediates the secretion of ZirS to the extracellular milieu. Using a mouse model of Salmonella infection, we found that the ZirTS system is induced in Salmonella colonizing the small intestine and in Salmonella shed in fecal pellets during acute and persistent infections. Interestingly, inactivation of ZirTS results in a hypervirulence phenotype of Salmonella during oral infection of mice. These observations indicate that the ZirTS pathway plays a unique role as an antivirulence modulator and is involved in fine-tuning host–pathogen interactions during disease. Our study elucidates an emerging theme in pathogenesis emphasizing the importance of pathogens to limit their effects upon the cells they infect in order to achieve a balance with their host.
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