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Skliros D, Droubogiannis S, Kalloniati C, Katharios P, Flemetakis E. Perturbation of Quorum Sensing after the Acquisition of Bacteriophage Resistance Could Contribute to Novel Traits in Vibrio alginolyticus. Microorganisms 2023; 11:2273. [PMID: 37764117 PMCID: PMC10535087 DOI: 10.3390/microorganisms11092273] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2023] [Revised: 09/04/2023] [Accepted: 09/06/2023] [Indexed: 09/29/2023] Open
Abstract
Bacteria employ a wide range of molecular mechanisms to confer resistance to bacteriophages, and these mechanisms are continuously being discovered and characterized. However, there are instances where certain bacterial species, despite lacking these known mechanisms, can still develop bacteriophage resistance through intricate metabolic adaptation strategies, potentially involving mutations in transcriptional regulators or phage receptors. Vibrio species have been particularly useful for studying the orchestrated metabolic responses of Gram-negative marine bacteria in various challenges. In a previous study, we demonstrated that Vibrio alginolyticus downregulates the expression of specific receptors and transporters in its membrane, which may enable the bacterium to evade infection by lytic bacteriophages. In our current study, our objective was to explore how the development of bacteriophage resistance in Vibrio species disrupts the quorum-sensing cascade, subsequently affecting bacterial physiology and metabolic capacity. Using a real-time quantitative PCR (rt-QPCR) platform, we examined the expression pattern of quorum-sensing genes, auto-inducer biosynthesis genes, and cell density regulatory proteins in phage-resistant strains. Our results revealed that bacteriophage-resistant bacteria downregulate the expression of quorum-sensing regulatory proteins, such as LuxM, LuxN, and LuxP. This downregulation attenuates the normal perception of quorum-sensing peptides and subsequently diminishes the expression of cell density regulatory proteins, including LuxU, aphA, and LuxR. These findings align with the diverse phenotypic traits observed in the phage-resistant strains, such as altered biofilm formation, reduced planktonic growth, and reduced virulence. Moreover, the transcriptional depletion of aphA, the master regulator associated with low cell density, was linked to the downregulation of genes related to virulence. This phenomenon appears to be phage-specific, suggesting a finely tuned metabolic adaptation driven by phage-host interaction. These findings contribute to our understanding of the role of Vibrio species in microbial marine ecology and highlight the complex interplay between phage resistance, quorum sensing, and bacterial physiology.
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Affiliation(s)
- Dimitrios Skliros
- Laboratory of Molecular Biology, Department of Biotechnology, School of Applied Biology and Biotechnology, Agricultural University of Athens, 11855 Athens, Greece; (D.S.); (C.K.)
| | - Stavros Droubogiannis
- Institute of Marine Biology, Biotechnology and Aquaculture, Hellenic Centre for Marine Research, 71500 Heraklion, Greece; (S.D.); (P.K.)
| | - Chrysanthi Kalloniati
- Laboratory of Molecular Biology, Department of Biotechnology, School of Applied Biology and Biotechnology, Agricultural University of Athens, 11855 Athens, Greece; (D.S.); (C.K.)
- Department of Marine Sciences, University of the Aegean, 81100 Mytilene, Greece
| | - Pantelis Katharios
- Institute of Marine Biology, Biotechnology and Aquaculture, Hellenic Centre for Marine Research, 71500 Heraklion, Greece; (S.D.); (P.K.)
| | - Emmanouil Flemetakis
- Laboratory of Molecular Biology, Department of Biotechnology, School of Applied Biology and Biotechnology, Agricultural University of Athens, 11855 Athens, Greece; (D.S.); (C.K.)
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Hodges FJ, Torres VVL, Cunningham AF, Henderson IR, Icke C. Redefining the bacterial Type I protein secretion system. Adv Microb Physiol 2023; 82:155-204. [PMID: 36948654 DOI: 10.1016/bs.ampbs.2022.10.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Type I secretion systems (T1SS) are versatile molecular machines for protein transport across the Gram-negative cell envelope. The archetypal Type I system mediates secretion of the Escherichia coli hemolysin, HlyA. This system has remained the pre-eminent model of T1SS research since its discovery. The classic description of a T1SS is composed of three proteins: an inner membrane ABC transporter, a periplasmic adaptor protein and an outer membrane factor. According to this model, these components assemble to form a continuous channel across the cell envelope, an unfolded substrate molecule is then transported in a one-step mechanism, directly from the cytosol to the extracellular milieu. However, this model does not encapsulate the diversity of T1SS that have been characterized to date. In this review, we provide an updated definition of a T1SS, and propose the subdivision of this system into five subgroups. These subgroups are categorized as T1SSa for RTX proteins, T1SSb for non-RTX Ca2+-binding proteins, T1SSc for non-RTX proteins, T1SSd for class II microcins, and T1SSe for lipoprotein secretion. Although often overlooked in the literature, these alternative mechanisms of Type I protein secretion offer many avenues for biotechnological discovery and application.
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Affiliation(s)
- Freya J Hodges
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD, Australia
| | - Von Vergel L Torres
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD, Australia
| | - Adam F Cunningham
- Institute of Immunology and Immunotherapy, University of Birmingham, Birmingham, United Kingdom
| | - Ian R Henderson
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD, Australia.
| | - Christopher Icke
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD, Australia.
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Skåne A, Loose JSM, Vaaje-Kolstad G, Askarian F. Comparative proteomic profiling reveals specific adaption of Vibrio anguillarum to oxidative stress, iron deprivation and humoral components of innate immunity. J Proteomics 2022; 251:104412. [PMID: 34737109 DOI: 10.1016/j.jprot.2021.104412] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2021] [Revised: 10/05/2021] [Accepted: 10/13/2021] [Indexed: 12/25/2022]
Abstract
The gram-negative bacterium Vibrio (Listonella) anguillarum (VA) is the causative agent of vibriosis, a terminal hemorrhagic septicemia affecting the aquacultural industry across the globe. In the current study we used label-free quantitative proteomics to investigate how VA adapts to conditions that mimic defined aspects of vibriosis-related stress such as exposure to oxidative stress (H2O2), exposure to humoral factors of innate immunity through incubation with Atlantic salmon serum, and iron deprivation upon supplementation of 2,2'-dipyridyl (DIP) to the growth medium. We also investigated how regulation of virulence factors may be governed by the VA growth phase and availability of nutrients. All experimental conditions explored revealed stress-specific proteomic adaption of VA and only nine proteins were found to be commonly regulated in all conditions. A general observation made for all stress-related conditions was regulation of multiple metabolic pathways. Notably, iron deprivation and exposure to Atlantic salmon serum evoked upregulation of iron acquisition mechanisms. The findings made in the present study represent a source of potential virulence determinants that can be of use in the search for means to understand vibriosis. SIGNIFICANCE: Vibriosis in fish and shellfish caused by V. anguillarum (VA) is responsible for large economic losses in the aquaculture sector across the globe. However, not much is known about the defense mechanism of this pathogen to percept and adapt to the imposed stresses during infection. Analyzing the response of VA to multiple host-related physiochemical stresses, the quantitative proteomic analysis of the present study indicates modulation of several virulence determinants and key defense networks of this pathogen. Our findings provide a theoretical basis to enhance our understanding of VA pathogenesis and can be employed to improve current intervention strategies to control vibriosis in aquaculture.
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Affiliation(s)
- Anna Skåne
- Faculty of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences (NMBU), Ås, Norway
| | - Jennifer S M Loose
- Faculty of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences (NMBU), Ås, Norway
| | - Gustav Vaaje-Kolstad
- Faculty of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences (NMBU), Ås, Norway.
| | - Fatemeh Askarian
- Faculty of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences (NMBU), Ås, Norway; Department of Pediatrics, University of California San Diego, La Jolla, CA 92093, USA.
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Mekasha S, Linke D. Secretion Systems in Gram-Negative Bacterial Fish Pathogens. Front Microbiol 2022; 12:782673. [PMID: 34975803 PMCID: PMC8714846 DOI: 10.3389/fmicb.2021.782673] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2021] [Accepted: 11/24/2021] [Indexed: 12/17/2022] Open
Abstract
Bacterial fish pathogens are one of the key challenges in the aquaculture industry, one of the fast-growing industries worldwide. These pathogens rely on arsenal of virulence factors such as toxins, adhesins, effectors and enzymes to promote colonization and infection. Translocation of virulence factors across the membrane to either the extracellular environment or directly into the host cells is performed by single or multiple dedicated secretion systems. These secretion systems are often key to the infection process. They can range from simple single-protein systems to complex injection needles made from dozens of subunits. Here, we review the different types of secretion systems in Gram-negative bacterial fish pathogens and describe their putative roles in pathogenicity. We find that the available information is fragmented and often descriptive, and hope that our overview will help researchers to more systematically learn from the similarities and differences between the virulence factors and secretion systems of the fish-pathogenic species described here.
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Affiliation(s)
- Sophanit Mekasha
- Section for Genetics and Evolutionary Biology, Department of Biosciences, University of Oslo, Oslo, Norway
| | - Dirk Linke
- Section for Genetics and Evolutionary Biology, Department of Biosciences, University of Oslo, Oslo, Norway
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Hassan MA, Abd Allah NA, Mabrok M. Inevitable impact of some environmental stressors on the frequency and pathogenicity of marine vibriosis. AQUACULTURE 2021; 536:736447. [DOI: 10.1016/j.aquaculture.2021.736447] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/01/2023]
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Li YX, Wang NN, Zhou YX, Lin CG, Wu JS, Chen XQ, Chen GJ, Du ZJ. Planococcus maritimus ML1206 Isolated from Wild Oysters Enhances the Survival of Caenorhabditis elegans against Vibrio anguillarum. Mar Drugs 2021; 19:md19030150. [PMID: 33809116 PMCID: PMC7999227 DOI: 10.3390/md19030150] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2021] [Revised: 03/05/2021] [Accepted: 03/09/2021] [Indexed: 11/16/2022] Open
Abstract
With the widespread occurrence of aquaculture diseases and the broad application of antibiotics, drug-resistant pathogens have increasingly affected aquatic animals’ health. Marine probiotics, which live under high pressure in a saltwater environment, show high potential as a substitute for antibiotics in the field of aquatic disease control. In this study, twenty strains of non-hemolytic bacteria were isolated from the intestine of wild oysters and perch, and a model of Caenorhabditis elegans infected by Vibrio anguillarum was established. Based on the model, ML1206, which showed a 99% similarity of 16S rRNA sequence to Planococcus maritimus, was selected as a potential marine probiotic, with strong antibacterial capabilities and great acid and bile salt tolerance, to protect Caenorhabditis elegans from being damaged by Vibrio anguillarum. Combined with plate counting and transmission electron microscopy, it was found that strain ML1206 could significantly inhibit Vibrio anguillarum colonization in the intestinal tract of Caenorhabditis elegans. Acute oral toxicity tests in mice showed that ML1206 was safe and non-toxic. The real-time qPCR results showed a higher expression level of genes related to the antibacterial peptide (ilys-3) and detoxification (ugt-22, cyp-35A3, and cyp-14A3) in the group of Caenorhabditis elegans protected by ML1206 compared to the control group. It is speculated that ML1206, as a potential probiotic, may inhibit the infection caused by Vibrio anguillarum through stimulating Caenorhabditis elegans to secrete antibacterial effectors and detoxification proteins. This paper provides a new direction for screening marine probiotics and an experimental basis to support the potential application of ML1206 as a marine probiotic in aquaculture.
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Affiliation(s)
- Ying-Xiu Li
- Marine College, Shandong University, Weihai 264209, China; (Y.-X.L.); (N.-N.W.); (Y.-X.Z.); (C.-G.L.); (J.-S.W.); (X.-Q.C.)
| | - Nan-Nan Wang
- Marine College, Shandong University, Weihai 264209, China; (Y.-X.L.); (N.-N.W.); (Y.-X.Z.); (C.-G.L.); (J.-S.W.); (X.-Q.C.)
| | - Yan-Xia Zhou
- Marine College, Shandong University, Weihai 264209, China; (Y.-X.L.); (N.-N.W.); (Y.-X.Z.); (C.-G.L.); (J.-S.W.); (X.-Q.C.)
| | - Chun-Guo Lin
- Marine College, Shandong University, Weihai 264209, China; (Y.-X.L.); (N.-N.W.); (Y.-X.Z.); (C.-G.L.); (J.-S.W.); (X.-Q.C.)
| | - Jing-Shan Wu
- Marine College, Shandong University, Weihai 264209, China; (Y.-X.L.); (N.-N.W.); (Y.-X.Z.); (C.-G.L.); (J.-S.W.); (X.-Q.C.)
| | - Xin-Qi Chen
- Marine College, Shandong University, Weihai 264209, China; (Y.-X.L.); (N.-N.W.); (Y.-X.Z.); (C.-G.L.); (J.-S.W.); (X.-Q.C.)
| | - Guan-Jun Chen
- Marine College, Shandong University, Weihai 264209, China; (Y.-X.L.); (N.-N.W.); (Y.-X.Z.); (C.-G.L.); (J.-S.W.); (X.-Q.C.)
- State Key Laboratory of Microbial Technology, Shandong University, Jinan 250100, China
- Correspondence: (G.J.C.); (Z.-J.D.)
| | - Zong-Jun Du
- Marine College, Shandong University, Weihai 264209, China; (Y.-X.L.); (N.-N.W.); (Y.-X.Z.); (C.-G.L.); (J.-S.W.); (X.-Q.C.)
- State Key Laboratory of Microbial Technology, Shandong University, Jinan 250100, China
- Correspondence: (G.J.C.); (Z.-J.D.)
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Spatiotemporal Regulation of Vibrio Exotoxins by HlyU and Other Transcriptional Regulators. Toxins (Basel) 2020; 12:toxins12090544. [PMID: 32842612 PMCID: PMC7551375 DOI: 10.3390/toxins12090544] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2020] [Revised: 08/17/2020] [Accepted: 08/19/2020] [Indexed: 02/06/2023] Open
Abstract
After invading a host, bacterial pathogens secrete diverse protein toxins to disrupt host defense systems. To ensure successful infection, however, pathogens must precisely regulate the expression of those exotoxins because uncontrolled toxin production squanders energy. Furthermore, inappropriate toxin secretion can trigger host immune responses that are detrimental to the invading pathogens. Therefore, bacterial pathogens use diverse transcriptional regulators to accurately regulate multiple exotoxin genes based on spatiotemporal conditions. This review covers three major exotoxins in pathogenic Vibrio species and their transcriptional regulation systems. When Vibrio encounters a host, genes encoding cytolysin/hemolysin, multifunctional-autoprocessing repeats-in-toxin (MARTX) toxin, and secreted phospholipases are coordinately regulated by the transcriptional regulator HlyU. At the same time, however, they are distinctly controlled by a variety of other transcriptional regulators. How this coordinated but distinct regulation of exotoxins makes Vibrio species successful pathogens? In addition, anti-virulence strategies that target the coordinating master regulator HlyU and related future research directions are discussed.
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8
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Lemos ML, Balado M. Iron uptake mechanisms as key virulence factors in bacterial fish pathogens. J Appl Microbiol 2020; 129:104-115. [PMID: 31994331 DOI: 10.1111/jam.14595] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Revised: 01/19/2020] [Accepted: 01/23/2020] [Indexed: 12/29/2022]
Abstract
This review summarizes the current knowledge about iron uptake systems in bacterial fish pathogens and their involvement in the infective process. Like most animal pathogens, fish pathogens have evolved sophisticated iron uptake mechanisms some of which are key virulence factors for colonization of the host. Among these systems, siderophore production and heme uptake systems are the best studied in fish pathogenic bacteria. Siderophores like anguibactin or piscibactin, have been described in Vibrio and Photobacterium pathogens as key virulence factors to cause disease in fish. In many other bacterial fish pathogens production of siderophores was demonstrated but the compounds were not yet chemically characterized and their role in virulence was not determined. The role of heme uptake in virulence was not yet clearly elucidated in fish pathogens although there exist evidence that these systems are expressed in fish tissues during infection. The relationship of other systems, like Fe(II) transporters or the use of citrate as iron carrier, with virulence is also unclear. Future trends of research on all these iron uptake mechanisms in bacterial fish pathogens are also discussed.
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Affiliation(s)
- M L Lemos
- Department of Microbiology and Parasitology, Institute of Aquaculture, Universidade de Santiago de Compostela, Santiago de Compostela, Spain
| | - M Balado
- Department of Microbiology and Parasitology, Institute of Aquaculture, Universidade de Santiago de Compostela, Santiago de Compostela, Spain
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Lages MA, Balado M, Lemos ML. The Expression of Virulence Factors in Vibrio anguillarum Is Dually Regulated by Iron Levels and Temperature. Front Microbiol 2019; 10:2335. [PMID: 31681201 PMCID: PMC6803810 DOI: 10.3389/fmicb.2019.02335] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2019] [Accepted: 09/25/2019] [Indexed: 01/24/2023] Open
Abstract
Vibrio anguillarum causes a hemorrhagic septicemia that affects cold- and warm-water adapted fish species. The main goal of this work was to determine the temperature-dependent changes in the virulence factors that could explain the virulence properties of V. anguillarum for fish cultivated at different temperatures. We have found that although the optimal growth temperature is around 25°C, the degree of virulence of V. anguillarum RV22 is higher at 15°C. To explain this result, an RNA-Seq analysis was performed to compare the whole transcriptome profile of V. anguillarum RV22 cultured under low-iron availability at either 25 or 15°C, which would mimic the conditions that V. anguillarum finds during colonization of fish cultivated at warm- or cold-water temperatures. The comparative analysis of transcriptomes at high- and low-iron conditions showed profound metabolic adaptations to grow under low iron. These changes were characterized by a down-regulation of the energetic metabolism and the induction of virulence-related factors like biosynthesis of LPS, production of hemolysins and lysozyme, membrane transport, heme uptake, or production of siderophores. However, the expression pattern of virulence factors under iron limitation showed interesting differences at warm and cold temperatures. Chemotaxis, motility, as well as the T6SS1 genes are expressed at higher levels at 25°C than at 15°C. By contrast, hemolysin RTX pore-forming toxin, T6SS2, and the genes associated with exopolysaccharides synthesis were preferentially expressed at 15°C. Notably, at this temperature, the siderophore piscibactin system was strongly up-regulated. In contrast, at 25°C, piscibactin genes were down-regulated and the vanchrobactin siderophore system seems to supply all the necessary iron to the cell. The results showed that V. anguillarum adjusts the expression of virulence factors responding to two environmental signals, iron levels and temperature. Thus, the relative relevance of each virulence factor for each fish species could vary depending on the water temperature. The results give clues about the physiological adaptations that allow V. anguillarum to cause infections in different fishes and could be relevant for vaccine development against fish vibriosis.
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Affiliation(s)
- Marta A Lages
- Department of Microbiology and Parasitology, Institute of Aquaculture, Universidade de Santiago de Compostela, Santiago de Compostela, Spain
| | - Miguel Balado
- Department of Microbiology and Parasitology, Institute of Aquaculture, Universidade de Santiago de Compostela, Santiago de Compostela, Spain
| | - Manuel L Lemos
- Department of Microbiology and Parasitology, Institute of Aquaculture, Universidade de Santiago de Compostela, Santiago de Compostela, Spain
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Balado M, Lages MA, Fuentes-Monteverde JC, Martínez-Matamoros D, Rodríguez J, Jiménez C, Lemos ML. The Siderophore Piscibactin Is a Relevant Virulence Factor for Vibrio anguillarum Favored at Low Temperatures. Front Microbiol 2018; 9:1766. [PMID: 30116232 PMCID: PMC6083037 DOI: 10.3389/fmicb.2018.01766] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2018] [Accepted: 07/16/2018] [Indexed: 11/13/2022] Open
Abstract
Vibrio anguillarum causes vibriosis, a hemorrhagic septicaemia that affects many cultured marine fish species worldwide. Two catechol siderophores, vanchrobactin and anguibactin, were previously identified in this bacterium. While vanchrobactin is a chromosomally encoded system widespread in all pathogenic and environmental strains, anguibactin is a plasmid-encoded system restricted to serotype O1 strains. In this work, we have characterized, from a serotype O2 strain producing vanchrobactin, a novel genomic island containing a cluster of genes that would encode the synthesis of piscibactin, a siderophore firstly described in the fish pathogen Photobacterium damselae subsp. piscicida. The chemical characterization of this siderophore confirmed that some strains of V. anguillarum produce piscibactin. An in silico analysis of the available genomes showed that this genomic island is present in many of the highly pathogenic V. anguillarum strains lacking the anguibactin system. The construction of single and double biosynthetic mutants for vanchrobactin and piscibactin allowed us to study the contribution of each siderophore to iron uptake, cell fitness, and virulence. Although both siderophores are simultaneously produced, piscibactin constitute a key virulence factor to infect fish, while vanchrobactin seems to have a secondary role in virulence. In addition, a transcriptional analysis of the gene cluster encoding piscibactin in V. anguillarum showed that synthesis of this siderophore is favored at low temperatures, being the transcriptional activity of the biosynthetic genes three-times higher at 18°C than at 25°C. We also show that iron levels and temperature contribute to balance the synthesis of both siderophores.
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Affiliation(s)
- Miguel Balado
- Department of Microbiology and Parasitology, Institute of Aquaculture, Universidade de Santiago de Compostela, Santiago de Compostela, Spain
| | - Marta A Lages
- Department of Microbiology and Parasitology, Institute of Aquaculture, Universidade de Santiago de Compostela, Santiago de Compostela, Spain
| | - Juan C Fuentes-Monteverde
- Department of Chemistry, Faculty of Sciences and Center for Advanced Scientific Research (CICA), Universidade da Coruña, A Coruña, Spain
| | - Diana Martínez-Matamoros
- Department of Chemistry, Faculty of Sciences and Center for Advanced Scientific Research (CICA), Universidade da Coruña, A Coruña, Spain
| | - Jaime Rodríguez
- Department of Chemistry, Faculty of Sciences and Center for Advanced Scientific Research (CICA), Universidade da Coruña, A Coruña, Spain
| | - Carlos Jiménez
- Department of Chemistry, Faculty of Sciences and Center for Advanced Scientific Research (CICA), Universidade da Coruña, A Coruña, Spain
| | - Manuel L Lemos
- Department of Microbiology and Parasitology, Institute of Aquaculture, Universidade de Santiago de Compostela, Santiago de Compostela, Spain
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Guo RH, Lim JY, Tra My DN, Jo SJ, Park JU, Rhee JH, Kim YR. Vibrio vulnificus RtxA1 Toxin Expression Upon Contact With Host Cells Is RpoS-Dependent. Front Cell Infect Microbiol 2018; 8:70. [PMID: 29600196 PMCID: PMC5862816 DOI: 10.3389/fcimb.2018.00070] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2017] [Accepted: 02/27/2018] [Indexed: 12/18/2022] Open
Abstract
The expression of virulence genes in bacteria is known to be regulated by various environmental and host factors. Vibrio vulnificus, an estuarine bacterium, experiences a dramatic environmental change during its infection process. We reported that V. vulnificus RtxA1 toxin caused acute cell death only when close contact to host cells was allowed. A sigma factor RpoS is a very important regulator for the maximal survival of pathogens under stress conditions. Here, we studied the role of RpoS in V. vulnificus cytotoxicity and mouse lethality. The growth of rpoS mutant strain was comparable to that of wild-type in heart infusion (HI) media and DMEM with HeLa cell lysate. An rpoS mutation resulted in decreased cytotoxicity, which was restored by in trans complementation. Interestingly, host contact increased the expression and secretion of V. vulnificus RtxA1 toxin, which was decreased and delayed by the rpoS mutation. Transcription of the cytotoxic gene rtxA1 and its transporter rtxB1 was significantly increased after host factor contact, whereas the activity was decreased by the rpoS mutation. In contrast, the rpoS mutation showed no effect on the transcriptional activity of a cytolytic heamolysin gene (vvhA). Additionally, the LD50 of the rpoS mutant was 15-fold higher than that of the wild-type in specific pathogen-free CD-1 female mice. Taken together, these results show that RpoS regulates the expression of V. vulnificus RtxA1 toxin and its transporter upon host contact.
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Affiliation(s)
- Rui Hong Guo
- College of Pharmacy and Research Institute of Drug Development, Chonnam National University, Gwangju, South Korea
| | - Ju Young Lim
- College of Pharmacy and Research Institute of Drug Development, Chonnam National University, Gwangju, South Korea
| | - Duong Nu Tra My
- Department of Molecular Medicine, Chonnam National University, Gwangju, South Korea
| | - Se Jin Jo
- College of Pharmacy and Research Institute of Drug Development, Chonnam National University, Gwangju, South Korea
| | - Jung Up Park
- College of Pharmacy and Research Institute of Drug Development, Chonnam National University, Gwangju, South Korea
| | - Joon Haeng Rhee
- Department of Microbiology, Clinical Vaccine R&D Center, Chonnam National University Medical School, Gwangju, South Korea
| | - Young Ran Kim
- College of Pharmacy and Research Institute of Drug Development, Chonnam National University, Gwangju, South Korea
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Mou X, Spinard EJ, Hillman SL, Nelson DR. Isocitrate dehydrogenase mutation in Vibrio anguillarum results in virulence attenuation and immunoprotection in rainbow trout (Oncorhynchus mykiss). BMC Microbiol 2017; 17:217. [PMID: 29137620 PMCID: PMC5686843 DOI: 10.1186/s12866-017-1124-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2017] [Accepted: 11/02/2017] [Indexed: 11/28/2022] Open
Abstract
Background Vibrio anguillarum is an extracellular bacterial pathogen that is a causative agent of vibriosis in finfish and crustaceans with mortality rates ranging from 30% to 100%. Mutations in central metabolism (glycolysis and the TCA cycle) of intracellular pathogens often result in attenuated virulence due to depletion of required metabolic intermediates; however, it was not known whether mutations in central metabolism would affect virulence in an extracellular pathogen such as V. anguillarum. Results Seven central metabolism mutants were created and characterized with regard to growth in minimal and complex media, expression of virulence genes, and virulence in juvenile rainbow trout (Oncorhynchus mykiss). Only the isocitrate dehydrogenase (icd) mutant was attenuated in virulence against rainbow trout challenged by either intraperitoneal injection or immersion. Further, the icd mutant was shown to be immunoprotective against wild type V. anguillarum infection. There was no significant decrease in the expression of the three hemolysin genes detected by qRT-PCR. Additionally, only the icd mutant exhibited a significantly decreased growth yield in complex media. Growth yield was directly related to the abundance of glutamate. A strain with a restored wild type icd gene was created and shown to restore growth to a wild type cell density in complex media and pathogenicity in rainbow trout. Conclusions The data strongly suggest that a decreased growth yield, resulting from the inability to synthesize α-ketoglutarate, caused the attenuation despite normal levels of expression of virulence genes. Therefore, the ability of an extracellular pathogen to cause disease is dependent upon the availability of host-supplied nutrients for growth. Additionally, a live vaccine strain could be created from an icd deletion strain. Electronic supplementary material The online version of this article (10.1186/s12866-017-1124-1) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Xiangyu Mou
- Department of Cell and Molecular Biology, University of Rhode Island, Kingston, RI, 02881, USA.,Present Address: Division of Infectious Diseases, Massachusetts General Hospital, 65 Landsdowne St, Cambridge, MA, 02139, USA
| | - Edward J Spinard
- Department of Cell and Molecular Biology, University of Rhode Island, Kingston, RI, 02881, USA
| | - Shelby L Hillman
- Department of Cell and Molecular Biology, University of Rhode Island, Kingston, RI, 02881, USA
| | - David R Nelson
- Department of Cell and Molecular Biology, University of Rhode Island, Kingston, RI, 02881, USA.
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13
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Li Y, Ma Q. Iron Acquisition Strategies of Vibrio anguillarum. Front Cell Infect Microbiol 2017; 7:342. [PMID: 28791260 PMCID: PMC5524678 DOI: 10.3389/fcimb.2017.00342] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2017] [Accepted: 07/11/2017] [Indexed: 12/03/2022] Open
Abstract
The hemorrhagic septicemic disease vibriosis caused by Vibrio anguillarum shows noticeable similarities to invasive septicemia in humans, and in this case, the V. anguillarum–host system has the potential to serve as a model for understanding native eukaryotic host–pathogen interactions. Iron acquisition, as a fierce battle occurring between pathogenic V. anguillarum and the fish host, is a pivotal step for virulence. In this article, advances in defining the roles of iron uptake pathways in growth and virulence of V. anguillarum have been summarized, divided into five aspects, including siderophore biosynthesis and secretion, iron uptake, iron release, and regulation of iron uptake. Understanding the molecular mechanisms of iron acquisition will have important implications for the pathogenicity of this organism.
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Affiliation(s)
- Yingjie Li
- Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of SciencesQingdao, China.,Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and TechnologyQingdao, China
| | - Qingjun Ma
- Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of SciencesQingdao, China.,Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and TechnologyQingdao, China
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14
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Gardiner M, Bournazos AM, Maturana-Martinez C, Zhong L, Egan S. Exoproteome Analysis of the Seaweed Pathogen Nautella italica R11 Reveals Temperature-Dependent Regulation of RTX-Like Proteins. Front Microbiol 2017; 8:1203. [PMID: 28706511 PMCID: PMC5489592 DOI: 10.3389/fmicb.2017.01203] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2017] [Accepted: 06/13/2017] [Indexed: 12/29/2022] Open
Abstract
Climate fluctuations have been linked to an increased prevalence of disease in seaweeds, including the red alga Delisea pulchra, which is susceptible to a bleaching disease caused by the bacterium Nautella italica R11 under elevated seawater temperatures. To further investigate the role of temperature in the induction of disease by N. italica R11, we assessed the effect of temperature on the expression of the extracellular proteome (exoproteome) in this bacterium. Label-free quantitative mass spectrometry was used to identify 207 proteins secreted into supernatant fraction, which is equivalent to 5% of the protein coding genes in the N. italica R11 genome. Comparative analysis demonstrated that expression of over 30% of the N. italica R11 exoproteome is affected by temperature. The temperature-dependent proteins include traits that could facilitate the ATP-dependent transport of amino acid and carbohydrate, as well as several uncharacterized proteins. Further, potential virulence determinants, including two RTX-like proteins, exhibited significantly higher expression in the exoproteome at the disease inducing temperature of 24°C relative to non-inducing temperature (16°C). This is the first study to demonstrate that temperature has an influence exoproteome expression in a macroalgal pathogen. The results have revealed several temperature regulated candidate virulence factors that may have a role in macroalgal colonization and invasion at elevated sea-surface temperatures, including novel RTX-like proteins.
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Affiliation(s)
- Melissa Gardiner
- School of Biological Earth and Environmental Sciences-Centre for Marine Bio-Innovation, The University of New South Wales, Sydney,NSW, Australia
| | - Adam M Bournazos
- School of Biological Earth and Environmental Sciences-Centre for Marine Bio-Innovation, The University of New South Wales, Sydney,NSW, Australia
| | - Claudia Maturana-Martinez
- School of Biological Earth and Environmental Sciences-Centre for Marine Bio-Innovation, The University of New South Wales, Sydney,NSW, Australia
| | - Ling Zhong
- Bioanalytical Mass Spectrometry Facility, Mark Wainwright Analytical Centre, The University of New South Wales, SydneyNSW, Australia
| | - Suhelen Egan
- School of Biological Earth and Environmental Sciences-Centre for Marine Bio-Innovation, The University of New South Wales, Sydney,NSW, Australia
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15
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Marana MH, Jørgensen LVG, Skov J, Chettri JK, Holm Mattsson A, Dalsgaard I, Kania PW, Buchmann K. Subunit vaccine candidates against Aeromonas salmonicida in rainbow trout Oncorhynchus mykiss. PLoS One 2017; 12:e0171944. [PMID: 28182704 PMCID: PMC5300222 DOI: 10.1371/journal.pone.0171944] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2016] [Accepted: 01/29/2017] [Indexed: 12/12/2022] Open
Abstract
Aeromonas salmonicida subsp. salmonicida is the etiological agent of furunculosis and a major fish health problem in salmonid aquaculture worldwide. Injection vaccination with commercial mineral oil-adjuvanted bacterin vaccines has been partly successful in preventing the disease but in Danish rainbow trout (Oncorhynchus mykiss, Walbaum) aquaculture furunculosis outbreaks still occur. In this study we tested the efficacy of experimental subunit vaccines against A. salmonicida infection in rainbow trout. We utilized in silico screening of the proteome of A. salmonicida subsp. salmonicida strain A449 and identified potential protective protein antigens that were tested by in vivo challenge trial. A total of 14 proteins were recombinantly expressed in Escherichia coli and prepared in 3 different subunit vaccine combinations to immunize 3 groups of rainbow trout by intraperitoneal (i.p.) injection. The fish were exposed to virulent A. salmonicida 7 weeks after immunization. To assess the efficacy of the subunit vaccines we evaluated the immune response in fish after immunization and challenge infection by measuring the antibody levels and monitoring the survival of fish in different groups. The survival of fish at 3 weeks after challenge infection showed that all 3 groups of fish immunized with 3 different protein combinations exhibited significantly lower mortalities (17–30%) compared to the control groups (48% and 56%). The ELISA results revealed significantly elevated antibody levels in fish against several protein antigens, which in some cases were positively correlated to the survival.
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Affiliation(s)
- Moonika Haahr Marana
- Department of Veterinary Disease Biology, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark
- * E-mail:
| | | | - Jakob Skov
- Department of Veterinary Disease Biology, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark
| | | | | | - Inger Dalsgaard
- National Veterinary Institute, Technical University of Denmark, Denmark
| | - Per Walter Kania
- Department of Veterinary Disease Biology, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark
| | - Kurt Buchmann
- Department of Veterinary Disease Biology, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark
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16
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Abstract
Multifunctional-autoprocessing repeats-in-toxin (MARTX) toxins are a heterogeneous group of toxins found in a number of Vibrio species and other Gram-negative bacteria. The toxins are composed of conserved repeat regions and an autoprocessing protease domain that together function as a delivery platform for transfer of cytotoxic and cytopathic domains into target eukaryotic cell cytosol. Within the cells, the effectors can alter biological processes such as signaling or cytoskeletal structure, presumably to the benefit of the bacterium. Ten effector domains are found in the various Vibrio MARTX toxins, although any one toxin carries only two to five effector domains. The specific toxin variant expressed by a species can be modified by homologous recombination to acquire or lose effector domains, such that different strains within the same species can express distinct variants of the toxins. This review examines the conserved structural elements of the MARTX toxins and details the different toxin arrangements carried by Vibrio species and strains. The catalytic function of domains and how the toxins are linked to pathogenesis of human and animals is described.
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17
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Gavin HE, Satchell KJF. MARTX toxins as effector delivery platforms. Pathog Dis 2015; 73:ftv092. [PMID: 26472741 DOI: 10.1093/femspd/ftv092] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/07/2015] [Indexed: 12/14/2022] Open
Abstract
Bacteria frequently manipulate their host environment via delivery of microbial 'effector' proteins to the cytosol of eukaryotic cells. In the case of the multifunctional autoprocessing repeats-in-toxins (MARTX) toxin, this phenomenon is accomplished by a single, >3500 amino acid polypeptide that carries information for secretion, translocation, autoprocessing and effector activity. MARTX toxins are secreted from bacteria by dedicated Type I secretion systems. The released MARTX toxins form pores in target eukaryotic cell membranes for the delivery of up to five cytopathic effectors, each of which disrupts a key cellular process. Targeted cellular processes include modulation or modification of small GTPases, manipulation of host cell signaling and disruption of cytoskeletal integrity. More recently, MARTX toxins have been shown to be capable of heterologous protein translocation. Found across multiple bacterial species and genera--frequently in pathogens lacking Type 3 or Type 4 secretion systems--MARTX toxins in multiple cases function as virulence factors. Innovative research at the intersection of toxin biology and bacterial genetics continues to elucidate the intricacies of the toxin as well as the cytotoxic mechanisms of its diverse effector collection.
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Affiliation(s)
- Hannah E Gavin
- Department of Microbiology-Immunology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
| | - Karla J F Satchell
- Department of Microbiology-Immunology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
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18
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McMillan S, Verner-Jeffreys D, Weeks J, Austin B, Desbois AP. Larva of the greater wax moth, Galleria mellonella, is a suitable alternative host for studying virulence of fish pathogenic Vibrio anguillarum. BMC Microbiol 2015; 15:127. [PMID: 26099243 PMCID: PMC4477312 DOI: 10.1186/s12866-015-0466-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2015] [Accepted: 06/12/2015] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND Microbial diseases cause considerable economic losses in aquaculture and new infection control measures often rely on a better understanding of pathogenicity. However, disease studies performed in fish hosts often require specialist infrastructure (e.g., aquaria), adherence to strict legislation and do not permit high-throughput approaches; these reasons justify the development of alternative hosts. This study aimed to validate the use of larvae of the greater wax moth (Galleria mellonella) to investigate virulence of the important fish pathogen, Vibrio anguillarum. RESULTS Using 11 wild-type isolates of V. anguillarum, these bacteria killed larvae in a dose-dependent manner and replicated inside the haemolymph, but infected larvae were rescued by antibiotic therapy. Crucially, virulence correlated significantly and positively in larva and Atlantic salmon (Salmo salar) infection models. Challenge studies with mutants knocked out for single virulence determinants confirmed conserved roles in larva and fish infections in some cases (pJM1 plasmid, rtxA), but not all (empA, flaA, flaE). CONCLUSIONS The G. mellonella model is simple, more ethically acceptable than experiments on vertebrates and, crucially, does not necessitate liquid systems, which reduces infrastructure requirements and biohazard risks associated with contaminated water. The G. mellonella model may aid our understanding of microbial pathogens in aquaculture and lead to the timely introduction of new effective remedies for infectious diseases, while adhering to the principles of replacement, reduction and refinement (3Rs) and considerably reducing the number of vertebrates used in such studies.
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Affiliation(s)
- Stuart McMillan
- Marine Biotechnology Research Group, Institute of Aquaculture, School of Natural Sciences, University of Stirling, Stirling, UK.
| | | | - Jason Weeks
- Centre for Environment, Fisheries and Aquaculture Science, Weymouth, UK. .,Present address: Department of Environmental Science and Technology, Cranfield University, Bedford, UK.
| | - Brian Austin
- Marine Biotechnology Research Group, Institute of Aquaculture, School of Natural Sciences, University of Stirling, Stirling, UK.
| | - Andrew P Desbois
- Marine Biotechnology Research Group, Institute of Aquaculture, School of Natural Sciences, University of Stirling, Stirling, UK.
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19
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Distinct roles of the repeat-containing regions and effector domains of the Vibrio vulnificus multifunctional-autoprocessing repeats-in-toxin (MARTX) toxin. mBio 2015; 6:mBio.00324-15. [PMID: 25827415 PMCID: PMC4453568 DOI: 10.1128/mbio.00324-15] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Vibrio vulnificus is a seafood-borne pathogen that destroys the intestinal epithelium, leading to rapid bacterial dissemination and death. The most important virulence factor is the multifunctional-autoprocessing repeats-in-toxin (MARTX) toxin comprised of effector domains in the center region flanked by long repeat-containing regions which are well conserved among MARTX toxins and predicted to translocate effector domains. Here, we examined the role of the repeat-containing regions using a modified V. vulnificus MARTX (MARTXVv) toxin generated by replacing all the internal effector domains with β-lactamase (Bla). Bla activity was detected in secretions from the bacterium and also in the cytosol of intoxicated epithelial cells. The modified MARTXVv toxin without effector domains retained its necrotic activity but lost its cell-rounding activity. Further, deletion of the carboxyl-terminal repeat-containing region blocked toxin secretion from the bacterium. Deletion of the amino-terminal repeat-containing region had no effect on secretion but completely abolished translocation and necrosis. Neither secretion nor translocation was affected by enzymatically inactivating the cysteine protease domain of the toxin. These data demonstrate that the amino-terminal and carboxyl-terminal repeat-containing regions of the MARTXVv toxin are necessary and sufficient for the delivery of effector domains and epithelial cell lysis in vitro but that effector domains are required for other cytopathic functions. Furthermore, Ca2+-dependent secretion of the modified MARTXVv toxin suggests that nonclassical RTX-like repeats found in the carboxyl-terminal repeat-containing region are functionally similar to classical RTX repeats found in other RTX proteins. Up to 95% of deaths from seafood-borne infections in the United States are due solely to one pathogen, V. vulnificus. Among its various virulence factors, the MARTXVv toxin has been characterized as a critical exotoxin for successful pathogenesis of V. vulnificus in mouse infection models. Similarly to MARTX toxins of other pathogens, MARTXVv toxin is comprised of repeat-containing regions, central effector domains, and an autoprocessing cysteine protease domain. Yet how each of these regions contributes to essential activities of the toxins has not been fully identified for any of MARTX toxins. Using modified MARTXVv toxin fused with β-lactamase as a reporter enzyme, the portion(s) responsible for toxin secretion from bacteria, effector domain translocation into host cells, rapid host cell rounding, and necrotic host cell death was identified. The results are relevant for understanding how MARTXVv toxin serves as both a necrotic pore-forming toxin and an effector delivery platform.
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20
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Gillespie JJ, Driscoll TP, Verhoeve VI, Utsuki T, Husseneder C, Chouljenko VN, Azad AF, Macaluso KR. Genomic diversification in strains of Rickettsia felis Isolated from different arthropods. Genome Biol Evol 2014; 7:35-56. [PMID: 25477419 PMCID: PMC4316617 DOI: 10.1093/gbe/evu262] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Rickettsia felis (Alphaproteobacteria: Rickettsiales) is the causative agent of an emerging flea-borne rickettsiosis with worldwide occurrence. Originally described from the cat flea, Ctenocephalides felis, recent reports have identified R. felis from other flea species, as well as other insects and ticks. This diverse host range for R. felis may indicate an underlying genetic variability associated with host-specific strains. Accordingly, to determine a potential genetic basis for host specialization, we sequenced the genome of R. felis str. LSU-Lb, which is an obligate mutualist of the parthenogenic booklouse Liposcelis bostrychophila (Insecta: Psocoptera). We also sequenced the genome of R. felis str. LSU, the second genome sequence for cat flea-associated strains (cf. R. felis str. URRWXCal2), which are presumably facultative parasites of fleas. Phylogenomics analysis revealed R. felis str. LSU-Lb diverged from the flea-associated strains. Unexpectedly, R. felis str. LSU was found to be divergent from R. felis str. URRWXCal2, despite sharing similar hosts. Although all three R. felis genomes contain the pRF plasmid, R. felis str. LSU-Lb carries an additional unique plasmid, pLbaR (plasmid of L. bostrychophila associated Rickettsia), nearly half of which encodes a unique 23-gene integrative conjugative element. Remarkably, pLbaR also encodes a repeats-in-toxin-like type I secretion system and associated toxin, heretofore unknown from other Rickettsiales genomes, which likely originated from lateral gene transfer with another obligate intracellular parasite of arthropods, Cardinium (Bacteroidetes). Collectively, our study reveals unexpected genomic diversity across three R. felis strains and identifies several diversifying factors that differentiate facultative parasites of fleas from obligate mutualists of booklice.
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Affiliation(s)
- Joseph J Gillespie
- Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, Maryland
| | | | - Victoria I Verhoeve
- Department of Pathobiological Sciences, Louisiana State University, School of Veterinary Medicine
| | - Tadanobu Utsuki
- Department of Pathobiological Sciences, Louisiana State University, School of Veterinary Medicine
| | - Claudia Husseneder
- Department of Entomology, Louisiana State University Agricultural Center, Baton Rouge, Louisiana
| | - Vladimir N Chouljenko
- Department of Pathobiological Sciences, Louisiana State University, School of Veterinary Medicine
| | - Abdu F Azad
- Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Kevin R Macaluso
- Department of Pathobiological Sciences, Louisiana State University, School of Veterinary Medicine
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21
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Mosca F, Ciulli S, Volpatti D, Romano N, Volpe E, Bulfon C, Massimini M, Caccia E, Galeotti M, Tiscar PG. Defensive response of European sea bass (Dicentrarchus labrax) against Listonella anguillarum or Photobacterium damselae subsp. piscicida experimental infection. Vet Immunol Immunopathol 2014; 162:83-95. [DOI: 10.1016/j.vetimm.2014.10.002] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2014] [Revised: 10/02/2014] [Accepted: 10/06/2014] [Indexed: 10/24/2022]
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Host specificity and clade dependent distribution of putative virulence genes in Moritella viscosa. Microb Pathog 2014; 77:53-65. [PMID: 25277600 DOI: 10.1016/j.micpath.2014.09.014] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2014] [Revised: 08/25/2014] [Accepted: 09/11/2014] [Indexed: 12/13/2022]
Abstract
Moritella viscosa is the aetiological agent of winter-ulcer disease in farmed salmonids in the North Atlantic. Previously, two major (typical and variant) genetic clades have been demonstrated within this bacterial species, one of which is almost solely related to disease in Atlantic salmon (Salmo salar). In the present study infection trials demonstrated that 'typical' M. viscosa isolated from Norwegian Atlantic salmon was highly virulent in this fish species but resulted in lower levels of mortality in rainbow trout. 'Variant' M. viscosa isolated from rainbow trout resulted in modest mortality levels in both Atlantic salmon and rainbow trout. To investigate the possible genetic background for inter-strain virulence differences, 38 M. viscosa isolates of diverse geographical origin and host species and a number of other Moritella spp. were investigated for the presence/absence of putative virulence related homologs. All isolates were positive for DNA sequences coding for; the Type VI secretion ATPase (clpV), hemolysin co-regulated protein (hcp), bacterioferritins (bfrA and bfrB), lectin (hemG), phospholipase D (pld), multifunctional autoprocessing repeats-in-toxin (martxA), aerolysin (aer), invasin (inv), and cytotoxic necrotizing factor (cnf), with the exception of one isolate in which cnf could not be confirmed. The product of an ABC transporter metal-binding lipoprotein (mat) was consistently detected although 11 isolates, all phylogenetically related, appear to produce a truncated version. A putative insecticidal toxin complex (mitABC) was detected almost exclusively in 'typical' Atlantic salmon isolates, and our data indicate that this complex of genes is expressed and co-transcribed. Transmission electron microscopy investigation revealed pili and flagella surface structures on nine M. viscosa representing both typical and variant isolates. Our results provide strong support for the existence of host specificity/high virulence in 'typical' M. viscosa related to Atlantic salmon. The gene distribution also provides further support for the genetic division within M. viscosa, and constitutes a basis for further study of the importance of the mitABC complex in winter-ulcer pathogenesis.
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Lux TM, Lee R, Love J. Genome-wide phylogenetic analysis of the pathogenic potential of Vibrio furnissii. Front Microbiol 2014; 5:435. [PMID: 25191313 PMCID: PMC4139957 DOI: 10.3389/fmicb.2014.00435] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2014] [Accepted: 07/31/2014] [Indexed: 11/15/2022] Open
Abstract
We recently reported the genome sequence of a free-living strain of Vibrio furnissii (NCTC 11218) harvested from an estuarine environment. V. furnissii is a widespread, free-living proteobacterium and emerging pathogen that can cause acute gastroenteritis in humans and lethal zoonoses in aquatic invertebrates, including farmed crustaceans and molluscs. Here we present the analyses to assess the potential pathogenic impact of V. furnissii. We compared the complete genome of V. furnissii with 8 other emerging and pathogenic Vibrio species. We selected and analyzed more deeply 10 genomic regions based upon unique or common features, and used 3 of these regions to construct a phylogenetic tree. Thus, we positioned V. furnissii more accurately than before and revealed a closer relationship between V. furnissii and V. cholerae than previously thought. However, V. furnissii lacks several important features normally associated with virulence in the human pathogens V. cholera and V. vulnificus. A striking feature of the V. furnissii genome is the hugely increased Super Integron, compared to the other Vibrio. Analyses of predicted genomic islands resulted in the discovery of a protein sequence that is present only in Vibrio associated with diseases in aquatic animals. We also discovered evidence of high levels horizontal gene transfer in V. furnissii. V. furnissii seems therefore to have a dynamic and fluid genome that could quickly adapt to environmental perturbation or increase its pathogenicity. Taken together, these analyses confirm the potential of V. furnissii as an emerging marine and possible human pathogen, especially in the developing, tropical, coastal regions that are most at risk from climate change.
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Affiliation(s)
- Thomas M Lux
- Biosciences, College of Life and Environmental Sciences, The University of Exeter Exeter, UK
| | - Rob Lee
- Biosciences, College of Life and Environmental Sciences, The University of Exeter Exeter, UK
| | - John Love
- Biosciences, College of Life and Environmental Sciences, The University of Exeter Exeter, UK
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24
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Karlsen C, Vanberg C, Mikkelsen H, Sørum H. Co-infection of Atlantic salmon (Salmo salar), by Moritella viscosa and Aliivibrio wodanis, development of disease and host colonization. Vet Microbiol 2014; 171:112-21. [PMID: 24745624 DOI: 10.1016/j.vetmic.2014.03.011] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2013] [Revised: 02/27/2014] [Accepted: 03/08/2014] [Indexed: 11/19/2022]
Abstract
Two species of bacteria are repeatedly isolated from farmed fish with winter-ulcer disease. Moritella viscosa is the aetiological agent of the disease; the significance of Aliivibrio wodanis is uncertain but has not been related to the primary pathogenesis. A cell culture infection model showed that A. wodanis adhered to, but did not invade the fish cells. Exposure to culture supernatant of A. wodanis caused the fish cells to vacoulate, retract, round up and detach from the surface, and rearrange the actin filaments of the cytoskeleton. These observations suggest that the bacterium secretes toxins into the extracellular environment. Any pathologic effect of A. wodanis and the effect of co-culturing with M. viscosa was studied in Atlantic salmon (Salmo salar) bath challenged with; only M. viscosa or only A. wodanis or both bacteria together. Both M. viscosa and A. wodanis were re-isolated from external surfaces and internal organs from live and deceased co-infected fish. It is further hypothesized that A. wodanis colonization might influence the progression of a M. viscosa infection. This is to our knowledge the first study that reproduces field observations where both bacteria infect Atlantic salmon.
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Affiliation(s)
- Christian Karlsen
- Department of Food Safety and Infection Biology, Norwegian School of Veterinary Science, P.O. Box 8146 Dep., 0033 Oslo, Norway.
| | - Christin Vanberg
- Department of Food Safety and Infection Biology, Norwegian School of Veterinary Science, P.O. Box 8146 Dep., 0033 Oslo, Norway
| | | | - Henning Sørum
- Department of Food Safety and Infection Biology, Norwegian School of Veterinary Science, P.O. Box 8146 Dep., 0033 Oslo, Norway
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Murugaiah C, Nik Mohd Noor NZ, Mustafa S, Manickam R, Pattabhiraman L. Construction and evaluation of V. cholerae O139 mutant, VCUSM21P, as a safe live attenuated cholera vaccine. PLoS One 2014; 9:e81817. [PMID: 24505241 PMCID: PMC3914778 DOI: 10.1371/journal.pone.0081817] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2013] [Accepted: 10/16/2013] [Indexed: 11/19/2022] Open
Abstract
Cholera is a major infectious disease, affecting millions of lives annually. In endemic areas, implementation of vaccination strategy against cholera is vital. As the use of safer live vaccine that can induce protective immunity against Vibrio cholerae O139 infection is a promising approach for immunization, we have designed VCUSM21P, an oral cholera vaccine candidate, which has ctxA that encodes A subunit of ctx and mutated rtxA/C, ace and zot mutations. VCUSM21P was found not to disassemble the actin of HEp2 cells. It colonized the mice intestine approximately 1 log lower than that of the Wild Type (WT) strain obtained from Hospital Universiti Sains Malaysia. In the ileal loop assay, unlike WT challenge, 1×106 and 1×108 colony forming unit (CFU) of VCUSM21P was not reactogenic in non-immunized rabbits. Whereas, the reactogenicity caused by the WT in rabbits immunized with 1×1010 CFU of VCUSM21P was found to be reduced as evidenced by absence of fluid in loops administered with 1×102–1×107 CFU of WT. Oral immunization using 1×1010 CFU of VCUSM21P induced both IgA and IgG against Cholera Toxin (CT) and O139 lipopolysaccharides (LPS). The serum vibriocidal antibody titer had a peak rise of 2560 fold on week 4. Following Removable Intestinal Tie Adult Rabbit Diarrhoea (RITARD) experiment, the non-immunized rabbits were found not to be protected against lethal challenge with 1×109 CFU WT, but 100% of immunized rabbits survived the challenge. In the past eleven years, V. cholerae O139 induced cholera has not been observed. However, attenuated VCUSM21P vaccine could be used for vaccination program against potentially fatal endemic or emerging cholera caused by V. cholerae O139.
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Affiliation(s)
- Chandrika Murugaiah
- School of Health Sciences, Universiti Sains Malaysia, Kubang Kerian, Kelantan, Malaysia
- Newcastle University Medicine Malaysia (NUMed), Nusajaya, Johor, Malaysia
- * E-mail:
| | - Nik Zuraina Nik Mohd Noor
- Department of Medical Microbiology and Parasitology, School of Medical Sciences, Universiti Sains Malaysia, Kubang Kerian, Kelantan, Malaysia
| | - Shyamoli Mustafa
- School of Health Sciences, Universiti Sains Malaysia, Kubang Kerian, Kelantan, Malaysia
| | - Ravichandran Manickam
- Department of Department of Biotechnology, AIMST University, Bedong, Kedah Darul Aman, Malaysia
| | - Lalitha Pattabhiraman
- Department of Department of Biotechnology, AIMST University, Bedong, Kedah Darul Aman, Malaysia
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Li L, Mou X, Nelson DR. Characterization of Plp, a phosphatidylcholine-specific phospholipase and hemolysin of Vibrio anguillarum. BMC Microbiol 2013; 13:271. [PMID: 24279474 PMCID: PMC4222444 DOI: 10.1186/1471-2180-13-271] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2013] [Accepted: 11/20/2013] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Vibrio anguillarum is the causative agent of vibriosis in fish. Several extracellular proteins secreted by V. anguillarum have been shown to contribute to virulence. While two hemolysin gene clusters, vah1-plp and rtxACHBDE, have been previously identified and described, the activities of the protein encoded by the plp gene were not known. Here we describe the biochemical activities of the plp-encoded protein and its role in pathogenesis. RESULTS The plp gene, one of the components in vah1 cluster, encodes a 416-amino-acid protein (Plp), which has homology to lipolytic enzymes containing the catalytic site amino acid signature SGNH. Hemolytic activity of the plp mutant increased 2-3-fold on sheep blood agar indicating that plp represses vah1; however, hemolytic activity of the plp mutant decreased by 2-3-fold on fish blood agar suggesting that Plp has different effects against erythrocytes from different species. His6-tagged recombinant Plp protein (rPlp) was over-expressed in E. coli. Purified and re-folded active rPlp exhibited phospholipase A2 activity against phosphatidylcholine and no activity against phosphatidylserine, phosphatidylethanolamine, or sphingomyelin. Characterization of rPlp revealed broad optimal activities at pH 5-9 and at temperatures of 30-64°C. Divalent cations and metal chelators did not affect activity of rPlp. We also demonstrated that Plp was secreted using thin layer chromatography and immunoblot analysis. Additionally, rPlp had strong hemolytic activity towards rainbow trout erythrocytes, but not to sheep erythrocytes suggesting that rPlp is optimized for lysis of phosphatidylcholine-rich fish erythrocytes. Further, only the loss of the plp gene had a significant effect on hemolytic activity of culture supernatant on fish erythrocytes, while the loss of rtxA and/or vah1 had little effect. However, V. anguillarum strains with mutations in plp or in plp and vah1 exhibited no significant reduction in virulence compared to the wild type strain when used to infect rainbow trout. CONCLUSION The plp gene of V. anguillarum encoding a phospholipase with A2 activity is specific for phosphatidylcholine and, therefore, able to lyse fish erythrocytes, but not sheep erythrocytes. Mutation of plp does not affect the virulence of V. anguillarum in rainbow trout.
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Affiliation(s)
- Ling Li
- Department of Cell and Molecular Biology, University of Rhode Island, 120 Flagg Rd,, Kingston, RI 02881, USA.
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Frans I, Dierckens K, Crauwels S, Van Assche A, Leisner J, Larsen MH, Michiels CW, Willems KA, Lievens B, Bossier P, Rediers H. Does virulence assessment of Vibrio anguillarum using sea bass (Dicentrarchus labrax) larvae correspond with genotypic and phenotypic characterization? PLoS One 2013; 8:e70477. [PMID: 23936439 PMCID: PMC3735585 DOI: 10.1371/journal.pone.0070477] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2013] [Accepted: 06/10/2013] [Indexed: 01/03/2023] Open
Abstract
BACKGROUND Vibriosis is one of the most ubiquitous fish diseases caused by bacteria belonging to the genus Vibrio such as Vibrio (Listonella) anguillarum. Despite a lot of research efforts, the virulence factors and mechanism of V. anguillarum are still insufficiently known, in part because of the lack of standardized virulence assays. METHODOLOGY/PRINCIPAL FINDINGS We investigated and compared the virulence of 15 V. anguillarum strains obtained from different hosts or non-host niches using a standardized gnotobiotic bioassay with European sea bass (Dicentrarchus labrax L.) larvae as model hosts. In addition, to assess potential relationships between virulence and genotypic and phenotypic characteristics, the strains were characterized by random amplified polymorphic DNA (RAPD) and repetitive extragenic palindromic PCR (rep-PCR) analyses, as well as by phenotypic analyses using Biolog's Phenotype MicroArray™ technology and some virulence factor assays. CONCLUSIONS/SIGNIFICANCE Virulence testing revealed ten virulent and five avirulent strains. While some relation could be established between serotype, genotype and phenotype, no relation was found between virulence and genotypic or phenotypic characteristics, illustrating the complexity of V. anguillarum virulence. Moreover, the standardized gnotobiotic system used in this study has proven its strength as a model to assess and compare the virulence of different V. anguillarum strains in vivo. In this way, the bioassay contributes to the study of mechanisms underlying virulence in V. anguillarum.
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Affiliation(s)
- Ingeborg Frans
- Laboratory for Process Microbial Ecology and Bioinspirational Management (PME&BIM), Thomas More Mechelen, Campus De Nayer, Department of Microbial and Molecular Systems (M2S), KU Leuven Association, Sint-Katelijne-Waver, Belgium
- Scientia Terrae Research Institute, Sint-Katelijne-Waver, Belgium
- Centre for Food and Microbial Technology, M2S, KU Leuven, Heverlee, Belgium
- Laboratory of Aquaculture and Artemia Reference Center, Department of Animal Production, Ghent University, Gent, Belgium
| | - Kristof Dierckens
- Laboratory of Aquaculture and Artemia Reference Center, Department of Animal Production, Ghent University, Gent, Belgium
| | - Sam Crauwels
- Laboratory for Process Microbial Ecology and Bioinspirational Management (PME&BIM), Thomas More Mechelen, Campus De Nayer, Department of Microbial and Molecular Systems (M2S), KU Leuven Association, Sint-Katelijne-Waver, Belgium
- Scientia Terrae Research Institute, Sint-Katelijne-Waver, Belgium
| | - Ado Van Assche
- Laboratory for Process Microbial Ecology and Bioinspirational Management (PME&BIM), Thomas More Mechelen, Campus De Nayer, Department of Microbial and Molecular Systems (M2S), KU Leuven Association, Sint-Katelijne-Waver, Belgium
- Scientia Terrae Research Institute, Sint-Katelijne-Waver, Belgium
| | - Jørgen Leisner
- Department of Veterinary Disease Biology, University of Copenhagen, Frederiksberg, Denmark
| | - Marianne H. Larsen
- Department of Veterinary Disease Biology, University of Copenhagen, Frederiksberg, Denmark
| | - Chris W. Michiels
- Centre for Food and Microbial Technology, M2S, KU Leuven, Heverlee, Belgium
| | - Kris A. Willems
- Laboratory for Process Microbial Ecology and Bioinspirational Management (PME&BIM), Thomas More Mechelen, Campus De Nayer, Department of Microbial and Molecular Systems (M2S), KU Leuven Association, Sint-Katelijne-Waver, Belgium
- Scientia Terrae Research Institute, Sint-Katelijne-Waver, Belgium
| | - Bart Lievens
- Laboratory for Process Microbial Ecology and Bioinspirational Management (PME&BIM), Thomas More Mechelen, Campus De Nayer, Department of Microbial and Molecular Systems (M2S), KU Leuven Association, Sint-Katelijne-Waver, Belgium
- Scientia Terrae Research Institute, Sint-Katelijne-Waver, Belgium
| | - Peter Bossier
- Laboratory of Aquaculture and Artemia Reference Center, Department of Animal Production, Ghent University, Gent, Belgium
| | - Hans Rediers
- Laboratory for Process Microbial Ecology and Bioinspirational Management (PME&BIM), Thomas More Mechelen, Campus De Nayer, Department of Microbial and Molecular Systems (M2S), KU Leuven Association, Sint-Katelijne-Waver, Belgium
- Scientia Terrae Research Institute, Sint-Katelijne-Waver, Belgium
- * E-mail:
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H-NS is a negative regulator of the two hemolysin/cytotoxin gene clusters in Vibrio anguillarum. Infect Immun 2013; 81:3566-76. [PMID: 23836825 DOI: 10.1128/iai.00506-13] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Hemolysins produced by Vibrio anguillarum have been implicated in the development of hemorrhagic septicemia during vibriosis, a fatal fish disease. Previously, two hemolysin gene clusters responsible for the hemolysis and cytotoxicity of V. anguillarum were identified: the vah1-plp gene cluster and the rtxACHBDE gene cluster. In this study, we identified the hns gene, which encodes the H-NS protein and acts as a negative regulator of both gene clusters. The V. anguillarum H-NS protein shares strong homology with other bacterial H-NS proteins. An hns mutant exhibited increased hemolytic activity and cytotoxicity compared to the wild-type strain. Complementation of the hns mutation restored hemolytic activity and cytotoxicity levels to nearly wild-type levels. Furthermore, expression of rtxA, rtxH, rtxB, vah1, and plp increased in the hns mutant and decreased in the hns-complemented mutant strain compared to expression in the wild-type strain. Additionally, experiments using DNase I showed that purified recombinant H-NS protected multiple sites in the promoter regions of both gene clusters. The hns mutant also exhibited significantly attenuated virulence against rainbow trout. Complementation of the hns mutation restored virulence to wild-type levels, suggesting that H-NS regulates many genes that affect fitness and virulence. Previously, we showed that HlyU is a positive regulator of expression for both gene clusters. In this study, we demonstrate that upregulation by hlyU is hns dependent, suggesting that H-NS acts to repress or silence both gene clusters and HlyU acts to relieve that repression or silencing.
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Two bifunctional enzymes with ferric reduction ability play complementary roles during magnetosome synthesis in Magnetospirillum gryphiswaldense MSR-1. J Bacteriol 2012; 195:876-85. [PMID: 23243303 DOI: 10.1128/jb.01750-12] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
The bacterial strain Magnetospirillum gryphiswaldense MSR-1 does not produce siderophores, but it absorbs a large amount of ferric iron and synthesizes magnetosomes. We demonstrated previously the presence of six types of ferric reductase isozymes (termed FeR1 through FeR6) in MSR-1. Of these isozymes, FeR5 was the most abundant and FeR6 showed the highest ferric reductase activity. In the present study, we cloned the fer5 and fer6 genes from MSR-1 and expressed them separately in Escherichia coli. FeR5 and FeR6 were shown to be bifunctional enzymes through analysis of amino acid sequence homologies, structural predictions (using data from GenBank), and detection of enzyme activities. FeR5 is a thioredoxin reductase and FeR6 is a flavin reductase, in addition to being ferric reductases. To elucidate the functions of the enzymes, we constructed two single-gene-deletion mutant strains (Δfer5 and Δfer6 mutants) and a double-gene-deletion mutant strain (Δfer5 Δfer6 [Δfer5+6] mutant) along with its complemented strains (C5 and C6). An evaluation of phenotypic and physiological properties did not reveal significant differences between the wild-type and single-gene-deletion strains, whereas the double-gene-deletion strain showed reduced iron absorption and no magnetosome synthesis. Complementation of the double-gene-deletion strain using either fer5 or fer6 resulted in the partial recovery of magnetosome synthesis. Quantitative real-time PCR analysis of fer5 and fer6 transcriptional levels in the wild-type and complemented strains demonstrated consistent transcription of the two genes and confirmed that FeR5 and FeR6 are bifunctional enzymes that play complementary roles during the process of magnetosome synthesis in MSR-1.
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Liu M, Crosa JH. The regulator HlyU, the repeat-in-toxin gene rtxA1, and their roles in the pathogenesis of Vibrio vulnificus infections. Microbiologyopen 2012; 1:502-13. [PMID: 23233275 PMCID: PMC3535394 DOI: 10.1002/mbo3.48] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2012] [Revised: 07/27/2012] [Accepted: 08/06/2012] [Indexed: 12/19/2022] Open
Abstract
HlyU is a master regulator that plays an essential role in the virulence of the human pathogen Vibrio vulnificus. One of the most noteworthy characteristics of HlyU regulation in this organism is its positive control of the expression of the repeat-in-toxin (RtxA1) gene, one of the most important virulence factors accounting for the fulminating and damaging nature of V. vulnificus infections. In this work, we reviewed the latest studies of RtxA1 in this bacterium and highlight the mechanism of gene regulation of rtxA1 expression by HlyU under a broader gene regulatory network.
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Affiliation(s)
- Moqing Liu
- Department of Molecular Microbiology and Immunology, Oregon Health and Science University, Portland, Oregon 97239, USA.
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Ahrens S, Geissler B, Satchell KJF. Identification of a His-Asp-Cys catalytic triad essential for function of the Rho inactivation domain (RID) of Vibrio cholerae MARTX toxin. J Biol Chem 2012. [PMID: 23184949 DOI: 10.1074/jbc.m112.396309] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Vibrio cholerae is the causative agent of the severe diarrheal disease cholera. For V. cholerae to colonize the intestinal epithelium, accessory toxins such as the multifunctional autoprocessing repeats-in-toxin (MARTX(Vc)) toxin are required. MARTX toxins are composite toxins comprised of arrayed effector domains that carry out distinct functions inside the host cell. Among the three effector domains of MARTX(Vc) is the Rho inactivation domain (RID(Vc)) known to cause cell rounding through inactivation of small RhoGTPases. Using alanine scanning mutagenesis in the activity subdomain of RID(Vc), four residues, His-2782, Leu-2851, Asp-2854, and Cys-3022, were identified as impacting RID(Vc) function in depolymerization of the actin cytoskeleton and inactivation of RhoA. Tyr-2807 and Tyr-3015 were identified as important potentially for forming the active structure for substrate contact but are not involved in catalysis or post translational modifications. Finally, V. cholerae strains modified to carry a catalytically inactive RID(Vc) show that the rate and efficiency of MARTX(Vc) actin cross-linking activity does not depend on a functional RID(Vc), demonstrating that these domains function independently in actin depolymerization. Overall, our results indicate a His-Asp-Cys catalytic triad is essential for function of the RID effector domain family shared by MARTX toxins produced by many Gram-negative bacteria.
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Affiliation(s)
- Sebastian Ahrens
- Department of Microbiology-Immunology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611, USA
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Park J, Kim SM, Jeong HG, Choi SH. Regulatory characteristics of the Vibrio vulnificus rtxHCA operon encoding a MARTX toxin. J Microbiol 2012; 50:878-81. [PMID: 22996810 DOI: 10.1007/s12275-012-2479-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2012] [Accepted: 09/06/2012] [Indexed: 12/19/2022]
Abstract
Vibrio vulnificus MARTX encoded by rtxA, an open reading frame of the rtxHCA operon, is essential for virulence in vitro and in mice. In this study, a primer extension analysis revealed that transcription of the rtxHCA operon begins at a single site, and is under the direction of a single promoter, P( rtxHCA ). P( rtxHCA ) activity appeared at the beginning of growth and reached a maximum in mid-exponential phase. P( rtxHCA ) activity was induced by exposure to INT-407 cells, and the membrane fraction of INT-407 cells was the most effective for the induction.
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Affiliation(s)
- Jinseo Park
- National Research Laboratory of Molecular Microbiology and Toxicology, Department of Agricultural Biotechnology, Center for Food Safety and Toxicology, Seoul National University, Seoul 151-921, Republic of Korea
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Actin cross-linking domain of Aeromonas hydrophila repeat in toxin A (RtxA) induces host cell rounding and apoptosis. Gene 2012; 506:369-76. [PMID: 22814176 DOI: 10.1016/j.gene.2012.07.012] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2012] [Revised: 06/15/2012] [Accepted: 07/09/2012] [Indexed: 11/24/2022]
Abstract
The repeat in toxin (Rtx) of an environmental isolate ATCC 7966 of Aeromonas hydrophila consists of six genes (rtxACHBDE) organized in an operon similar to the gene organization found for the Rtx of the Vibrio species. The first gene in this operon (rtxA) encodes an exotoxin in vibrios, while other genes code for proteins needed for proper activation of RtxA and in secretion of this toxin from Vibrio cholerae. However, the RtxA of ATCC 7966, as well as from the clinical isolate SSU of A. hydrophila, was exclusively expressed and produced during co-infection of this pathogen with the host, e.g., HeLa cells, indicating that rtxA gene expression required host cell contact. Within the RtxA, an actin cross-linking domain (ACD) exists and to investigate the functionality of this domain, several truncated versions of ACD were generated to discern its minimal biological active region. Such genetically modified genes encoding ACD, which were truncated on either the NH(2) or the COOH terminal, as well as on both ends, were expressed from a bidirectional promoter of the pBI-enhanced green fluorescent protein (EGFP) vector in a HeLa-Tet-Off cell system. We demonstrated that only the full-length ACD of RtxA from A. hydrophila catalyzed the covalent cross-linking of the host cellular actin, whereas the ACD truncated on the NH(2), COOH or both ends did not exhibit such actin cross-linking characteristics. Further, we showed that the full-length ACD of A. hydrophila RtxA disrupted the actin cytoskeleton of HeLa cells, resulting in their rounding phenotype. Finally, our data provided evidence that the full-length ACD of RtxA induced host cell apoptosis. Our study is the first to report that A. hydrophila possesses a functional RtxA having an ACD that contributes to the host cell apoptosis, and hence could represent a potential virulence factor of this emerging human pathogen.
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FeoB2 Functions in magnetosome formation and oxidative stress protection in Magnetospirillum gryphiswaldense strain MSR-1. J Bacteriol 2012; 194:3972-6. [PMID: 22636767 DOI: 10.1128/jb.00382-12] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Magnetotactic bacteria (MTB) synthesize unique organelles, the magnetosomes, which are intracellular nanometer-sized, membrane-enveloped magnetite. The biomineralization of magnetosomes involves the uptake of large amounts of iron. However, the iron metabolism of MTB is not well understood. The genome of the magnetotactic bacterium Magnetospirillum gryphiswaldense strain MSR-1 contains two ferrous iron transport genes, feoB1 and feoB2. The FeoB1 protein was reported to be responsible mainly for the transport of ferrous iron and to play an accessory role in magnetosome formation. To determine the role of feoB2, we constructed an feoB2 deletion mutant (MSR-1 ΔfeoB2) and an feoB1 feoB2 double deletion mutant (MSR-1 NfeoB). The single feoB2 mutation did not affect magnetite crystal biomineralization. MSR-1 NfeoB had a significantly lower average magnetosome number per cell (∼65%) than MSR-1 ΔfeoB1, indicating that FeoB2 plays a role in magnetosome formation when the feoB1 gene is deleted. Our findings showed that FeoB1 has a greater ferrous iron transport ability than FeoB2 and revealed the differential roles of FeoB1 and FeoB2 in MSR-1 iron metabolism. Interestingly, compared to the wild type, the feoB mutants showed increased sensitivity to oxidative stress and lower activities of the enzymes superoxide dismutase and catalase, indicating that the FeoB proteins help protect bacterial cells from oxidative stress.
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Satchell KJ. Structure and Function of MARTX Toxins and Other Large Repetitive RTX Proteins. Annu Rev Microbiol 2011; 65:71-90. [DOI: 10.1146/annurev-micro-090110-102943] [Citation(s) in RCA: 139] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Karla J.F. Satchell
- Department of Microbiology-Immunology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611;
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Frans I, Michiels CW, Bossier P, Willems KA, Lievens B, Rediers H. Vibrio anguillarum as a fish pathogen: virulence factors, diagnosis and prevention. JOURNAL OF FISH DISEASES 2011; 34:643-661. [PMID: 21838709 DOI: 10.1111/j.1365-2761.2011.01279.x] [Citation(s) in RCA: 262] [Impact Index Per Article: 20.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Vibrio anguillarum, also known as Listonella anguillarum, is the causative agent of vibriosis, a deadly haemorrhagic septicaemic disease affecting various marine and fresh/brackish water fish, bivalves and crustaceans. In both aquaculture and larviculture, this disease is responsible for severe economic losses worldwide. Because of its high morbidity and mortality rates, substantial research has been carried out to elucidate the virulence mechanisms of this pathogen and to develop rapid detection techniques and effective disease-prevention strategies. This review summarizes the current state of knowledge pertaining to V. anguillarum, focusing on pathogenesis, known virulence factors, diagnosis, prevention and treatment.
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Affiliation(s)
- I Frans
- Laboratory for Process Microbial Ecology and Bioinspirational Management, Consortium for Industrial Microbiology and Biotechnology, Department of Microbial and Molecular Systems, K.U. Leuven Association, Lessius Mechelen, Sint-Katelijne-Waver, Belgium
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Abstract
The two hemolysin gene clusters previously identified in Vibrio anguillarum, the vah1 cluster and the rtxACHBDE cluster, are responsible for the hemolytic and cytotoxic activities of V. anguillarum in fish. In this study, we used degenerate PCR to identify a positive hemolysin regulatory gene, hlyU, from the unsequenced V. anguillarum genome. The hlyU gene of V. anguillarum encodes a 92-amino-acid protein and is highly homologous to other bacterial HlyU proteins. An hlyU mutant was constructed, which exhibited an ∼5-fold decrease in hemolytic activity on sheep blood agar with no statistically significant decrease in cytotoxicity of the wild-type strain. Complementation of the hlyU mutation restored both hemolytic activity and cytotoxic activity. Both semiquantitative reverse transcription-PCR (RT-PCR) and quantitative real-time RT-PCR (qRT-PCR) were used to examine expression of the hemolysin genes under exponential and stationary-phase conditions in wild-type, hlyU mutant, and hlyU complemented strains. Compared to the wild-type strain, expression of rtx genes decreased in the hlyU mutant, while expression of vah1 and plp was not affected in the hlyU mutant. Complementation of the hlyU mutation restored expression of the rtx genes and increased vah1 and plp expression to levels higher than those in the wild type. The transcriptional start sites in both the vah1-plp and rtxH-rtxB genes' intergenic regions were determined using 5' random amplification of cDNA ends (5'-RACE), and the binding sites for purified HlyU were discovered using DNA gel mobility shift experiments and DNase protection assays.
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Complete genome sequence of the marine fish pathogen Vibrio anguillarum harboring the pJM1 virulence plasmid and genomic comparison with other virulent strains of V. anguillarum and V. ordalii. Infect Immun 2011; 79:2889-900. [PMID: 21576332 DOI: 10.1128/iai.05138-11] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We dissected the complete genome sequence of the O1 serotype strain Vibrio anguillarum 775(pJM1) and determined the draft genomic sequences of plasmidless strains of serotype O1 (strain 96F) and O2β (strain RV22) and V. ordalii. All strains harbor two chromosomes, but 775 also harbors the virulence plasmid pJM1, which carries the anguibactin-producing and cognate transport genes, one of the main virulence factors of V. anguillarum. Genomic analysis identified eight genomic islands in chromosome 1 of V. anguillarum 775(pJM1) and two in chromosome 2. Some of them carried potential virulence genes for the biosynthesis of O antigens, hemolysins, and exonucleases as well as others for sugar transport and metabolism. The majority of genes for essential cell functions and pathogenicity are located on chromosome 1. In contrast, chromosome 2 contains a larger fraction (59%) of hypothetical genes than does chromosome 1 (42%). Chromosome 2 also harbors a superintegron, as well as host "addiction" genes that are typically found on plasmids. Unique distinctive properties include homologues of type III secretion system genes in 96F, homologues of V. cholerae zot and ace toxin genes in RV22, and the biofilm formation syp genes in V. ordalii. Mobile genetic elements, some of them possibly originated in the pJM1 plasmid, were very abundant in 775, resulting in the silencing of specific genes, with only few insertions in the 96F and RV22 chromosomes.
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Tunsjø HS, Wiik-Nielsen CR, Grove S, Skjerve E, Sørum H, L'abée-Lund TM. Putative virulence genes in Moritella viscosa: activity during in vitro inoculation and in vivo infection. Microb Pathog 2011; 50:286-92. [PMID: 21334427 DOI: 10.1016/j.micpath.2011.02.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2010] [Revised: 01/27/2011] [Accepted: 02/04/2011] [Indexed: 11/30/2022]
Abstract
Moritella viscosa is considered to be the main aetiological agent of winter ulcer disease, primarily affecting farmed salmonid fish in cold marine waters. Transcription profiles of twelve M. viscosa genes, potentially involved in the pathogenesis, were studied during the course of an in vitro cell culture infection assay. Transcription of the same genes was compared in vivo, in head kidney and ulcer tissues of Atlantic salmon challenged with M. viscosa. During the in vitro infection, three putative toxins: a putative repeats in toxin gene (rtxA), a putative cytotoxic necrotizing factor (cnf) and a putative hemolysin increased their transcription significantly with time and coincident with cell rounding. Furthermore, the majority of the genes were stimulated by presence of fish cells and showed higher activity when adhered to fish cells compared to their planktonic counterpart. In vivo gene transcription studies revealed an up-regulation of a putative lateral flagellin in ulcer compared to head kidney tissues in the same individual. A similar trend was seen for cnf and a gene encoding a putative protease, indicating a role for these factors in colonization and tissue damage.
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Affiliation(s)
- Hege Smith Tunsjø
- Norwegian School of Veterinary Science, Department of Food Safety and Infection Biology, Pb 8146 Dep., 0033 Oslo, Norway
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Mutation of a novel virulence-related gene mltD in Vibrio anguillarum enhances lethality in zebra fish. Res Microbiol 2011; 162:144-50. [DOI: 10.1016/j.resmic.2010.08.003] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2010] [Accepted: 08/30/2010] [Indexed: 11/20/2022]
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Linhartová I, Bumba L, Mašín J, Basler M, Osička R, Kamanová J, Procházková K, Adkins I, Hejnová-Holubová J, Sadílková L, Morová J, Sebo P. RTX proteins: a highly diverse family secreted by a common mechanism. FEMS Microbiol Rev 2011; 34:1076-112. [PMID: 20528947 PMCID: PMC3034196 DOI: 10.1111/j.1574-6976.2010.00231.x] [Citation(s) in RCA: 360] [Impact Index Per Article: 27.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Repeats-in-toxin (RTX) exoproteins of Gram-negative bacteria form a steadily growing family of proteins with diverse biological functions. Their common feature is the unique mode of export across the bacterial envelope via the type I secretion system and the characteristic, typically nonapeptide, glycine- and aspartate-rich repeats binding Ca2+ ions. In this review, we summarize the current state of knowledge on the organization of rtx loci and on the biological and biochemical activities of therein encoded proteins. Applying several types of bioinformatic screens on the steadily growing set of sequenced bacterial genomes, over 1000 RTX family members were detected, with the biological functions of most of them remaining to be characterized. Activities of the so far characterized RTX family members are then discussed and classified according to functional categories, ranging from the historically first characterized pore-forming RTX leukotoxins, through the large multifunctional enzymatic toxins, bacteriocins, nodulation proteins, surface layer proteins, up to secreted hydrolytic enzymes exhibiting metalloprotease or lipase activities of industrial interest.
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Affiliation(s)
- Irena Linhartová
- Institute of Microbiology AS CR v.v.i., Academy of Sciences of the Czech Republic, Prague, Czech Republic
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Naka H, Crosa JH. Genetic Determinants of Virulence in the Marine Fish Pathogen Vibrio anguillarum. FISH PATHOLOGY 2011; 46:1-10. [PMID: 21625345 PMCID: PMC3103123 DOI: 10.3147/jsfp.46.1] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
One of the most studied fish pathogens is Vibrio anguillarum. Development of the genetics and biochemistry of the mechanisms of virulence in this fish pathogen together with clinical and ecologic studies has permitted the intensive development of microbiology in fish diseases. It is the intention of this review to compile the exhaustive knowledge accumulated on this bacterium and its interaction with the host fish by reporting a complete analysis of the V. anguillarum virulence factors and the genetics of their complexity.
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Domain organization and evolution of multifunctional autoprocessing repeats-in-toxin (MARTX) toxin in Vibrio vulnificus. Appl Environ Microbiol 2010; 77:657-68. [PMID: 21075892 DOI: 10.1128/aem.01806-10] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The objective of this study was to analyze multifunctional autoprocessing repeats-in-toxin (MARTX) toxin domain organization within the aquatic species Vibrio vulnificus as well as to study the evolution of the rtxA1 gene. The species is subdivided into three biotypes that differ in host range and geographical distribution. We have found three different types (I, II, and III) of V. vulnificus MARTX (MARTX(Vv)) toxins with common domains (an autocatalytic cysteine protease domain [CPD], an α/β-hydrolase domain, and a domain resembling that of the LifA protein of Escherichia coli O127:H6 E2348/69 [Efa/LifA]) and specific domains (a Rho-GTPase inactivation domain [RID], a domain of unknown function [DUF], a domain resembling that of the rtxA protein of Photorhabdus asymbiotica [rtxA(PA)], and an actin cross-linking domain [ACD]). Biotype 1 isolates harbor MARTX(Vv) toxin types I and II, biotype 2 isolates carry MARTX(Vv) toxin type III, and biotype 3 isolates have MARTX(Vv) toxin type II. The analyzed biotype 2 isolates harbor two identical copies of rtxA1, one chromosomal and the other plasmidic. The evolutionary history of the gene demonstrates that MARTX(Vv) toxins are mosaics, comprising pieces with different evolutionary histories, some of which have been acquired by intra- or interspecific horizontal gene transfer. Finally, we have found evidence that the evolutionary history of the rtxA1 gene for biotype 2 differs totally from the gene history of biotypes 1 and 3.
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Zou YX, Mo ZL, Hao B, Ye XH, Guo DS, Zhang PJ. Screening of genes expressed in vivo after infection by Vibrio anguillarum M3. Lett Appl Microbiol 2010; 51:564-9. [PMID: 20849396 DOI: 10.1111/j.1472-765x.2010.02935.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
AIMS Genes uniquely expressed in vivo may contribute to the overall pathogenicity of an organism and are likely to serve as potential targets for the development of new vaccine. This study aims to screen the genes expressed in vivo after Vibrio anguillarum infection by in vivo-induced antigen technology (IVIAT). METHODS AND RESULTS The convalescent-phase sera were obtained from turbot (Scophthalmus maximus) survived after infection by the virulent V. anguillarum M3. The pooled sera were thoroughly adsorbed with M3 cells and Escherichia coli BL21 (DE3) cells. A genomic expression library of M3 was constructed and screened for the identification of immunogenic proteins by colony immunoblot analysis with the adsorbed sera. After three rounds of screening, 19 putative in vivo-induced (ivi) genes were obtained. These ivi genes were catalogued into four functional groups: regulator/signalling, metabolism, biological process and hypothetical proteins. Three ivi genes were insertion-mutated, and the growth and 50% lethal dose (LD(50) ) of these mutants were evaluated. CONCLUSIONS The identification of ivi genes in V. anguillarum M3 sheds light on understanding the bacterial pathogenesis and provides novel targets for the development of new vaccines and diagnostic reagents. SIGNIFICANCE AND IMPACT OF THE STUDY To the best of our knowledge, this is the first report describing in vivo-expressed genes of V. anguillarum using IVIAT. The screened ivi genes in this study could be new virulent factors and targets for the development of vaccine, which may have implications for the development of diagnostic regents.
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Affiliation(s)
- Y-X Zou
- Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
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45
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Le Roux F, Labreuche Y, Davis BM, Iqbal N, Mangenot S, Goarant C, Mazel D, Waldor MK. Virulence of an emerging pathogenic lineage of Vibrio nigripulchritudo is dependent on two plasmids. Environ Microbiol 2010; 13:296-306. [PMID: 20825454 PMCID: PMC3020234 DOI: 10.1111/j.1462-2920.2010.02329.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Vibrioses are the predominant bacterial infections in marine shrimp farms. Vibrio nigripulchritudo is an emerging pathogen of the cultured shrimp Litopenaeus stylirostris in New Caledonia and other regions in the Indo-Pacific. The molecular determinants of V. nigripulchritudo pathogenicity are unknown; however, molecular epidemiological studies have revealed that recent pathogenic V. nigripulchritudo isolates from New Caledonia all cluster into a monophyletic clade and contain a small plasmid, pB1067. Here, we report that a large plasmid, pA1066 (247 kb), can also serve as a marker for virulent V. nigripulchritudo, and that an ancestral version of this plasmid was likely acquired prior to other virulence-linked markers. Additionally, we demonstrate that pA1066 is critical for the full virulence of V. nigripulchritudo in several newly developed experimental models of infection. Plasmid pB1067 also contributes to virulence; only strains containing both plasmids induced the highest level of shrimp mortality. Thus, it appears that these plasmids, which are absent from non-pathogenic isolates, may be driving forces, as well as markers, for the emergence of a pathogenic lineage of V. nigripulchritudo.
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Affiliation(s)
- Frédérique Le Roux
- Laboratoire de Génétique et Pathologie, IFREMER, 3790 La Tremblade, France.
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46
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In-depth analysis of exoproteomes from marine bacteria by shotgun liquid chromatography-tandem mass spectrometry: the Ruegeria pomeroyi DSS-3 case-study. Mar Drugs 2010; 8:2223-39. [PMID: 20948905 PMCID: PMC2953401 DOI: 10.3390/md8082223] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2010] [Revised: 07/27/2010] [Accepted: 07/28/2010] [Indexed: 12/16/2022] Open
Abstract
Microorganisms secrete into their extracellular environment numerous compounds that are required for their survival. Many of these compounds could be of great interest for biotechnology applications and their genes used in synthetic biology design. The secreted proteins and the components of the translocation systems themselves can be scrutinized in-depth by the most recent proteomic tools. While the secretomes of pathogens are well-documented, those of non-pathogens remain largely to be established. Here, we present the analysis of the exoproteome from the marine bacterium Ruegeria pomeroyi DSS-3 grown in standard laboratory conditions. We used a shotgun approach consisting of trypsin digestion of the exoproteome, and identification of the resulting peptides by liquid chromatography coupled to tandem mass spectrometry. Three different proteins that have domains homologous to those observed in RTX toxins were uncovered and were semi-quantified as the most abundantly secreted proteins. One of these proteins clearly stands out from the catalogue, representing over half of the total exoproteome. We also listed many soluble proteins related to ABC and TRAP transporters implied in the uptake of nutrients. The Ruegeria pomeroyi DSS-3 case-study illustrates the power of the shotgun nano-LC-MS/MS strategy to decipher the exoproteome from marine bacteria and to contribute to environmental proteomics.
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Abstract
Large bacterial protein toxins autotranslocate functional effector domains to the eukaryotic cell cytosol, resulting in alterations to cellular functions that ultimately benefit the infecting pathogen. Among these toxins, the clostridial glucosylating toxins (CGTs) produced by Gram-positive bacteria and the multifunctional-autoprocessing RTX (MARTX) toxins of Gram-negative bacteria have distinct mechanisms for effector translocation, but a shared mechanism of post-translocation autoprocessing that releases these functional domains from the large holotoxins. These toxins carry an embedded cysteine protease domain (CPD) that is activated for autoprocessing by binding inositol hexakisphosphate (InsP6), a molecule found exclusively in eukaryotic cells. Thus, InsP6-induced autoprocessing represents a unique mechanism for toxin effector delivery specifically within the target cell. This review summarizes recent studies of the structural and molecular events for activation of autoprocessing for both CGT and MARTX toxins, demonstrating both similar and potentially distinct aspects of autoprocessing among the toxins that utilize this method of activation and effector delivery.
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Shen A. Autoproteolytic activation of bacterial toxins. Toxins (Basel) 2010; 2:963-77. [PMID: 22069620 PMCID: PMC3153235 DOI: 10.3390/toxins2050963] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2010] [Revised: 04/28/2010] [Accepted: 05/05/2010] [Indexed: 01/05/2023] Open
Abstract
Protease domains within toxins typically act as the primary effector domain within target cells. By contrast, the primary function of the cysteine protease domain (CPD) in Multifunctional Autoprocessing RTX-like (MARTX) and Clostridium sp. glucosylating toxin families is to proteolytically cleave the toxin and release its cognate effector domains. The CPD becomes activated upon binding to the eukaryotic-specific small molecule, inositol hexakisphosphate (InsP6), which is found abundantly in the eukaryotic cytosol. This property allows the CPD to spatially and temporally regulate toxin activation, making it a prime candidate for developing anti-toxin therapeutics. In this review, we summarize recent findings related to defining the regulation of toxin function by the CPD and the development of inhibitors to prevent CPD-mediated activation of bacterial toxins.
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Affiliation(s)
- Aimee Shen
- Department of Pathology, Stanford School of Medicine, 300 Pasteur Drive, Stanford, California, USA.
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Mechanistic and structural insights into the proteolytic activation of Vibrio cholerae MARTX toxin. Nat Chem Biol 2009; 5:469-78. [PMID: 19465933 PMCID: PMC2783333 DOI: 10.1038/nchembio.178] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2008] [Accepted: 03/25/2009] [Indexed: 12/11/2022]
Abstract
MARTX toxins modulate the virulence of a number of Gram-negative Vibrio species. This family of toxins is defined by the presence of a cysteine protease domain (CPD), which proteolytically activates the Vibrio cholerae MARTX toxin. Although recent structural studies of the CPD have uncovered a novel allosteric activation mechanism, the mechanism of CPD substrate recognition or toxin processing is unknown. Here, we show that interdomain cleavage of MARTXVc enhances effector domain function. We also identify the first small molecule inhibitors of this protease domain and present the 2.35 Å structure of the CPD bound to one of these inhibitors. This structure, coupled with biochemical and mutational studies of the toxin, reveals the molecular basis of CPD substrate specificity and underscores the evolutionary relationship between the CPD and the clan CD caspase proteases. These studies are likely to prove valuable for devising novel anti-toxin strategies for a number of bacterial pathogens.
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Ma L, Chen J, Liu R, Zhang XH, Jiang YA. Mutation ofrpoS gene decreased resistance to environmental stresses, synthesis of extracellular products and virulence ofVibrio anguillarum. FEMS Microbiol Ecol 2009; 70:130-6. [DOI: 10.1111/j.1574-6941.2009.00713.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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