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Oscarsson J, Bao K, Shiratsuchi A, Grossmann J, Wolski W, Aung KM, Lindholm M, Johansson A, Mowsumi FR, Wai SN, Belibasakis GN, Bostanci N. Bacterial symbionts in oral niche use type VI secretion nanomachinery for fitness increase against pathobionts. iScience 2024; 27:109650. [PMID: 38650989 PMCID: PMC11033201 DOI: 10.1016/j.isci.2024.109650] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2023] [Revised: 02/09/2024] [Accepted: 03/27/2024] [Indexed: 04/25/2024] Open
Abstract
Microbial ecosystems experience spatial and nutrient restrictions leading to the coevolution of cooperation and competition among cohabiting species. To increase their fitness for survival, bacteria exploit machinery to antagonizing rival species upon close contact. As such, the bacterial type VI secretion system (T6SS) nanomachinery, typically expressed by pathobionts, can transport proteins directly into eukaryotic or prokaryotic cells, consequently killing cohabiting competitors. Here, we demonstrate for the first time that oral symbiont Aggregatibacter aphrophilus possesses a T6SS and can eliminate its close relative oral pathobiont Aggregatibacter actinomycetemcomitans using its T6SS. These findings bring nearer the anti-bacterial prospects of symbionts against cohabiting pathobionts while introducing the presence of an active T6SS in the oral cavity.
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Affiliation(s)
- Jan Oscarsson
- Oral Microbiology, Department of Odontology, Umeå University, Umeå, Sweden
| | - Kai Bao
- Division of Oral Health and Periodontology, Department of Dental Medicine, Karolinska Institutet, Alfred Nobels Allé 8, 14104 Huddinge, Stockholm, Sweden
| | - Akiko Shiratsuchi
- Department of Liberal Arts and Sciences, Graduate School of Medicine, Sapporo Medical University, Sapporo, Hokkaido 060-8556, Japan
| | - Jonas Grossmann
- Functional Genomics Center Zurich, ETH Zürich and University of Zürich, Zürich, Switzerland
- Swiss Institute of Bioinformatics (SIB) Quartier Sorge-Batiment Amphipole, 1015 Lausanne, Switzerland
| | - Witold Wolski
- Functional Genomics Center Zurich, ETH Zürich and University of Zürich, Zürich, Switzerland
- Swiss Institute of Bioinformatics (SIB) Quartier Sorge-Batiment Amphipole, 1015 Lausanne, Switzerland
| | - Kyaw Min Aung
- Department of Molecular Biology and the Umeå Centre for Microbial Research (UCMR), and the Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University, 90187 Umeå, Sweden
| | - Mark Lindholm
- Oral Microbiology, Department of Odontology, Umeå University, Umeå, Sweden
- Division of Oral Health and Periodontology, Department of Dental Medicine, Karolinska Institutet, Alfred Nobels Allé 8, 14104 Huddinge, Stockholm, Sweden
| | - Anders Johansson
- Oral Microbiology, Department of Odontology, Umeå University, Umeå, Sweden
| | | | - Sun Nyunt Wai
- Department of Molecular Biology and the Umeå Centre for Microbial Research (UCMR), and the Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University, 90187 Umeå, Sweden
| | - Georgios N. Belibasakis
- Division of Oral Health and Periodontology, Department of Dental Medicine, Karolinska Institutet, Alfred Nobels Allé 8, 14104 Huddinge, Stockholm, Sweden
| | - Nagihan Bostanci
- Division of Oral Health and Periodontology, Department of Dental Medicine, Karolinska Institutet, Alfred Nobels Allé 8, 14104 Huddinge, Stockholm, Sweden
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Yu Q, Li H, Du L, Shen L, Zhang J, Yuan L, Yao H, Xiao H, Bai Q, Jia Y, Qiu J, Li Y. Transcriptional regulation of the yersiniabactin receptor fyuA gene by the ferric uptake regulator in Klebsiella pneumoniae NTUH-K2044. J Basic Microbiol 2024:e202400001. [PMID: 38679904 DOI: 10.1002/jobm.202400001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2024] [Revised: 04/08/2024] [Accepted: 04/10/2024] [Indexed: 05/01/2024]
Abstract
The ferric uptake regulator (Fur) is a global regulator that influences the expression of virulence genes in Klebsiella pneumoniae. Bioinformatics analysis suggests Fur may involve in iron acquisition via the identified regulatory box upstream of the yersiniabactin receptor gene fyuA. To observe the impact of the gene fyuA on the virulence of K. pneumoniae, the gene fyuA knockout strain and complementation strain were constructed and then conducted a series of phenotypic experiments including chrome azurol S (CAS) detection, crystal violet staining, and wax moth virulence experiment. To examine the regulatory relationship between Fur and the gene fyuA, green fluorescent protein (GFP) reporter gene fusion assay, real-time quantitative reverse transcription polymerase chain reaction (RT-qPCR), gel migration assay (EMSA), and DNase I footprinting assay were used to clarify the regulatory mechanism of Fur on fyuA. CAS detection revealed that the gene fyuA could affect the generation of iron carriers in K. pneumoniae. Crystal violet staining experiment showed that fyuA could positively influence biofilm formation. Wax moth virulence experiment indicated that the deletion of the fyuA could weaken bacterial virulence. GFP reporter gene fusion experiment and RT-qPCR analysis revealed that Fur negatively regulated the expression of fyuA in iron-sufficient environment. EMSA experiment demonstrated that Fur could directly bind to the promoter region of fyuA, and DNase I footprinting assay further identified the specific binding site sequences. The study showed that Fur negatively regulated the transcriptional expression of fyuA by binding to upstream of the gene promoter region, and then affected the virulence of K. pneumoniae.
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Affiliation(s)
- Qian Yu
- School of Public Health, Chongqing Medical University, Chongqing, China
| | - Hailin Li
- School of Public Health, Chongqing Medical University, Chongqing, China
| | - Ling Du
- Chengdu Center for Disease Control and Prevention, Chengdu, Sichuan, China
| | - Lifei Shen
- Jiangbei District Center for Disease Control and Prevention, Jiangbei, Chongqing, China
| | - Jiaxue Zhang
- Jiangbei District Center for Disease Control and Prevention, Jiangbei, Chongqing, China
| | - Lingyue Yuan
- Shanghai Center for Disease Control and Prevention, Shanghai, China
| | - Huang Yao
- School of Public Health, Chongqing Medical University, Chongqing, China
| | - Hong Xiao
- School of Public Health, Chongqing Medical University, Chongqing, China
| | - Qunhua Bai
- School of Public Health, Chongqing Medical University, Chongqing, China
| | - Yan Jia
- School of Public Health, Chongqing Medical University, Chongqing, China
| | - Jingfu Qiu
- School of Public Health, Chongqing Medical University, Chongqing, China
| | - Yingli Li
- School of Public Health, Chongqing Medical University, Chongqing, China
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Mathieu-Denoncourt A, Duperthuy M. The VxrAB two-component system is important for the polymyxin B-dependent activation of the type VI secretion system in Vibrio cholerae O1 strain A1552. Can J Microbiol 2023; 69:393-406. [PMID: 37343290 DOI: 10.1139/cjm-2023-0026] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/23/2023]
Abstract
The type VI secretion system (T6SS) is used by bacteria for virulence, resistance to grazing, and competition with other bacteria. We previously demonstrated that the role of the T6SS in interbacterial competition and in resistance to grazing is enhanced in Vibrio cholerae in the presence of subinhibitory concentrations of polymyxin B. Here, we performed a global quantitative proteomic analysis and a targeted transcriptomic analysis of the T6SS-known regulators in V. cholerae grown with and without polymyxin B. The proteome of V. cholerae is greatly modified by polymyxin B with more than 39% of the identified cellular proteins displaying a difference in their abundance, including T6SS-related proteins. We identified a regulator whose abundance and expression are increased in the presence of polymyxin B, vxrB, the response regulator of the two-component system VxrAB (VCA0565-66). In vxrAB, vxrA and vxrB deficient mutants, the expression of both hcp copies (VC1415 and VCA0017), although globally reduced, was not modified by polymyxin B. These hcp genes encode an identical protein Hcp, which is the major component of the T6SS syringe. Thus, the upregulation of the T6SS in the presence of polymyxin B appears to be, at least in part, due to the two-component system VxrAB.
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Affiliation(s)
- Annabelle Mathieu-Denoncourt
- Département de Microbiologie, infectiologie et immunologie, Faculté de médecine, Université de Montréal, Montréal, QC, Canada
| | - Marylise Duperthuy
- Département de Microbiologie, infectiologie et immunologie, Faculté de médecine, Université de Montréal, Montréal, QC, Canada
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Hespanhol JT, Nóbrega-Silva L, Bayer-Santos E. Regulation of type VI secretion systems at the transcriptional, posttranscriptional and posttranslational level. Microbiology (Reading) 2023; 169:001376. [PMID: 37552221 PMCID: PMC10482370 DOI: 10.1099/mic.0.001376] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2023] [Accepted: 07/25/2023] [Indexed: 08/09/2023]
Abstract
Bacteria live in complex polymicrobial communities and are constantly competing for resources. The type VI secretion system (T6SS) is a widespread antagonistic mechanism used by Gram-negative bacteria to gain an advantage over competitors. T6SSs translocate toxic effector proteins inside target prokaryotic cells in a contact-dependent manner. In addition, some T6SS effectors can be secreted extracellularly and contribute to the scavenging scarce metal ions. Bacteria deploy their T6SSs in different situations, categorizing these systems into offensive, defensive and exploitative. The great variety of bacterial species and environments occupied by such species reflect the complexity of regulatory signals and networks that control the expression and activation of the T6SSs. Such regulation is tightly controlled at the transcriptional, posttranscriptional and posttranslational level by abiotic (e.g. pH, iron) or biotic (e.g. quorum-sensing) cues. In this review, we provide an update on the current knowledge about the regulatory networks that modulate the expression and activity of T6SSs across several species, focusing on systems used for interbacterial competition.
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Affiliation(s)
- Julia Takuno Hespanhol
- Department of Microbiology, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo 05508-900, Brazil
| | - Luize Nóbrega-Silva
- Department of Microbiology, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo 05508-900, Brazil
| | - Ethel Bayer-Santos
- Department of Microbiology, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo 05508-900, Brazil
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Krzyżanowska DM, Jabłońska M, Kaczyński Z, Czerwicka-Pach M, Macur K, Jafra S. Host-adaptive traits in the plant-colonizing Pseudomonas donghuensis P482 revealed by transcriptomic responses to exudates of tomato and maize. Sci Rep 2023; 13:9445. [PMID: 37296159 PMCID: PMC10256816 DOI: 10.1038/s41598-023-36494-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2023] [Accepted: 06/05/2023] [Indexed: 06/12/2023] Open
Abstract
Pseudomonads are metabolically flexible and can thrive on different plant hosts. However, the metabolic adaptations required for host promiscuity are unknown. Here, we addressed this knowledge gap by employing RNAseq and comparing transcriptomic responses of Pseudomonas donghuensis P482 to root exudates of two plant hosts: tomato and maize. Our main goal was to identify the differences and the common points between these two responses. Pathways upregulated only by tomato exudates included nitric oxide detoxification, repair of iron-sulfur clusters, respiration through the cyanide-insensitive cytochrome bd, and catabolism of amino and/or fatty acids. The first two indicate the presence of NO donors in the exudates of the test plants. Maize specifically induced the activity of MexE RND-type efflux pump and copper tolerance. Genes associated with motility were induced by maize but repressed by tomato. The shared response to exudates seemed to be affected both by compounds originating from the plants and those from their growth environment: arsenic resistance and bacterioferritin synthesis were upregulated, while sulfur assimilation, sensing of ferric citrate and/or other iron carriers, heme acquisition, and transport of polar amino acids were downregulated. Our results provide directions to explore mechanisms of host adaptation in plant-associated microorganisms.
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Affiliation(s)
- Dorota M Krzyżanowska
- Laboratory of Plant Microbiology, Intercollegiate Faculty of Biotechnology UG and MUG, University of Gdańsk, ul. A. Abrahama 58, 80-307, Gdańsk, Poland
| | - Magdalena Jabłońska
- Laboratory of Plant Microbiology, Intercollegiate Faculty of Biotechnology UG and MUG, University of Gdańsk, ul. A. Abrahama 58, 80-307, Gdańsk, Poland
| | - Zbigniew Kaczyński
- Laboratory of Structural Biochemistry, Faculty of Chemistry, University of Gdańsk, ul. Wita Stwosza 63, 80-308, Gdańsk, Poland
| | - Małgorzata Czerwicka-Pach
- Laboratory of Structural Biochemistry, Faculty of Chemistry, University of Gdańsk, ul. Wita Stwosza 63, 80-308, Gdańsk, Poland
| | - Katarzyna Macur
- Laboratory of Mass Spectrometry, Intercollegiate Faculty of Biotechnology UG and MUG, University of Gdańsk, ul. A. Abrahama 58, 80-307, Gdańsk, Poland
| | - Sylwia Jafra
- Laboratory of Plant Microbiology, Intercollegiate Faculty of Biotechnology UG and MUG, University of Gdańsk, ul. A. Abrahama 58, 80-307, Gdańsk, Poland.
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Proutière A, Drebes Dörr NC, Bader L, Stutzmann S, Metzger LC, Isaac S, Chiaruttini N, Blokesch M. Sporadic type VI secretion in seventh pandemic Vibrio cholerae. Microbiology (Reading) 2023; 169. [PMID: 37134007 DOI: 10.1099/mic.0.001329] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Vibrio cholerae is a pathogen that causes disease in millions of people every year by colonizing the small intestine and then secreting the potent cholera toxin. How the pathogen overcomes the colonization barrier created by the host's natural microbiota is, however, still not well understood. In this context, the type VI secretion system (T6SS) has gained considerable attention given its ability to mediate interbacterial killing. Interestingly, and in contrast to non-pandemic or environmental V. cholerae isolates, strains that are causing the ongoing cholera pandemic (7PET clade) are considered T6SS-silent under laboratory conditions. Since this idea was recently challenged, we performed a comparative in vitro study on T6SS activity using diverse strains or regulatory mutants. We show that modest T6SS activity is detectable in most of the tested strains under interbacterial competition conditions. The system's activity was also observed through immunodetection of the T6SS tube protein Hcp in culture supernatants, a phenotype that can be masked by the strains' haemagglutinin/protease. We further investigated the low T6SS activity within the bacterial populations by imaging 7PET V. cholerae at the single-cell level. The micrographs showed the production of the machinery in only a small fraction of cells within the population. This sporadic T6SS production was higher at 30 °C than at 37 °C and occurred independently of the known regulators TfoX and TfoY but was dependent on the VxrAB two-component system. Overall, our work provides new insight into the heterogeneity of T6SS production in populations of 7PET V. cholerae strains in vitro and provides a possible explanation of the system's low activity in bulk measurements.
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Affiliation(s)
- Alexis Proutière
- Laboratory of Molecular Microbiology, Global Health Institute, School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Natália C Drebes Dörr
- Laboratory of Molecular Microbiology, Global Health Institute, School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Loriane Bader
- Laboratory of Molecular Microbiology, Global Health Institute, School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Sandrine Stutzmann
- Laboratory of Molecular Microbiology, Global Health Institute, School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Lisa C Metzger
- Laboratory of Molecular Microbiology, Global Health Institute, School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Sandrine Isaac
- Laboratory of Molecular Microbiology, Global Health Institute, School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Nicolas Chiaruttini
- Bioimaging and Optics Platform (PT-BIOP), School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Melanie Blokesch
- Laboratory of Molecular Microbiology, Global Health Institute, School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
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Singh RP, Kumari K. Bacterial type VI secretion system (T6SS): an evolved molecular weapon with diverse functionality. Biotechnol Lett 2023; 45:309-331. [PMID: 36683130 DOI: 10.1007/s10529-023-03354-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2022] [Revised: 12/14/2022] [Accepted: 01/05/2023] [Indexed: 01/24/2023]
Abstract
Bacterial secretion systems are nanomolecular complexes that release a diverse set of virulence factors/or proteins into its surrounding or translocate to their target host cells. Among these systems, type VI secretion system 'T6SS' is a recently discovered molecular secretion system which is widely distributed in Gram-negative (-ve) bacteria, and shares structural similarity with the puncturing device of bacteriophages. The presence of T6SS is an advantage to many bacteria as it delivers toxins to its neighbour pathogens for competitive survival, and also translocates protein effectors to the host cells, leading to disruption of lipid membranes, cell walls, and cytoskeletons etc. Recent studies have characterized both anti-prokaryotic and anti-eukaryotic effectors, where T6SS is involved in diverse cellular functions including favouring colonization, enhancing the survival, adhesive modifications, internalization, and evasion of the immune system. With the evolution of advanced genomics and proteomics tools, there has been an increase in the number of characterized T6SS effector arsenals and also more clear information about the adaptive significance of this complex system. The functions of T6SS are generally regulated at the transcription, post-transcription and post-translational levels through diverse mechanisms. In the present review, we aimed to provide information about the distribution of T6SS in diverse bacteria, any structural similarity/or dissimilarity, effectors proteins, functional significance, and regulatory mechanisms. We also tried to provide information about the diverse roles played by T6SS in its natural environments and hosts, and further any changes in the microbiome.
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Affiliation(s)
- Rajnish Prakash Singh
- Department of Bioengineering and Biotechnology, Birla Institute of Technology, Mesra, Ranchi, Jharkhand, 835215, India.
| | - Kiran Kumari
- Department of Bioengineering and Biotechnology, Birla Institute of Technology, Mesra, Ranchi, Jharkhand, 835215, India
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Santoriello F, Pukatzki S. Type VI Secretion Systems: Environmental and Intra-host Competition of Vibrio cholerae. Adv Exp Med Biol 2023; 1404:41-63. [PMID: 36792870 DOI: 10.1007/978-3-031-22997-8_3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/17/2023]
Abstract
The Vibrio Type VI Secretion System (T6SS) is a harpoon-like nanomachine that serves as a defense system and is encoded by approximately 25% of all gram-negative bacteria. In this chapter, we describe the structure of the T6SS in different Vibrio species and outline how the use of different T6SS effector and immunity proteins control kin selection. We summarize the genetic loci that encode the structural elements that make up the Vibrio T6SSs and how these gene clusters are regulated. Finally, we provide insights into T6SS-based competitive dynamics, the role of T6SS genetic exchange in those competitive dynamics, and roles for the Vibrio T6SS in virulence.
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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Gallegos-Monterrosa R, Coulthurst SJ. The ecological impact of a bacterial weapon: microbial interactions and the Type VI secretion system. FEMS Microbiol Rev 2021; 45:fuab033. [PMID: 34156081 PMCID: PMC8632748 DOI: 10.1093/femsre/fuab033] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2021] [Accepted: 06/20/2021] [Indexed: 12/13/2022] Open
Abstract
Bacteria inhabit all known ecological niches and establish interactions with organisms from all kingdoms of life. These interactions are mediated by a wide variety of mechanisms and very often involve the secretion of diverse molecules from the bacterial cells. The Type VI secretion system (T6SS) is a bacterial protein secretion system that uses a bacteriophage-like machinery to secrete a diverse array of effectors, usually translocating them directly into neighbouring cells. These effectors display toxic activity in the recipient cell, making the T6SS an effective weapon during inter-bacterial competition and interactions with eukaryotic cells. Over the last two decades, microbiology research has experienced a shift towards using systems-based approaches to study the interactions between diverse organisms and their communities in an ecological context. Here, we focus on this aspect of the T6SS. We consider how our perspective of the T6SS has developed and examine what is currently known about the impact that bacteria deploying the T6SS can have in diverse environments, including niches associated with plants, insects and mammals. We consider how T6SS-mediated interactions can affect host organisms by shaping their microbiota, as well as the diverse interactions that can be established between different microorganisms through the deployment of this versatile secretion system.
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Affiliation(s)
| | - Sarah J Coulthurst
- School of Life Sciences, University of Dundee, Dow Street, Dundee DD1 5EH, UK
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Mathieu-Denoncourt A, Duperthuy M. Secretome analysis reveals a role of subinhibitory concentrations of polymyxin B in the survival of Vibrio cholerae mediated by the type VI secretion system. Environ Microbiol 2021; 24:1133-1149. [PMID: 34490971 DOI: 10.1111/1462-2920.15762] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2021] [Accepted: 09/04/2021] [Indexed: 11/30/2022]
Abstract
Antimicrobials are commonly used in prevention of infections including in aquaculture, agriculture and medicine. Subinhibitory concentrations of antimicrobial peptides can modulate resistance, virulence and persistence effectors in Gram-negative pathogens. In this study, we investigated the effect of subinhibitory concentrations of polymyxin B (PmB) on the secretome of Vibrio cholerae, a natural inhabitant of aquatic environments and the pathogen responsible for the cholera disease. Our proteomic approach revealed that the abundance of many extracellular proteins is affected by PmB and some of them are detected only either in the presence or in the absence of PmB. The type VI secretion system (T6SS) secreted hemolysin-coregulated protein (Hcp) displayed an increased abundance in the presence of PmB. Hcp is also more abundant in the bacterial cells in the presence of PmB and hcp expression is upregulated upon PmB supplementation. No effect of the T6SS on antimicrobial resistance was observed. Conversely, PmB increases the T6SS-dependent cytotoxicity of V. cholerae towards the amoeba Dictyostelium discoideum and its ability to compete with Escherichia coli.
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Affiliation(s)
- Annabelle Mathieu-Denoncourt
- Department de Microbiologie, infectiologie et immunologie, Faculté de Médecine, Université de Montreal, Montreal, Quebec, H3T 1J4, Canada
| | - Marylise Duperthuy
- Department de Microbiologie, infectiologie et immunologie, Faculté de Médecine, Université de Montreal, Montreal, Quebec, H3T 1J4, Canada
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Abstract
Many bacterial species employ systems for interference competition with other microorganisms. Some systems are effective without contact (e.g., through secretion of toxins), while other systems (e.g., type VI secretion system [T6SS]) require direct contact between cells. Here, we provide the initial characterization of a novel contact-dependent competition system for Proteus mirabilis. In neonatal mice, a commensal P. mirabilis strain apparently eliminated commensal Escherichia coli. We replicated the phenotype in vitro and showed that P. mirabilis efficiently reduced the viability of several Enterobacteriaceae species but not Gram-positive species or yeast cells. Importantly, P. mirabilis strains isolated from humans also killed E. coli. A reduction of viability occurred from early stationary phase to 24 h of culture and was observed in shaking liquid media as well as on solid media. Killing required contact but was independent of T6SS, which is the only contact-dependent killing system described for P. mirabilis. Expression of the killing system was regulated by osmolarity and components secreted into the supernatant. Stationary-phase P. mirabilis culture supernatant itself did not kill but was sufficient to induce killing in an exponentially growing coculture. In contrast, killing was largely prevented in media with low osmolarity. In summary, we provide the initial characterization of a potentially novel interbacterial competition system used by P. mirabilis. IMPORTANCE The study of bacterial competition systems has received significant attention in recent years. These systems are important in a multitude of polymicrobial environments and collectively shape the composition of complex ecosystems like the mammalian gut. They are also being explored as narrow-spectrum alternatives to specifically eliminate problematic pathogenic species. However, only a small fraction of the estimated number of interbacterial competition systems has been identified. We discovered a competition system that is novel for Proteus mirabilis. Inspired by an observation in infant mice, we confirmed in vitro that P. mirabilis was able to efficiently kill several Enterobacteriaceae species. This killing system might represent a new function of a known competition system or even a novel system, as the observed characteristics do not fit with described contact-dependent competition systems. Further characterization of this system might help understand how P. mirabilis competes with other Enterobacteriaceae in various niches.
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13
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Manera K, Caro F, Li H, Pei TT, Hersch SJ, Mekalanos JJ, Dong TG. Sensing of intracellular Hcp levels controls T6SS expression in Vibrio cholerae. Proc Natl Acad Sci U S A 2021; 118:e2104813118. [PMID: 34161288 DOI: 10.1073/pnas.2104813118] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The type 6 secretion system (T6SS) is a bacterial weapon broadly distributed in gram-negative bacteria and used to kill competitors and predators. Featuring a long and double-tubular structure, this molecular machine is energetically costly to produce and thus is likely subject to diverse regulation strategies that are largely ill defined. In this study, we report a quantity-sensing control of the T6SS that down-regulates the expression of secreted components when they accumulate in the cytosol due to T6SS inactivation. Using Vibrio cholerae strains that constitutively express an active T6SS, we demonstrate that mRNA levels of secreted components, including the inner-tube protein component Hcp, were down-regulated in T6SS structural gene mutants while expression of the main structural genes remained unchanged. Deletion of both hcp gene copies restored expression from their promoters, while Hcp overexpression negatively impacted expression. We show that Hcp directly interacts with the RpoN-dependent T6SS regulator VasH, and deleting the N-terminal regulator domain of VasH abolishes this interaction as well as the expression difference of hcp operons between T6SS-active and inactive strains. We find that negative regulation of hcp also occurs in other V. cholerae strains and the pathogens Aeromonas dhakensis and Pseudomonas aeruginosa This Hcp-dependent sensing control is likely an important energy-conserving mechanism that enables T6SS-encoding organisms to quickly adjust T6SS expression and prevent wasteful build-up of its major secreted components in the absence of their efficient export out of the bacterial cell.
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14
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Zhang A, Han Y, Huang Y, Hu X, Liu P, Liu X, Kan B, Liang W. vgrG is separately transcribed from hcp in T6SS orphan clusters and is under the regulation of IHF and HapR. Biochem Biophys Res Commun 2021; 559:15-20. [PMID: 33932896 DOI: 10.1016/j.bbrc.2021.04.092] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2021] [Accepted: 04/21/2021] [Indexed: 11/29/2022]
Abstract
V. cholerae, the causative agent of cholera epidemic, and V. fluvialis, the emerging foodborne pathogen, share highly homologous T6SS consisting of one large cluster and two small orphan or auxiliary clusters, and each of which was generally recognized as one operon. Here, we showed that the genes in each of the small clusters are organized into two transcriptional units. Specifically, the inner tube coding gene hcp/tssD is highly transcribed as one monocistron, while the tip component vgrG/tssI and its downstream effector and immunity genes are in one polycistron with very low transcriptional level. This conclusion is supported by qPCR analysis of mRNA abundance, reporter fusion analysis and transcriptional unit definition with RT-PCR analysis. Taking tssI2_a of V. fluvialis as an example, we further demonstrated that quorum sensing (QS) regulator HapR and global regulator IHF activate vgrG/tssI transcription by directly binding to its promoter region. Taken together, current studies deepen our understanding of T6SS system, highlighting its regulatory complexity during functional execution process.
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Affiliation(s)
- Anran Zhang
- State Key Laboratory of Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Changbai Road 155, Changping District, Beijing, China
| | - Yu Han
- State Key Laboratory of Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Changbai Road 155, Changping District, Beijing, China
| | - Yuanming Huang
- State Key Laboratory of Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Changbai Road 155, Changping District, Beijing, China
| | - Xiao Hu
- State Key Laboratory of Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Changbai Road 155, Changping District, Beijing, China
| | - Ping Liu
- State Key Laboratory of Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Changbai Road 155, Changping District, Beijing, China
| | - Xiaoshu Liu
- State Key Laboratory of Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Changbai Road 155, Changping District, Beijing, China
| | - Biao Kan
- State Key Laboratory of Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Changbai Road 155, Changping District, Beijing, China.
| | - Weili Liang
- State Key Laboratory of Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Changbai Road 155, Changping District, Beijing, China.
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15
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Myint SL, Zlatkov N, Aung KM, Toh E, Sjöström A, Nadeem A, Duperthuy M, Uhlin BE, Wai SN. Ecotin and LamB in Escherichia coli influence the susceptibility to Type VI secretion-mediated interbacterial competition and killing by Vibrio cholerae. Biochim Biophys Acta Gen Subj 2021; 1865:129912. [PMID: 33892013 DOI: 10.1016/j.bbagen.2021.129912] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2020] [Revised: 04/11/2021] [Accepted: 04/12/2021] [Indexed: 01/04/2023]
Abstract
BACKGROUND A prevailing action of the Type VI secretion system (T6SS) in several Gram-negative bacterial species is inter-bacterial competition. In the past several years, many effectors of T6SS were identified in different bacterial species and their involvement in inter-bacterial interactions were described. However, possible defence mechanisms against T6SS attack among prey bacteria were not well clarified yet. METHODS Escherichia coli was assessed for susceptibility to T6SS-mediated killing by Vibrio cholerae. TheT6SS-mediated bacterial killing assays were performed in absence or presence of different protease inhibitors and with different mutant E. coli strains. Expression levels of selected proteins were monitored using SDS-PAGE and immunoblot analyses. RESULTS The T6SS-mediated killing of E. coli by V. cholerae was partly blocked when the serine protease inhibitor Pefabloc was present. E. coli lacking the periplasmic protease inhibitor Ecotin showed enhanced susceptibility to killing by V. cholerae. Mutations affecting E. coli membrane stability also caused increased susceptibility to killing by V. cholerae. E. coli lacking the maltodextrin porin protein LamB showed reduced susceptibility to killing by V. cholerae whereas E. coli with induced high levels of LamB showed reduced survival in inter-bacterial competition. CONCLUSIONS Our study identified two proteins in E. coli, the intrinsic protease inhibitor Ecotin and the outer membrane porin LamB, that influenced E. coli susceptibility to T6SS-mediated killing by V. cholerae. GENERAL SIGNIFICANCE We envision that it is feasible to explore these findings to target and modulate their expression to obtain desired changes in inter-bacterial competition in vivo, e.g. in the gastrointestinal microbiome.
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Affiliation(s)
- Si Lhyam Myint
- Department of Molecular Biology, The Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå Centre for Microbial Research (UCMR), Umeå University, Umeå, Sweden
| | - Nikola Zlatkov
- Department of Molecular Biology, The Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå Centre for Microbial Research (UCMR), Umeå University, Umeå, Sweden
| | - Kyaw Min Aung
- Department of Molecular Biology, The Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå Centre for Microbial Research (UCMR), Umeå University, Umeå, Sweden
| | - Eric Toh
- Department of Molecular Biology, The Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå Centre for Microbial Research (UCMR), Umeå University, Umeå, Sweden
| | - Annika Sjöström
- Department of Molecular Biology, The Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå Centre for Microbial Research (UCMR), Umeå University, Umeå, Sweden
| | - Aftab Nadeem
- Department of Molecular Biology, The Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå Centre for Microbial Research (UCMR), Umeå University, Umeå, Sweden
| | - Marylise Duperthuy
- Department of Molecular Biology, The Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå Centre for Microbial Research (UCMR), Umeå University, Umeå, Sweden; Département de Microbiologie, Infectiologie et Immunologie, Université de Montréal, Succ. Centre-ville, Montréal, Québec, Canada.
| | - Bernt Eric Uhlin
- Department of Molecular Biology, The Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå Centre for Microbial Research (UCMR), Umeå University, Umeå, Sweden.
| | - Sun Nyunt Wai
- Department of Molecular Biology, The Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå Centre for Microbial Research (UCMR), Umeå University, Umeå, Sweden.
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16
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Liu X, Pan J, Gao H, Han Y, Zhang A, Huang Y, Liu P, Kan B, Liang W. CqsA/LuxS-HapR Quorum sensing circuit modulates type VI secretion system VflT6SS2 in Vibrio fluvialis. Emerg Microbes Infect 2021; 10:589-601. [PMID: 33689580 PMCID: PMC8018390 DOI: 10.1080/22221751.2021.1902244] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Vibrio fluvialis is an emerging enteric pathogen of increasing public health threat. Two quorum sensing (QS) systems, VfqI-VfqR and CqsA/LuxS-HapR, and two type VI secretion systems (T6SSs), VflT6SS1 and VflT6SS2, have been identified in V. fluvialis. Whether there exists any correlation between the two systems is unclear. In this study, we found that CqsA/LuxS-HapR circuit regulator LuxO represses while HapR activates VflT6SS2. The effect of LuxO is more pronounced at low cell density and is HapR-dependent. Deletion of hapR abolished Hcp expression and alleviated antibacterial virulence. However, these effects were rescued by HapR-expressing plasmid. Reporter fusion analyses showed that HapR is required for the promoter activities of VflT6SS2. Sequence inspection of the major cluster promoter revealed two potential Motif 1 HapR binding sites, and their bindings to HapR were confirmed by both electrophoretic mobility shift assay (EMSA) and DNase I footprinting assay. Meanwhile, two single Motif 2 sites were identified in tssD2_a (hcpA) and tssD2_b (hcpB) promoter regions of the orphan cluster which are less conserved and displayed lower affinities to HapR. Together, our study demonstrated that CqsA/LuxS-HapR QS manipulate VflT6SS2 in V. fluvialis, and this finding will enhance our understanding of possible crosstalk between T6SS and QS in microbes.
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Affiliation(s)
- Xiaoshu Liu
- State Key Laboratory for Infectious Disease Prevention and Control, Chinese Center for Disease Control and Prevention, National Institute for Communicable Disease Control and Prevention, Beijing, People's Republic of China
| | - Jingjing Pan
- State Key Laboratory for Infectious Disease Prevention and Control, Chinese Center for Disease Control and Prevention, National Institute for Communicable Disease Control and Prevention, Beijing, People's Republic of China
| | - He Gao
- State Key Laboratory for Infectious Disease Prevention and Control, Chinese Center for Disease Control and Prevention, National Institute for Communicable Disease Control and Prevention, Beijing, People's Republic of China
| | - Yu Han
- State Key Laboratory for Infectious Disease Prevention and Control, Chinese Center for Disease Control and Prevention, National Institute for Communicable Disease Control and Prevention, Beijing, People's Republic of China
| | - Anran Zhang
- State Key Laboratory for Infectious Disease Prevention and Control, Chinese Center for Disease Control and Prevention, National Institute for Communicable Disease Control and Prevention, Beijing, People's Republic of China
| | - Yuanming Huang
- State Key Laboratory for Infectious Disease Prevention and Control, Chinese Center for Disease Control and Prevention, National Institute for Communicable Disease Control and Prevention, Beijing, People's Republic of China
| | - Ping Liu
- State Key Laboratory for Infectious Disease Prevention and Control, Chinese Center for Disease Control and Prevention, National Institute for Communicable Disease Control and Prevention, Beijing, People's Republic of China
| | - Biao Kan
- State Key Laboratory for Infectious Disease Prevention and Control, Chinese Center for Disease Control and Prevention, National Institute for Communicable Disease Control and Prevention, Beijing, People's Republic of China
| | - Weili Liang
- State Key Laboratory for Infectious Disease Prevention and Control, Chinese Center for Disease Control and Prevention, National Institute for Communicable Disease Control and Prevention, Beijing, People's Republic of China
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17
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Abstract
The bacterium Vibrio cholerae is the etiologic agent of the severe human diarrheal disease cholera. The gut microbiome, or the native community of microorganisms found in the human gastrointestinal tract, is increasingly being recognized as a factor in driving susceptibility to infection, in vivo fitness, and host interactions of this pathogen. Here, we review a subset of the emerging studies in how gut microbiome structure and microbial function are able to drive V. cholerae virulence gene regulation, metabolism, and modulate host immune responses to cholera infection and vaccination. Improved mechanistic understanding of commensal-pathogen interactions offers new perspectives in the design of prophylactic and therapeutic approaches for cholera control.
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Affiliation(s)
- Jennifer Y. Cho
- Department of Microbiology and Plant Pathology, University of California, Riverside, CA, USA
- Department of Biochemistry, University of California, Riverside, California, USA
| | - Rui Liu
- Department of Microbiology and Plant Pathology, University of California, Riverside, CA, USA
- Graduate Program in Genetics, Genomics, and Bioinformatics, University of California, Riverside, California, USA
| | - John C. Macbeth
- Department of Microbiology and Plant Pathology, University of California, Riverside, CA, USA
- Division of Biomedical Sciences, School of Medicine, University of California, Riverside, California, USA
| | - Ansel Hsiao
- Department of Microbiology and Plant Pathology, University of California, Riverside, CA, USA
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18
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Hug S, Liu Y, Heiniger B, Bailly A, Ahrens CH, Eberl L, Pessi G. Differential Expression of Paraburkholderia phymatum Type VI Secretion Systems (T6SS) Suggests a Role of T6SS-b in Early Symbiotic Interaction. Front Plant Sci 2021; 12:699590. [PMID: 34394152 PMCID: PMC8356804 DOI: 10.3389/fpls.2021.699590] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/2021] [Accepted: 06/28/2021] [Indexed: 05/06/2023]
Abstract
Paraburkholderia phymatum STM815, a rhizobial strain of the Burkholderiaceae family, is able to nodulate a broad range of legumes including the agriculturally important Phaseolus vulgaris (common bean). P. phymatum harbors two type VI Secretion Systems (T6SS-b and T6SS-3) in its genome that contribute to its high interbacterial competitiveness in vitro and in infecting the roots of several legumes. In this study, we show that P. phymatum T6SS-b is found in the genomes of several soil-dwelling plant symbionts and that its expression is induced by the presence of citrate and is higher at 20/28°C compared to 37°C. Conversely, T6SS-3 shows homologies to T6SS clusters found in several pathogenic Burkholderia strains, is more prominently expressed with succinate during stationary phase and at 37°C. In addition, T6SS-b expression was activated in the presence of germinated seeds as well as in P. vulgaris and Mimosa pudica root nodules. Phenotypic analysis of selected deletion mutant strains suggested a role of T6SS-b in motility but not at later stages of the interaction with legumes. In contrast, the T6SS-3 mutant was not affected in any of the free-living and symbiotic phenotypes examined. Thus, P. phymatum T6SS-b is potentially important for the early infection step in the symbiosis with legumes.
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Affiliation(s)
- Sebastian Hug
- Department of Plant and Microbial Biology, University of Zurich, Zurich, Switzerland
| | - Yilei Liu
- Department of Plant and Microbial Biology, University of Zurich, Zurich, Switzerland
| | - Benjamin Heiniger
- Agroscope, Research Group Molecular Diagnostics, Genomics and Bioinformatics, Swiss Institute of Bioinformatics, Wädenswil, Switzerland
| | - Aurélien Bailly
- Department of Plant and Microbial Biology, University of Zurich, Zurich, Switzerland
| | - Christian H. Ahrens
- Agroscope, Research Group Molecular Diagnostics, Genomics and Bioinformatics, Swiss Institute of Bioinformatics, Wädenswil, Switzerland
| | - Leo Eberl
- Department of Plant and Microbial Biology, University of Zurich, Zurich, Switzerland
| | - Gabriella Pessi
- Department of Plant and Microbial Biology, University of Zurich, Zurich, Switzerland
- *Correspondence: Gabriella Pessi,
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19
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Mahmud AKMF, Nilsson K, Fahlgren A, Navais R, Choudhury R, Avican K, Fällman M. Genome-Scale Mapping Reveals Complex Regulatory Activities of RpoN in Yersinia pseudotuberculosis. mSystems 2020; 5:e01006-20. [PMID: 33172972 PMCID: PMC7657599 DOI: 10.1128/msystems.01006-20] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2020] [Accepted: 10/20/2020] [Indexed: 11/26/2022] Open
Abstract
RpoN, an alternative sigma factor commonly known as σ54, is implicated in persistent stages of Yersinia pseudotuberculosis infections in which genes associated with this regulator are upregulated. We here combined phenotypic and genomic assays to provide insight into its role and function in this pathogen. RpoN was found essential for Y. pseudotuberculosis virulence in mice, and in vitro functional assays showed that it controls biofilm formation and motility. Mapping genome-wide associations of Y. pseudotuberculosis RpoN using chromatin immunoprecipitation coupled with next-generation sequencing identified an RpoN binding motif located at 103 inter- and intragenic sites on both sense and antisense strands. Deletion of rpoN had a large impact on gene expression, including downregulation of genes encoding proteins involved in flagellar assembly, chemotaxis, and quorum sensing. There were also clear indications of cross talk with other sigma factors, together with indirect effects due to altered expression of other regulators. Matching differential gene expression with locations of the binding sites implicated around 130 genes or operons potentially activated or repressed by RpoN. Mutagenesis of selected intergenic binding sites confirmed both positive and negative regulatory effects of RpoN binding. Corresponding mutations of intragenic sense sites had less impact on associated gene expression. Surprisingly, mutating intragenic sites on the antisense strand commonly reduced expression of genes carried by the corresponding sense strand.IMPORTANCE The alternative sigma factor RpoN (σ54), which is widely distributed in eubacteria, has been implicated in controlling gene expression of importance for numerous functions including virulence. Proper responses to host environments are crucial for bacteria to establish infection, and regulatory mechanisms involved are therefore of high interest for development of future therapeutics. Little is known about the function of RpoN in the intestinal pathogen Y. pseudotuberculosis, and we therefore investigated its regulatory role in this pathogen. This regulator was indeed found to be critical for establishment of infection in mice, likely involving its requirement for motility and biofilm formation. The RpoN regulon involved both activating and suppressive effects on gene expression which could be confirmed with mutagenesis of identified binding sites. This is the first study of its kind of RpoN in Y. pseudotuberculosis, revealing complex regulation of gene expression involving both productive and silent effects of its binding to DNA, providing important information about RpoN regulation in enterobacteria.
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Affiliation(s)
- A K M Firoj Mahmud
- Department of Molecular Biology, Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå Centre for Microbial Research (UCMR), Umeå University, Umeå, Sweden
| | - Kristina Nilsson
- Department of Molecular Biology, Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå Centre for Microbial Research (UCMR), Umeå University, Umeå, Sweden
| | - Anna Fahlgren
- Department of Molecular Biology, Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå Centre for Microbial Research (UCMR), Umeå University, Umeå, Sweden
| | - Roberto Navais
- Department of Molecular Biology, Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå Centre for Microbial Research (UCMR), Umeå University, Umeå, Sweden
| | - Rajdeep Choudhury
- Department of Molecular Biology, Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå Centre for Microbial Research (UCMR), Umeå University, Umeå, Sweden
| | - Kemal Avican
- Department of Molecular Biology, Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå Centre for Microbial Research (UCMR), Umeå University, Umeå, Sweden
| | - Maria Fällman
- Department of Molecular Biology, Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå Centre for Microbial Research (UCMR), Umeå University, Umeå, Sweden
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20
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Seibt H, Aung KM, Ishikawa T, Sjöström A, Gullberg M, Atkinson GC, Wai SN, Shingler V. Elevated levels of VCA0117 (VasH) in response to external signals activate the type VI secretion system of Vibrio cholerae O1 El Tor A1552. Environ Microbiol 2020; 22:4409-4423. [PMID: 32592280 DOI: 10.1111/1462-2920.15141] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2019] [Revised: 06/22/2020] [Accepted: 06/23/2020] [Indexed: 11/29/2022]
Abstract
The type VI nanomachine is critical for Vibrio cholerae to establish infections and to thrive in niches co-occupied by competing bacteria. The genes for the type VI structural proteins are encoded in one large and two small auxiliary gene clusters. VCA0117 (VasH) - a σ54 -transcriptional activator - is strictly required for functionality of the type VI secretion system since it controls production of the structural protein Hcp. While some strains constitutively produce a functional system, others do not and require specific growth conditions of low temperature and high osmolarity for expression of the type VI machinery. Here, we trace integration of these regulatory signals to the promoter activity of the large gene cluster in which many components of the machinery and VCA0117 itself are encoded. Using in vivo and in vitro assays and variants of VCA0117, we show that activation of the σ54 -promoters of the auxiliary gene clusters by elevated VCA0117 levels are all that is required to overcome the need for specialized growth conditions. We propose a model in which signal integration via the large operon promoter directs otherwise restrictive levels of VCA0117 that ultimately dictates a sufficient supply of Hcp for completion of a functional type VI secretion system.
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Affiliation(s)
- Henrik Seibt
- Department of Molecular Biology, Umeå University, Umeå, SE-901 87, Sweden
| | - Kyaw Min Aung
- Department of Molecular Biology, Umeå University, Umeå, SE-901 87, Sweden.,Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University, Umeå, SE-901 87, Sweden
| | - Takahiko Ishikawa
- Department of Molecular Biology, Umeå University, Umeå, SE-901 87, Sweden.,Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University, Umeå, SE-901 87, Sweden
| | - Annika Sjöström
- Department of Molecular Biology, Umeå University, Umeå, SE-901 87, Sweden
| | - Martin Gullberg
- Department of Molecular Biology, Umeå University, Umeå, SE-901 87, Sweden
| | - Gemma Catherine Atkinson
- Department of Molecular Biology, Umeå University, Umeå, SE-901 87, Sweden.,Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University, Umeå, SE-901 87, Sweden
| | - Sun Nyunt Wai
- Department of Molecular Biology, Umeå University, Umeå, SE-901 87, Sweden.,Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University, Umeå, SE-901 87, Sweden
| | - Victoria Shingler
- Department of Molecular Biology, Umeå University, Umeå, SE-901 87, Sweden
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21
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Choi Y, Kim N, Mannaa M, Kim H, Park J, Jung H, Han G, Lee HH, Seo YS. Characterization of Type VI Secretion System in Xanthomonas oryzae pv. oryzae and Its Role in Virulence to Rice. Plant Pathol J 2020; 36:289-296. [PMID: 32547344 PMCID: PMC7272854 DOI: 10.5423/ppj.nt.02.2020.0026] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/07/2020] [Revised: 04/27/2020] [Accepted: 04/28/2020] [Indexed: 06/11/2023]
Abstract
Type VI secretion system (T6SS) is a contact-dependent secretion system, employed by most gram-negative bacteria for translocating effector proteins to target cells. The present study was conducted to investigate T6SS in Xanthomonas oryzae pv. oryzae (Xoo), which causes bacterial blight in rice, and to unveil its functions. Two T6SS clusters were found in the genome of Xoo PXO99A. The deletion mutants, Δhcp1, Δhcp2, and Δhcp12, targeting the hcp gene in each cluster, and a double-deletion mutant targeting both genes were constructed and tested for growth rate, pathogenicity to rice, and inter-bacterial competition ability. The results indicated that hcp in T6SS-2, but not T6SS-1, was involved in bacterial virulence to rice plants. However, neither T6SS-1 nor T6SS-2 had any effect on the ability to compete with Escherichia coli or other bacterial cells. In conclusion, T6SS gene clusters in Xoo have been characterized, and its role in virulence to rice was confirmed.
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Affiliation(s)
- Yeounju Choi
- Department of Integrated Biological Science, Pusan National University, Busan 46241, Korea
| | - Namgyu Kim
- Department of Integrated Biological Science, Pusan National University, Busan 46241, Korea
| | - Mohamed Mannaa
- Department of Integrated Biological Science, Pusan National University, Busan 46241, Korea
- Department of Plant Pathology, Cairo University, Giza 12613, Egypt
| | - Hongsup Kim
- Korea Seed & Variety Serv, Seed Testing & Res Ctr, Gimcheon 39660, Korea
| | - Jungwook Park
- Department of Integrated Biological Science, Pusan National University, Busan 46241, Korea
| | - Hyejung Jung
- Department of Integrated Biological Science, Pusan National University, Busan 46241, Korea
| | - Gil Han
- Department of Integrated Biological Science, Pusan National University, Busan 46241, Korea
| | - Hyun-Hee Lee
- Department of Integrated Biological Science, Pusan National University, Busan 46241, Korea
| | - Young-Su Seo
- Department of Integrated Biological Science, Pusan National University, Busan 46241, Korea
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Song H, Kang Y, Qian A, Shan X, Li Y, Zhang L, Zhang H, Sun W. Inactivation of the T6SS inner membrane protein DotU results in severe attenuation and decreased pathogenicity of Aeromonas veronii TH0426. BMC Microbiol 2020; 20:76. [PMID: 32245412 PMCID: PMC7119292 DOI: 10.1186/s12866-020-01743-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2019] [Accepted: 03/04/2020] [Indexed: 11/19/2022] Open
Abstract
Background The inner membrane protein DotU of Aeromonas veronii is an important component of the minimal core conserved membrane proteome required for the formation of an envelope-transmembrane complex. This protein functions in a type VI secretion system (T6SS), and the role of this T6SS during the pathogenic process has not been clearly described. Results A recombinant A. veronii with a partial disruption of the dotU gene (720 bp of the in-frame sequence) (defined as ∆dotU) was constructed by two conjugate exchanges. We found that the mutant ∆dotU allele can be stably inherited for more than 50 generations. Inactivation of the A. veronii dotU gene resulted in no significant changes in growth or resistance to various environmental changes. However, compared with the wild-type strain colony, the mutant ∆dotU colony had a rough surface morphology. In addition, the biofilm formation ability of the mutant ∆dotU was significantly enhanced by 2.1-fold. Conversely, the deletion of the dotU gene resulted in a significant decrease in pathogenicity and infectivity compared to those of the A. veronii wild-type strain. Conclusions Our findings indicated that the dotU gene was an essential participant in the pathogenicity and invasiveness of A. veronii TH0426, which provides a novel perspective on the pathogenesis of TH0426 and lays the foundation for discovering potential T6SS effectors.
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Affiliation(s)
- Haichao Song
- College of Animal Science and Technology, Jilin Agricultural University, Changchun, Jilin, 130118, China
| | - Yuanhuan Kang
- College of Animal Science and Technology, Jilin Agricultural University, Changchun, Jilin, 130118, China
| | - Aidong Qian
- College of Animal Science and Technology, Jilin Agricultural University, Changchun, Jilin, 130118, China
| | - Xiaofeng Shan
- College of Animal Science and Technology, Jilin Agricultural University, Changchun, Jilin, 130118, China
| | - Ying Li
- College of Animal Science and Technology, Jilin Agricultural University, Changchun, Jilin, 130118, China
| | - Lei Zhang
- College of Animal Science and Technology, Jilin Agricultural University, Changchun, Jilin, 130118, China
| | - Haipeng Zhang
- College of Animal Science and Technology, Jilin Agricultural University, Changchun, Jilin, 130118, China
| | - Wuwen Sun
- College of Animal Science and Technology, Jilin Agricultural University, Changchun, Jilin, 130118, China.
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Crisan CV, Hammer BK. The
Vibrio cholerae
type VI secretion system: toxins, regulators and consequences. Environ Microbiol 2020; 22:4112-4122. [DOI: 10.1111/1462-2920.14976] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2019] [Revised: 03/01/2020] [Accepted: 03/02/2020] [Indexed: 12/13/2022]
Affiliation(s)
- Cristian V. Crisan
- Center for Microbial Dynamics and Infection Georgia Institute of Technology Atlanta GA USA
- Institute for Bioengineering and Biosciences, Georgia Institute of Technology Atlanta GA USA
- School of Biological Sciences, Georgia Institute of Technology Atlanta GA USA
| | - Brian K. Hammer
- Center for Microbial Dynamics and Infection Georgia Institute of Technology Atlanta GA USA
- Institute for Bioengineering and Biosciences, Georgia Institute of Technology Atlanta GA USA
- School of Biological Sciences, Georgia Institute of Technology Atlanta GA USA
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Guckes KR, Cecere AG, Williams AL, McNeil AE, Miyashiro T. The Bacterial Enhancer Binding Protein VasH Promotes Expression of a Type VI Secretion System in Vibrio fischeri during Symbiosis. J Bacteriol 2020; 202:e00777-19. [PMID: 31964698 DOI: 10.1128/JB.00777-19] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Accepted: 01/13/2020] [Indexed: 11/20/2022] Open
Abstract
Vibrio fischeri is a bacterial symbiont that colonizes the light organ of the Hawaiian bobtail squid, Euprymna scolopes Certain strains of V. fischeri express a type VI secretion system (T6SS), which delivers effectors into neighboring cells that result in their death. Strains that are susceptible to the T6SS fail to establish symbiosis with a T6SS-positive strain within the same location of the squid light organ, which is a phenomenon termed strain incompatibility. This study investigates the regulation of the T6SS in V. fischeri strain FQ-A001. Here, we report that the expression of Hcp, a necessary structural component of the T6SS, depends on the alternative sigma factor σ54 and the bacterial enhancer binding protein VasH. VasH is necessary for FQ-A001 to kill other strains, suggesting that VasH-dependent regulation is essential for the T6SS of V. fischeri to affect intercellular interactions. In addition, this study demonstrates VasH-dependent transcription of hcp within host-associated populations of FQ-A001, suggesting that the T6SS is expressed within the host environment. Together, these findings establish a model for transcriptional control of hcp in V. fischeri within the squid light organ, thereby increasing understanding of how the T6SS is regulated during symbiosis.IMPORTANCE Animals harbor bacterial symbionts with specific traits that promote host fitness. Mechanisms that facilitate intercellular interactions among bacterial symbionts impact which bacterial lineages ultimately establish symbiosis with the host. How these mechanisms are regulated is poorly characterized in nonhuman bacterial symbionts. This study establishes a model for the transcriptional regulation of a contact-dependent killing machine, thereby increasing understanding of mechanisms by which different strains compete while establishing symbiosis.
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Abstract
Symbiotic bacteria use diverse strategies to compete for host colonization sites. However, little is known about the environmental cues that modulate interbacterial competition as they transition between free-living and host-associated lifestyles. We used the mutualistic relationship between Eupyrmna scolopes squid and Vibrio fischeri bacteria to investigate how intraspecific competition is regulated as symbionts move from the seawater to a host-like environment. We recently reported that V. fischeri uses a type VI secretion system (T6SS) for intraspecific competition during host colonization. Here, we investigated how environmental viscosity impacts T6SS-mediated competition by using a liquid hydrogel medium that mimics the viscous host environment. Our data demonstrate that although the T6SS is functionally inactive when cells are grown under low-viscosity liquid conditions similar to those found in seawater, exposure to a host-like high-viscosity hydrogel enhances T6SS expression and sheath formation, activates T6SS-mediated killing in as little as 30 min, and promotes the coaggregation of competing genotypes. Finally, the use of mass spectrometry-based proteomics revealed insights into how cells may prepare for T6SS competition during this habitat transition. These findings, which establish the use of a new hydrogel culture condition for studying T6SS interactions, indicate that V. fischeri rapidly responds to the physical environment to activate the competitive mechanisms used during host colonization.IMPORTANCE Bacteria often engage in interference competition to gain access to an ecological niche, such as a host. However, little is known about how the physical environment experienced by free-living or host-associated bacteria influences such competition. We used the bioluminescent squid symbiont Vibrio fischeri to study how environmental viscosity impacts bacterial competition. Our results suggest that upon transition from a planktonic environment to a host-like environment, V. fischeri cells activate their type VI secretion system, a contact-dependent interbacterial nanoweapon, to eliminate natural competitors. This work shows that competitor cells form aggregates under host-like conditions, thereby facilitating the contact required for killing, and reveals how V. fischeri regulates a key competitive mechanism in response to the physical environment.
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26
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Peñil-Celis A, Garcillán-Barcia MP. Crosstalk Between Type VI Secretion System and Mobile Genetic Elements. Front Mol Biosci 2019; 6:126. [PMID: 31799257 PMCID: PMC6863884 DOI: 10.3389/fmolb.2019.00126] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2019] [Accepted: 10/28/2019] [Indexed: 12/11/2022] Open
Abstract
Many bacterial processes require cell-cell contacts. Such are the cases of bacterial conjugation, one of the main horizontal gene transfer mechanisms that physically spreads DNA, and the type VI secretion systems (T6SSs), which deploy antibacterial activity. Bacteria depend on conjugation to adapt to changing environments, while T6SS killing activity could pose a threat to mating partners. Here we review the experimental evidences of overlapping and interaction between the T6SSs, bacterial conjugation, and conjugative genetic elements.
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Affiliation(s)
- Arancha Peñil-Celis
- Instituto de Biomedicina y Biotecnología de Cantabria, Universidad de Cantabria-Consejo Superior de Investigaciones Científicas, Santander, Spain
| | - M Pilar Garcillán-Barcia
- Instituto de Biomedicina y Biotecnología de Cantabria, Universidad de Cantabria-Consejo Superior de Investigaciones Científicas, Santander, Spain
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Espinoza-Vergara G, Noorian P, Silva-Valenzuela CA, Raymond BBA, Allen C, Hoque MM, Sun S, Johnson MS, Pernice M, Kjelleberg S, Djordjevic SP, Labbate M, Camilli A, McDougald D. Vibrio cholerae residing in food vacuoles expelled by protozoa are more infectious in vivo. Nat Microbiol 2019; 4:2466-74. [PMID: 31570868 DOI: 10.1038/s41564-019-0563-x] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2018] [Accepted: 07/19/2019] [Indexed: 11/09/2022]
Abstract
Vibrio cholerae interacts with many organisms in the environment, including heterotrophic protists (protozoa). Several species of protozoa have been reported to release undigested bacteria in expelled food vacuoles (EFVs) when feeding on some pathogens. While the production of EFVs has been reported, their biological role as a vector for the transmission of pathogens remains unknown. Here we report that ciliated protozoa release EFVs containing V. cholerae. The EFVs are stable, the cells inside them are protected from multiple stresses, and large numbers of cells escape when incubated at 37 °C or in the presence of nutrients. We show that OmpU, a major outer membrane protein positively regulated by ToxR, has a role in the production of EFVs. Notably, cells released from EFVs have growth and colonization advantages over planktonic cells both in vitro and in vivo. Our results suggest that EFVs facilitate V. cholerae survival in the environment, enhancing their infectious potential and may contribute to the dissemination of epidemic V. cholerae strains. These results improve our understanding of the mechanisms of persistence and the modes of transmission of V. cholerae and may further apply to other opportunistic pathogens that have been shown to be released by protists in EFVs.
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Wang S, Yang D, Wu X, Yi Z, Wang Y, Xin S, Wang D, Tian M, Li T, Qi J, Ding C, Yu S. The Ferric Uptake Regulator Represses Type VI Secretion System Function by Binding Directly to the clpV Promoter in Salmonella enterica Serovar Typhimurium. Infect Immun 2019; 87:e00562-19. [PMID: 31383745 DOI: 10.1128/IAI.00562-19] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2019] [Accepted: 07/25/2019] [Indexed: 12/16/2022] Open
Abstract
Type VI secretion systems (T6SSs) are highly conserved and complex protein secretion systems that deliver effector proteins into eukaryotic hosts or other bacteria. T6SSs are regulated precisely by a variety of regulatory systems, which enables bacteria to adapt to varied environments. A T6SS within Salmonella pathogenicity island 6 (SPI-6) is activated during infection, and it contributes to the pathogenesis, as well as interbacterial competition, of Salmonella enterica serovar Typhimurium (S. Typhimurium). However, the regulation of the SPI-6 T6SS in S. Typhimurium is not well understood. In this study, we found that the SPI-6 T6SS core gene clpV was significantly upregulated in response to the iron-depleted condition and during infection. The global ferric uptake regulator (Fur) was shown to repress the clpV expression in the iron-replete medium. Moreover, electrophoretic mobility shift and DNase I footprinting assays revealed that Fur binds directly to the clpV promoter region at multiple sites spanning the transcriptional start site. We also observed that the relieving of Fur-mediated repression on clpV contributed to the interbacterial competition activity and pathogenicity of S. Typhimurium. These findings provide insights into the direct regulation of Fur in the expression and functional activity of SPI-6 T6SS in S. Typhimurium and thus help to elucidate the mechanisms of bacterial adaptability and virulence.
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29
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Guckes KR, Cecere AG, Wasilko NP, Williams AL, Bultman KM, Mandel MJ, Miyashiro T. Incompatibility of Vibrio fischeri Strains during Symbiosis Establishment Depends on Two Functionally Redundant hcp Genes. J Bacteriol 2019; 201:e00221-19. [PMID: 31331977 DOI: 10.1128/JB.00221-19] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2019] [Accepted: 06/30/2019] [Indexed: 01/23/2023] Open
Abstract
Bacteria that have the capacity to fill the same niche will compete with one another for the space and resources available within an ecosystem. Such competition is heightened among different strains of the same bacterial species. Nevertheless, different strains often inhabit the same host. The molecular mechanisms that impact competition between different strains within the same host are poorly understood. To address this knowledge gap, the type VI secretion system (T6SS), which is a mechanism for bacteria to kill neighboring cells, was examined in the marine bacterium Vibrio fischeri Different strains of V. fischeri naturally colonize the light organ of the bobtail squid Euprymna scolopes The genome of FQ-A001, a T6SS-positive strain, features two hcp genes that are predicted to encode identical subunits of the T6SS. Coincubation assays showed that either hcp gene is sufficient for FQ-A001 to kill another strain via the T6SS in vitro Additionally, induction of hcp expression is sufficient to induce killing activity in an FQ-A001 mutant lacking both hcp genes. Squid colonization assays involving inocula of FQ-A001-derived strains mixed with ES114 revealed that both hcp genes must be deleted for FQ-A001 and ES114 to occupy the same space within the light organ. These experimental results provide insight into the genetic factors necessary for the T6SS of V. fischeri to function in vivo, thereby increasing understanding of the molecular mechanisms that impact strain diversity within a host.IMPORTANCE Different bacterial strains compete to occupy the same niche. The outcome of such competition can be affected by the type VI secretion system (T6SS), an intercellular killing mechanism of bacteria. Here an animal-bacterial symbiosis is used as a platform for study of the genetic factors that promote the T6SS-mediated killing of one strain by another. Identification of the molecular determinants of T6SS function in vivo contributes to the understanding of how different strains interact within a host.
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30
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McCarthy RR, Yu M, Eilers K, Wang Y, Lai E, Filloux A. Cyclic di-GMP inactivates T6SS and T4SS activity in Agrobacterium tumefaciens. Mol Microbiol 2019; 112:632-648. [PMID: 31102484 PMCID: PMC6771610 DOI: 10.1111/mmi.14279] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/15/2019] [Indexed: 01/17/2023]
Abstract
The Type VI secretion system (T6SS) is a bacterial nanomachine that delivers effector proteins into prokaryotic and eukaryotic preys. This secretion system has emerged as a key player in regulating the microbial diversity in a population. In the plant pathogen Agrobacterium tumefaciens, the signalling cascades regulating the activity of this secretion system are poorly understood. Here, we outline how the universal eubacterial second messenger cyclic di-GMP impacts the production of T6SS toxins and T6SS structural components. We demonstrate that this has a significant impact on the ability of the phytopathogen to compete with other bacterial species in vitro and in planta. Our results suggest that, as opposed to other bacteria, c-di-GMP turns down the T6SS in A. tumefaciens thus impacting its ability to compete with other bacterial species within the rhizosphere. We also demonstrate that elevated levels of c-di-GMP within the cell decrease the activity of the Type IV secretion system (T4SS) and subsequently the capacity of A. tumefaciens to transform plant cells. We propose that such peculiar control reflects on c-di-GMP being a key second messenger that silences energy-costing systems during early colonization phase and biofilm formation, while low c-di-GMP levels unleash T6SS and T4SS to advance plant colonization.
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Affiliation(s)
- Ronan R. McCarthy
- MRC Centre for Molecular Bacteriology and Infection, Department of Life SciencesImperial College LondonLondonSW7 2AZUK
- Division of Biosciences, Department of Life SciencesCollege of Health and Life Sciences, Brunel University LondonUxbridgeUB8 3PHUK
| | - Manda Yu
- Institute of Plant and Microbial BiologyAcademia SinicaTaipei11529Taiwan
| | - Kira Eilers
- MRC Centre for Molecular Bacteriology and Infection, Department of Life SciencesImperial College LondonLondonSW7 2AZUK
| | - Yi‐Chieh Wang
- Institute of Plant and Microbial BiologyAcademia SinicaTaipei11529Taiwan
| | - Erh‐Min Lai
- Institute of Plant and Microbial BiologyAcademia SinicaTaipei11529Taiwan
| | - Alain Filloux
- MRC Centre for Molecular Bacteriology and Infection, Department of Life SciencesImperial College LondonLondonSW7 2AZUK
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31
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Pena RT, Blasco L, Ambroa A, González-Pedrajo B, Fernández-García L, López M, Bleriot I, Bou G, García-Contreras R, Wood TK, Tomás M. Relationship Between Quorum Sensing and Secretion Systems. Front Microbiol 2019; 10:1100. [PMID: 31231316 PMCID: PMC6567927 DOI: 10.3389/fmicb.2019.01100] [Citation(s) in RCA: 137] [Impact Index Per Article: 27.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2019] [Accepted: 04/30/2019] [Indexed: 01/15/2023] Open
Abstract
Quorum sensing (QS) is a communication mechanism between bacteria that allows specific processes to be controlled, such as biofilm formation, virulence factor expression, production of secondary metabolites and stress adaptation mechanisms such as bacterial competition systems including secretion systems (SS). These SS have an important role in bacterial communication. SS are ubiquitous; they are present in both Gram-negative and Gram-positive bacteria and in Mycobacterium sp. To date, 8 types of SS have been described (T1SS, T2SS, T3SS, T4SS, T5SS, T6SS, T7SS, and T9SS). They have global functions such as the transport of proteases, lipases, adhesins, heme-binding proteins, and amidases, and specific functions such as the synthesis of proteins in host cells, adaptation to the environment, the secretion of effectors to establish an infectious niche, transfer, absorption and release of DNA, translocation of effector proteins or DNA and autotransporter secretion. All of these functions can contribute to virulence and pathogenesis. In this review, we describe the known types of SS and discuss the ones that have been shown to be regulated by QS. Due to the large amount of information about this topic in some pathogens, we focus mainly on Pseudomonas aeruginosa and Vibrio spp.
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Affiliation(s)
- Rocio Trastoy Pena
- Deapartamento de Microbiología y Parasitología, Complejo Hospitalario Universitario A Coruña (CHUAC), Instituto de Investigación Biomédica (INIBIC), Universidad de A Coruña (UDC), A Coruña, Spain
| | - Lucia Blasco
- Deapartamento de Microbiología y Parasitología, Complejo Hospitalario Universitario A Coruña (CHUAC), Instituto de Investigación Biomédica (INIBIC), Universidad de A Coruña (UDC), A Coruña, Spain
| | - Antón Ambroa
- Deapartamento de Microbiología y Parasitología, Complejo Hospitalario Universitario A Coruña (CHUAC), Instituto de Investigación Biomédica (INIBIC), Universidad de A Coruña (UDC), A Coruña, Spain
| | - Bertha González-Pedrajo
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, Mexico
| | - Laura Fernández-García
- Deapartamento de Microbiología y Parasitología, Complejo Hospitalario Universitario A Coruña (CHUAC), Instituto de Investigación Biomédica (INIBIC), Universidad de A Coruña (UDC), A Coruña, Spain
| | - Maria López
- Deapartamento de Microbiología y Parasitología, Complejo Hospitalario Universitario A Coruña (CHUAC), Instituto de Investigación Biomédica (INIBIC), Universidad de A Coruña (UDC), A Coruña, Spain
| | - Ines Bleriot
- Deapartamento de Microbiología y Parasitología, Complejo Hospitalario Universitario A Coruña (CHUAC), Instituto de Investigación Biomédica (INIBIC), Universidad de A Coruña (UDC), A Coruña, Spain
| | - German Bou
- Deapartamento de Microbiología y Parasitología, Complejo Hospitalario Universitario A Coruña (CHUAC), Instituto de Investigación Biomédica (INIBIC), Universidad de A Coruña (UDC), A Coruña, Spain
| | - Rodolfo García-Contreras
- Departamento de Microbiología y Parasitología, Facultad de Medicina, Universidad Nacional Autónoma de México, Mexico City, Mexico
| | - Thomas Keith Wood
- Department of Chemical Engineering, Pennsylvania State University, University Park, PA, United States
| | - Maria Tomás
- Deapartamento de Microbiología y Parasitología, Complejo Hospitalario Universitario A Coruña (CHUAC), Instituto de Investigación Biomédica (INIBIC), Universidad de A Coruña (UDC), A Coruña, Spain
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Metzger LC, Matthey N, Stoudmann C, Collas EJ, Blokesch M. Ecological implications of gene regulation by TfoX and TfoY among diverse Vibrio species. Environ Microbiol 2019; 21:2231-2247. [PMID: 30761714 PMCID: PMC6618264 DOI: 10.1111/1462-2920.14562] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2018] [Revised: 01/16/2019] [Accepted: 02/10/2019] [Indexed: 01/26/2023]
Abstract
Bacteria of the genus Vibrio are common members of aquatic environments where they compete with other prokaryotes and defend themselves against grazing predators. A macromolecular protein complex called the type VI secretion system (T6SS) is used for both purposes. Previous research showed that the sole T6SS of the human pathogen V. cholerae is induced by extracellular (chitin) or intracellular (low c‐di‐GMP levels) cues and that these cues lead to distinctive signalling pathways for which the proteins TfoX and TfoY serve as master regulators. In this study, we tested whether the TfoX‐ and TfoY‐mediated regulation of T6SS, concomitantly with natural competence or motility, was conserved in non‐cholera Vibrio species, and if so, how these regulators affected the production of individual T6SSs in double‐armed vibrios. We show that, alongside representative competence genes, TfoX regulates at least one T6SS in all tested Vibrio species. TfoY, on the other hand, fostered motility in all vibrios but had a more versatile T6SS response in that it did not foster T6SS‐mediated killing in all tested vibrios. Collectively, our data provide evidence that the TfoX‐ and TfoY‐mediated signalling pathways are mostly conserved in diverse Vibrio species and important for signal‐specific T6SS induction.
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Affiliation(s)
- Lisa C Metzger
- Laboratory of Molecular Microbiology, Global Health Institute, School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Noémie Matthey
- Laboratory of Molecular Microbiology, Global Health Institute, School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Candice Stoudmann
- Laboratory of Molecular Microbiology, Global Health Institute, School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Esther J Collas
- Laboratory of Molecular Microbiology, Global Health Institute, School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Melanie Blokesch
- Laboratory of Molecular Microbiology, Global Health Institute, School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
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Cruite J, Succo P, Raychaudhuri S, Kull FJ. Crystal structure of an inactive variant of the quorum-sensing master regulator HapR from the protease-deficient non-O1, non-O139 Vibrio cholerae strain V2. Acta Crystallogr F Struct Biol Commun 2018; 74:331-336. [PMID: 29870016 PMCID: PMC5987740 DOI: 10.1107/s2053230x18006519] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2018] [Accepted: 04/27/2018] [Indexed: 11/10/2022] Open
Abstract
HapR is a TetR-family transcriptional regulator that controls quorum sensing in Vibrio cholerae, the causative agent of cholera. HapR regulates the expression of hemagglutinin protease, virulence and biofilm genes. The crystal structure of wild-type HapR from V. cholerae strain O1 El Tor C6706 has previously been solved. In this study, the structure of a DNA-binding-deficient variant of HapR (HapRV2) derived from the protease-deficient V. cholerae serotype O37 strain V2 is reported. The structure reveals no structural differences compared with wild-type HapR. However, structural alignment of HapRV2 with the TetR-family member QacR in complex with its operator DNA suggests that the aspartate residue located between the regulatory and DNA-binding domains may clash with and electrostatically repel the phosphate backbone of DNA to prevent binding.
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Affiliation(s)
- Justin Cruite
- Department of Biochemistry, Geisel School of Medicine, Dartmouth College, Hanover, New Hampshire, USA
| | - Patrick Succo
- College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, Colorado, USA
| | - Saumya Raychaudhuri
- Institute of Microbial Technology, Chandigarh, Council of Scientific and Industrial Research, Chandigarh 160 036, India
| | - F. Jon Kull
- Department of Biochemistry, Geisel School of Medicine, Dartmouth College, Hanover, New Hampshire, USA
- Department of Chemistry, Dartmouth College, Hanover, New Hampshire, USA
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Zhang Y, Gao H, Osei-Adjei G, Zhang Y, Yang W, Yang H, Yin Z, Huang X, Zhou D. Transcriptional Regulation of the Type VI Secretion System 1 Genes by Quorum Sensing and ToxR in Vibrio parahaemolyticus. Front Microbiol 2017; 8:2005. [PMID: 29085350 PMCID: PMC5650642 DOI: 10.3389/fmicb.2017.02005] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2017] [Accepted: 09/29/2017] [Indexed: 12/26/2022] Open
Abstract
Vibrio parahaemolyticus, the leading cause of seafood-associated gastroenteritis, harbors two separate T6SSs on chromosomes 1 and 2, i.e., T6SS1 (VP1386-1420) and T6SS2 (VPA1025-1046). T6SS1 contains at least 7 putative operons: VP1386-1387, VP1388-1390, VP1392-1391, VP1393-1406, VP1400-1406, VP1409-1407, and VP1410-1420. V. parahaemolyticus AphA and OpaR are the two master regulators of quorum sensing (QS) system that are highly expressed at low cell density and high cell density, respectively. ToxR is a membrane-bound virulence regulatory protein conserved across the Vibrio family. In the present work, we show that ToxR coordinates with AphA and OpaR to repress T6SS1 expression in V. parahaemolyticus. OpaR binds to the promoters of VP1388-1390, VP1400-1406, and VP1409-1407 to repress their transcription, but it appears to negatively regulate VP1393-1406 transcription in an indirect manner. By contrast, AphA negatively regulated the above four T6SS1 operons in an indirect manner. In addition, ToxR binds to the promoters of VP1400-1406 and VP1409-1407 to inhibit their transcription, but it presents an indirect interaction with VP1388-1390 and VP1393-1406 promoters. Notably, the expression of ToxR also manifested in a QS-dependent manner and the highest expression occurred at LCD. Meanwhile, the highest expression of T6SS1 occurred at an OD600 value of 0.6 to 0.8 due to the tight regulation of ToxR and QS, suggesting T6SS1 functions only during the mid-logarithmic growth phase. These observations provide significant insight into the molecular mechanism of T6SS1 gene regulation by QS and ToxR in V. parahaemolyticus.
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Affiliation(s)
- Yiquan Zhang
- School of Medicine, Jiangsu University, Zhenjiang, China
| | - He Gao
- State Key Laboratory for Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Centre for Disease Control and Prevention, Beijing, China
| | | | - Ying Zhang
- School of Medicine, Jiangsu University, Zhenjiang, China
| | - Wenhui Yang
- Department of Biosafety, State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, China
| | - Huiying Yang
- Department of Biosafety, State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, China
| | - Zhe Yin
- Department of Biosafety, State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, China
| | - Xinxiang Huang
- School of Medicine, Jiangsu University, Zhenjiang, China
| | - Dongsheng Zhou
- Department of Biosafety, State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, China
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Wang Y, Li Y, Wang J, Wang X. FleQ regulates both the type VI secretion system and flagella inPseudomonas putida. Biotechnol Appl Biochem 2017; 65:419-427. [DOI: 10.1002/bab.1611] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2017] [Revised: 08/29/2017] [Accepted: 09/12/2017] [Indexed: 12/24/2022]
Affiliation(s)
- Yuzhou Wang
- School of BiotechnologyJiangnan University Wuxi People's Republic of China
| | - Ye Li
- State Key Laboratory of Food Science and TechnologyJiangnan University Wuxi People's Republic of China
| | - Jianli Wang
- School of BiotechnologyJiangnan University Wuxi People's Republic of China
| | - Xiaoyuan Wang
- State Key Laboratory of Food Science and TechnologyJiangnan University Wuxi People's Republic of China
- School of BiotechnologyJiangnan University Wuxi People's Republic of China
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Abstract
Bacterial type VI secretion systems (T6SSs) function as contractile nanomachines to puncture target cells and deliver lethal effectors. In the 10 years since the discovery of the T6SS, much has been learned about the structure and function of this versatile protein secretion apparatus. Most of the conserved protein components that comprise the T6SS apparatus itself have been identified and ascribed specific functions. In addition, numerous effector proteins that are translocated by the T6SS have been identified and characterized. These protein effectors usually represent toxic cargoes that are delivered by the attacker cell to a target cell. Researchers in the field are beginning to better understand the lifestyle or physiology that dictates when bacteria normally express their T6SS. In this article, we consider what is known about the structure and regulation of the T6SS, the numerous classes of antibacterial effector T6SS substrates, and how the action of the T6SS relates to a given lifestyle or behavior in certain bacteria.
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Conner JG, Teschler JK, Jones CJ, Yildiz FH. Staying Alive: Vibrio cholerae's Cycle of Environmental Survival, Transmission, and Dissemination. Microbiol Spectr 2016; 4. [PMID: 27227302 DOI: 10.1128/microbiolspec.VMBF-0015-2015] [Citation(s) in RCA: 74] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Infectious diseases kill nearly 9 million people annually. Bacterial pathogens are responsible for a large proportion of these diseases, and the bacterial agents of pneumonia, diarrhea, and tuberculosis are leading causes of death and disability worldwide. Increasingly, the crucial role of nonhost environments in the life cycle of bacterial pathogens is being recognized. Heightened scrutiny has been given to the biological processes impacting pathogen dissemination and survival in the natural environment, because these processes are essential for the transmission of pathogenic bacteria to new hosts. This chapter focuses on the model environmental pathogen Vibrio cholerae to describe recent advances in our understanding of how pathogens survive between hosts and to highlight the processes necessary to support the cycle of environmental survival, transmission, and dissemination. We describe the physiological and molecular responses of V. cholerae to changing environmental conditions, focusing on its survival in aquatic reservoirs between hosts and its entry into and exit from human hosts.
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Zhao M, Zhang L, Lv S, Zhang C, Wang L, Chen H, Zhou Y, Lou J. IQGAP1 Mediates Hcp1-Promoted Escherichia coli Meningitis by Stimulating the MAPK Pathway. Front Cell Infect Microbiol 2017; 7:132. [PMID: 28469997 PMCID: PMC5395654 DOI: 10.3389/fcimb.2017.00132] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2016] [Accepted: 03/31/2017] [Indexed: 01/14/2023] Open
Abstract
Escherichia coli-induced meningitis remains a life-threatening disease despite recent advances in the field of antibiotics-based therapeutics, necessitating continued research on its pathogenesis. The current study aims to elucidate the mechanism through which hemolysin-coregulated protein 1 (Hcp1) induces the apoptosis of human brain microvascular endothelial cells (HBMEC). Co-immunoprecipitation coupled with mass spectrometric (MS) characterization led to the identification of IQ motif containing GTPase activating protein 1 (IQGAP1) as a downstream target of Hcp1. IQGAP1 was found to be up-regulated by Hcp1 treatment and mediate the stimulation of HBMEC apoptosis. It was shown that Hcp1 could compete against Smurf1 for binding to IQGAP1, thereby rescuing the latter from ubiquitin-dependent degradation. Subsequent study suggested that IQGAP1 could stimulate the MAPK signaling pathway by promoting the phosphorylation of ERK1/2, an effect that was blocked by U0126, an MAPK inhibitor. Furthermore, U0126 also demonstrated therapeutic potential against E. coli meningitis in a mouse model. Taken together, our results suggested the feasibility of targeting the MAPK pathway as a putative therapeutic strategy against bacterial meningitis.
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Affiliation(s)
- Mingna Zhao
- Department of Laboratory Medicine, Shanghai Chest Hospital, Shanghai Jiao Tong UniversityShanghai, China
| | - Lingfei Zhang
- Center for RNA Research, State Key Laboratory of Molecular Biology-University of Chinese Academy of Sciences, Institute of Biochemistry and Cell Biology Shanghai Institutes for Biological Sciences Chinese Academy of SciencesShanghai, China.,Department of Anatomy, Histology and Embryology, Shanghai Medical College, Fudan UniversityShanghai, China
| | - Shaogang Lv
- Department of Laboratory Medicine, Shanghai Chest Hospital, Shanghai Jiao Tong UniversityShanghai, China
| | - Chenzi Zhang
- Department of Laboratory Medicine, Shanghai Chest Hospital, Shanghai Jiao Tong UniversityShanghai, China
| | - Lin Wang
- Department of Laboratory Medicine, Shanghai Chest Hospital, Shanghai Jiao Tong UniversityShanghai, China
| | - Hong Chen
- Department of Anatomy, Histology and Embryology, Shanghai Medical College, Fudan UniversityShanghai, China
| | - Yan Zhou
- Department of Microbiology and Immunobiology, Harvard Medical SchoolBoston, MA, USA
| | - Jiatao Lou
- Department of Laboratory Medicine, Shanghai Chest Hospital, Shanghai Jiao Tong UniversityShanghai, China
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Joshi A, Kostiuk B, Rogers A, Teschler J, Pukatzki S, Yildiz FH. Rules of Engagement: The Type VI Secretion System in Vibrio cholerae. Trends Microbiol 2017; 25:267-279. [PMID: 28027803 PMCID: PMC5365375 DOI: 10.1016/j.tim.2016.12.003] [Citation(s) in RCA: 81] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2016] [Revised: 12/04/2016] [Accepted: 12/07/2016] [Indexed: 11/16/2022]
Abstract
Microbial species often exist in complex communities where they must avoid predation and compete for favorable niches. The type VI secretion system (T6SS) is a contact-dependent bacterial weapon that allows for direct killing of competitors through the translocation of proteinaceous toxins. Vibrio cholerae is a Gram-negative pathogen that can use its T6SS during antagonistic interactions with neighboring prokaryotic and eukaryotic competitors. The T6SS not only promotes V. cholerae's survival during its aquatic and host life cycles, but also influences its evolution by facilitating horizontal gene transfer. This review details the recent insights regarding the structure and function of the T6SS as well as the diverse signals and regulatory pathways that control its activation in V. cholerae.
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Affiliation(s)
- Avatar Joshi
- Department of Microbiology and Environmental Toxicology, University of Santa Cruz, Santa Cruz, California, USA
| | - Benjamin Kostiuk
- Department of Medical Microbiology and Immunology, University of Alberta, Alberta, Canada
| | - Andrew Rogers
- Department of Microbiology and Environmental Toxicology, University of Santa Cruz, Santa Cruz, California, USA
| | - Jennifer Teschler
- Department of Microbiology and Environmental Toxicology, University of Santa Cruz, Santa Cruz, California, USA
| | - Stefan Pukatzki
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, Colorado, USA
| | - Fitnat H Yildiz
- Department of Microbiology and Environmental Toxicology, University of Santa Cruz, Santa Cruz, California, USA.
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Huang Y, Du P, Zhao M, Liu W, Du Y, Diao B, Li J, Kan B, Liang W. Functional Characterization and Conditional Regulation of the Type VI Secretion System in Vibrio fluvialis. Front Microbiol 2017; 8:528. [PMID: 28424671 PMCID: PMC5371669 DOI: 10.3389/fmicb.2017.00528] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2016] [Accepted: 03/14/2017] [Indexed: 01/22/2023] Open
Abstract
Vibrio fluvialis is an emerging foodborne pathogen of increasing public health concern. The mechanism(s) that contribute to the bacterial survival and disease are still poorly understood. In other bacterial species, type VI secretion systems (T6SSs) are known to contribute to bacterial pathogenicity by exerting toxic effects on host cells or competing bacterial species. In this study, we characterized the genetic organization and prevalence of two T6SS gene clusters (VflT6SS1 and VflT6SS2) in V. fluvialis. VflT6SS2 harbors three “orphan” hcp-vgrG modules and was more prevalent than VflT6SS1 in our isolates. We showed that VflT6SS2 is functionally active under low (25°C) and warm (30°C) temperatures by detecting the secretion of a T6SS substrate, Hcp. This finding suggests that VflT6SS2 may play an important role in the survival of the bacterium in the aquatic environment. The secretion of Hcp is growth phase-dependent and occurs in a narrow range of the growth phase (OD600 from 1.0 to 2.0). Osmolarity also regulates the function of VflT6SS2, as evidenced by our finding that increasing salinity (from 170 to 855 mM of NaCl) and exposure to high osmolarity KCl, sucrose, trehalose, or mannitol (equivalent to 340 mM of NaCl) induced significant secretion of Hcp under growth at 30°C. Furthermore, we found that although VflT6SS2 was inactive at a higher temperature (37°C), it became activated at this temperature if higher salinity conditions were present (from 513 to 855 mM of NaCl), indicating that it may be able to function under certain conditions in the infected host. Finally, we showed that the functional expression of VflT6SS2 is associated with anti-bacterial activity. This activity is Hcp-dependent and requires vasH, a transcriptional regulator of T6SS. In sum, our study demonstrates that VflT6SS2 provides V. fluvialis with an enhanced competitive fitness in the marine environment, and its activity is regulated by environmental signals, such as temperature and osmolarity.
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Affiliation(s)
- Yuanming Huang
- State Key Laboratory of Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and PreventionBeijing, China.,Collaborative Innovation Centre for Diagnosis and Treatment of Infectious DiseasesHangzhou, China
| | - Pengcheng Du
- Beijing Key Laboratory of Emerging Infectious Diseases, Institute of Infectious Diseases, Beijing Ditan Hospital, Capital Medical UniversityBeijing, China
| | - Meng Zhao
- State Key Laboratory of Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and PreventionBeijing, China
| | - Wei Liu
- State Key Laboratory of Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and PreventionBeijing, China
| | - Yu Du
- State Key Laboratory of Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and PreventionBeijing, China
| | - Baowei Diao
- State Key Laboratory of Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and PreventionBeijing, China
| | - Jie Li
- State Key Laboratory of Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and PreventionBeijing, China
| | - Biao Kan
- State Key Laboratory of Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and PreventionBeijing, China.,Collaborative Innovation Centre for Diagnosis and Treatment of Infectious DiseasesHangzhou, China
| | - Weili Liang
- State Key Laboratory of Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and PreventionBeijing, China.,Collaborative Innovation Centre for Diagnosis and Treatment of Infectious DiseasesHangzhou, China
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Boyd EF, Carpenter MR, Chowdhury N, Cohen AL, Haines-Menges BL, Kalburge SS, Kingston JJ, Lubin JB, Ongagna-Yhombi SY, Whitaker WB. Post-Genomic Analysis of Members of the Family Vibrionaceae. Microbiol Spectr 2015; 3. [PMID: 26542048 DOI: 10.1128/microbiolspec.VE-0009-2014] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Similar to other genera and species of bacteria, whole genomic sequencing has revolutionized how we think about and address questions of basic Vibrio biology. In this review we examined 36 completely sequenced and annotated members of the Vibrionaceae family, encompassing 12 different species of the genera Vibrio, Aliivibrio, and Photobacterium. We reconstructed the phylogenetic relationships among representatives of this group of bacteria by using three housekeeping genes and 16S rRNA sequences. With an evolutionary framework in place, we describe the occurrence and distribution of primary and alternative sigma factors, global regulators present in all bacteria. Among Vibrio we show that the number and function of many of these sigma factors differs from species to species. We also describe the role of the Vibrio-specific regulator ToxRS in fitness and survival. Examination of the biochemical capabilities was and still is the foundation of classifying and identifying new Vibrio species. Using comparative genomics, we examine the distribution of carbon utilization patterns among Vibrio species as a possible marker for understanding bacteria-host interactions. Finally, we discuss the significant role that horizontal gene transfer, specifically, the distribution and structure of integrons, has played in Vibrio evolution.
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Xue J, Tan B, Yang S, Luo M, Xia H, Zhang X, Zhou X, Yang X, Yang R, Li Y, Qiu J. Influence of cAMP receptor protein (CRP) on bacterial virulence and transcriptional regulation of allS by CRP in Klebsiella pneumoniae. Gene 2016; 593:28-33. [PMID: 27502416 DOI: 10.1016/j.gene.2016.08.006] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Revised: 08/01/2016] [Accepted: 08/04/2016] [Indexed: 01/23/2023]
Abstract
cAMP receptor protein (CRP) is one of the most important transcriptional regulators, which can regulate large quantities of operons in different bacteria. The gene allS was well-known as allantoin-utilizing capability and involving in bacterial virulence in Klebsiella pneumoniae (K. pneumoniae). The specific DNA recognition motif of transcription regulator CRP was found in allS promoter region. Therefore, this study is aimed to investigate the function of CRP on virulence and its transcriptional regulation mechanism to gene allS in K. pneumoniae. The wild-type (WT) K. pneumoniae NTUH-2044, crp knockout (Kp-Δcrp) and the complemented knockout (KpC-Δcrp) strains were used to determine the function of crp gene. The lacZ fusion, qRT-PCR, electrophoretic mobility shift and DNase I footprinting assays were performed to study the transcriptional regulation of CRP on allS. The result showed a decreased virulence in crp knockout strain. Complement through supplementing crp fragment in expression plasmid partially restore virulence of knockout bacteria. The CRP could bind to the allS promoter-proximal region and the binding site was further refined to be located from 60bp to 94bp upstream of the allS promoter. Based on these results, we proposed that CRP is an essential virulence regulator and knock out of crp gene will result in reduced virulence in K. pneumoniae. In the meantime, the transcription of gene allS is positively regulated by CRP via directly binding to upstream of allS promoter.
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Affiliation(s)
- Jian Xue
- School of Public Health and Management, Chongqing Medical University, Research Center for Medicine and Social Development, Innovation Center for Social Risk Governance in Health, Chongqing 400016, China
| | - Bin Tan
- Yubei District Center for Disease Control and Prevention, Chongqing 401120, China
| | - Shiya Yang
- School of Public Health and Management, Chongqing Medical University, Research Center for Medicine and Social Development, Innovation Center for Social Risk Governance in Health, Chongqing 400016, China
| | - Mei Luo
- School of Public Health and Management, Chongqing Medical University, Research Center for Medicine and Social Development, Innovation Center for Social Risk Governance in Health, Chongqing 400016, China
| | - Huiming Xia
- School of Medicine, Johns Hopkins University, Baltimore, MD, USA
| | - Xian Zhang
- School of Public Health and Management, Chongqing Medical University, Research Center for Medicine and Social Development, Innovation Center for Social Risk Governance in Health, Chongqing 400016, China
| | - Xipeng Zhou
- School of Public Health and Management, Chongqing Medical University, Research Center for Medicine and Social Development, Innovation Center for Social Risk Governance in Health, Chongqing 400016, China
| | - Xianxian Yang
- School of Public Health and Management, Chongqing Medical University, Research Center for Medicine and Social Development, Innovation Center for Social Risk Governance in Health, Chongqing 400016, China
| | - Ruifu Yang
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, China
| | - Yingli Li
- School of Public Health and Management, Chongqing Medical University, Research Center for Medicine and Social Development, Innovation Center for Social Risk Governance in Health, Chongqing 400016, China.
| | - Jingfu Qiu
- School of Public Health and Management, Chongqing Medical University, Research Center for Medicine and Social Development, Innovation Center for Social Risk Governance in Health, Chongqing 400016, China.
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Townsley L, Sison Mangus MP, Mehic S, Yildiz FH. Response of Vibrio cholerae to Low-Temperature Shifts: CspV Regulation of Type VI Secretion, Biofilm Formation, and Association with Zooplankton. Appl Environ Microbiol 2016; 82:4441-52. [PMID: 27208110 DOI: 10.1128/AEM.00807-16] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2016] [Accepted: 05/02/2016] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED The ability to sense and adapt to temperature fluctuation is critical to the aquatic survival, transmission, and infectivity of Vibrio cholerae, the causative agent of the disease cholera. Little information is available on the physiological changes that occur when V. cholerae experiences temperature shifts. The genome-wide transcriptional profile of V. cholerae upon a shift in human body temperature (37°C) to lower temperatures, 15°C and 25°C, which mimic those found in the aquatic environment, was determined. Differentially expressed genes included those involved in the cold shock response, biofilm formation, type VI secretion, and virulence. Analysis of a mutant lacking the cold shock gene cspV, which was upregulated >50-fold upon a low-temperature shift, revealed that it regulates genes involved in biofilm formation and type VI secretion. CspV controls biofilm formation through modulation of the second messenger cyclic diguanylate and regulates type VI-mediated interspecies killing in a temperature-dependent manner. Furthermore, a strain lacking cspV had significant defects for attachment and type VI-mediated killing on the surface of the aquatic crustacean Daphnia magna Collectively, these studies reveal that cspV is a major regulator of the temperature downshift response and plays an important role in controlling cellular processes crucial to the infectious cycle of V. cholerae IMPORTANCE Little is known about how human pathogens respond and adapt to ever-changing parameters of natural habitats outside the human host and how environmental adaptation alters dissemination. Vibrio cholerae, the causative agent of the severe diarrheal disease cholera, experiences fluctuations in temperature in its natural aquatic habitats and during the infection process. Furthermore, temperature is a critical environmental signal governing the occurrence of V. cholerae and cholera outbreaks. In this study, we showed that V. cholerae reprograms its transcriptome in response to fluctuations in temperature, which results in changes to biofilm formation and type VI secretion system activation. These processes in turn impact environmental survival and the virulence potential of this pathogen.
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Tang L, Yue S, Li G, Li J, Wang X, Li S, Mo Z. Expression, secretion and bactericidal activity of type VI secretion system in Vibrio anguillarum. Arch Microbiol 2016; 198:751-60. [DOI: 10.1007/s00203-016-1236-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2016] [Revised: 04/21/2016] [Accepted: 05/05/2016] [Indexed: 10/21/2022]
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Aung KM, Sjöström AE, von Pawel-Rammingen U, Riesbeck K, Uhlin BE, Wai SN. Naturally Occurring IgG Antibodies Provide Innate Protection against Vibrio cholerae Bacteremia by Recognition of the Outer Membrane Protein U. J Innate Immun 2016; 8:269-83. [PMID: 26934383 DOI: 10.1159/000443646] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2015] [Accepted: 12/24/2015] [Indexed: 01/18/2023] Open
Abstract
Cholera epidemics are caused by Vibrio cholerae serogroups O1 and O139, whereas strains collectively known as non-O1/non-O139 V. cholerae are found in cases of extraintestinal infections and bacteremia. The mechanisms and factors influencing the occurrence of bacteremia and survival of V. cholerae in normal human serum have remained unclear. We found that naturally occurring IgG recognizing V. cholerae outer membrane protein U (OmpU) mediates a serum-killing effect in a complement C1q-dependent manner. Moreover, outer membrane vesicles (OMVs) containing OmpU caused enhanced survival of highly serum-sensitive classical V. cholerae in a dose-dependent manner. OMVs from wild-type and ompU mutant V. cholerae thereby provided a novel means to verify by extracellular transcomplementation the involvement of OmpU. Our data conclusively indicate that loss, or reduced expression, of OmpU imparts resistance to V. cholerae towards serum killing. We propose that the difference in OmpU protein levels is a plausible reason for differences in serum resistance and the ability to cause bacteremia observed among V. cholerae biotypes. Our findings provide a new perspective on how naturally occurring antibodies, perhaps induced by members of the microbiome, may play a role in the recognition of pathogens and the provocation of innate immune defense against bacteremia.
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Affiliation(s)
- Kyaw Min Aung
- The Laboratory for Molecular Infection Medicine Sweden (MIMS), Department of Molecular Biology, Umex00E5; University, Umex00E5;, Sweden
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Rogers A, Townsley L, Gallego-Hernandez AL, Beyhan S, Kwuan L, Yildiz FH. The LonA Protease Regulates Biofilm Formation, Motility, Virulence, and the Type VI Secretion System in Vibrio cholerae. J Bacteriol 2016; 198:973-85. [PMID: 26755629 DOI: 10.1128/JB.00741-15] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2015] [Accepted: 01/05/2016] [Indexed: 02/04/2023] Open
Abstract
UNLABELLED The presence of the Lon protease in all three domains of life hints at its biological importance. The prokaryotic Lon protease is responsible not only for degrading abnormal proteins but also for carrying out the proteolytic regulation of specific protein targets. Posttranslational regulation by Lon is known to affect a variety of physiological traits in many bacteria, including biofilm formation, motility, and virulence. Here, we identify the regulatory roles of LonA in the human pathogen Vibrio cholerae. We determined that the absence of LonA adversely affects biofilm formation, increases swimming motility, and influences intracellular levels of cyclic diguanylate. Whole-genome expression analysis revealed that the message abundance of genes involved in biofilm formation was decreased but that the message abundances of those involved in virulence and the type VI secretion system were increased in a lonA mutant compared to the wild type. We further demonstrated that a lonA mutant displays an increase in type VI secretion system activity and is markedly defective in colonization of the infant mouse. These findings suggest that LonA plays a critical role in the environmental survival and virulence of V. cholerae. IMPORTANCE Bacteria utilize intracellular proteases to degrade damaged proteins and adapt to changing environments. The Lon protease has been shown to be important for environmental adaptation and plays a crucial role in regulating the motility, biofilm formation, and virulence of numerous plant and animal pathogens. We find that LonA of the human pathogen V. cholerae is in line with this trend, as the deletion of LonA leads to hypermotility and defects in both biofilm formation and colonization of the infant mouse. In addition, we show that LonA regulates levels of cyclic diguanylate and the type VI secretion system. Our observations add to the known regulatory repertoire of the Lon protease and the current understanding of V. cholerae physiology.
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Abstract
Biotic and abiotic surfaces in marine waters are rapidly colonized by microorganisms. Surface colonization and subsequent biofilm formation and development provide numerous advantages to these organisms and support critical ecological and biogeochemical functions in the changing marine environment. Microbial surface association also contributes to deleterious effects such as biofouling, biocorrosion, and the persistence and transmission of harmful or pathogenic microorganisms and their genetic determinants. The processes and mechanisms of colonization as well as key players among the surface-associated microbiota have been studied for several decades. Accumulating evidence indicates that specific cell-surface, cell-cell, and interpopulation interactions shape the composition, structure, spatiotemporal dynamics, and functions of surface-associated microbial communities. Several key microbial processes and mechanisms, including (i) surface, population, and community sensing and signaling, (ii) intraspecies and interspecies communication and interaction, and (iii) the regulatory balance between cooperation and competition, have been identified as critical for the microbial surface association lifestyle. In this review, recent progress in the study of marine microbial surface colonization and biofilm development is synthesized and discussed. Major gaps in our knowledge remain. We pose questions for targeted investigation of surface-specific community-level microbial features, answers to which would advance our understanding of surface-associated microbial community ecology and the biogeochemical functions of these communities at levels from molecular mechanistic details through systems biological integration.
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He Y, Wang H, Chen L. Comparative secretomics reveals novel virulence-associated factors of Vibrio parahaemolyticus. Front Microbiol 2015; 6:707. [PMID: 26236293 PMCID: PMC4505105 DOI: 10.3389/fmicb.2015.00707] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2015] [Accepted: 06/26/2015] [Indexed: 01/03/2023] Open
Abstract
Vibrio parahaemolyticus is a causative agent of serious human seafood-borne gastroenteritis disease and even death. In this study, for the first time, we obtained the secretomic profiles of seven V. parahaemolyticus strains of clinical and food origins. The strains exhibited various toxic genotypes and phenotypes of antimicrobial susceptibility and heavy metal resistance, five of which were isolated from aquatic products in Shanghai, China. Fourteen common extracellular proteins were identified from the distinct secretomic profiles using the two-dimensional gel electrophoresis (2-DE) and liquid chromatography tandem mass spectrometry (LC-MS/MS) techniques. Of these, half were involved in protein synthesis and sugar transport of V. parahaemolyticus. Strikingly, six identified proteins were virulence-associated factors involved in the pathogenicity of some other pathogenic bacteria, including the translation elongation factor EF-Tu, pyridoxine 5′-phosphate synthase, σ54 modulation protein, dihydrolipoyl dehydrogenase, transaldolase and phosphoglycerate kinase. In addition, comparative secretomics also revealed several extracellular proteins that have not been described in any bacteria, such as the ribosome-recycling factor, translation elongation factor EF-Ts, phosphocarrier protein HPr and maltose-binding protein MalE. The results in this study will facilitate the better understanding of the pathogenesis of V. parahaemolyticus and provide data in support of novel vaccine candidates against the leading seafood-borne pathogen worldwide.
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Affiliation(s)
- Yu He
- Key Laboratory of Quality and Safety Risk Assessment for Aquatic Products on Storage and Preservation (Shanghai), China Ministry of Agriculture, College of Food Science and Technology, Shanghai Ocean University Shanghai, China
| | - Hua Wang
- Department of Food Science and Technology, The Ohio State University Columbus, OH, USA
| | - Lanming Chen
- Key Laboratory of Quality and Safety Risk Assessment for Aquatic Products on Storage and Preservation (Shanghai), China Ministry of Agriculture, College of Food Science and Technology, Shanghai Ocean University Shanghai, China
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Weber BS, Ly PM, Irwin JN, Pukatzki S, Feldman MF. A multidrug resistance plasmid contains the molecular switch for type VI secretion in Acinetobacter baumannii. Proc Natl Acad Sci U S A 2015; 112:9442-7. [PMID: 26170289 DOI: 10.1073/pnas.1502966112] [Citation(s) in RCA: 130] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Infections with Acinetobacter baumannii, one of the most troublesome and least studied multidrug-resistant superbugs, are increasing at alarming rates. A. baumannii encodes a type VI secretion system (T6SS), an antibacterial apparatus of Gram-negative bacteria used to kill competitors. Expression of the T6SS varies among different strains of A. baumannii, for which the regulatory mechanisms are unknown. Here, we show that several multidrug-resistant strains of A. baumannii harbor a large, self-transmissible resistance plasmid that carries the negative regulators for T6SS. T6SS activity is silenced in plasmid-containing, antibiotic-resistant cells, while part of the population undergoes frequent plasmid loss and activation of the T6SS. This activation results in T6SS-mediated killing of competing bacteria but renders A. baumannii susceptible to antibiotics. Our data show that a plasmid that has evolved to harbor antibiotic resistance genes plays a role in the differentiation of cells specialized in the elimination of competing bacteria.
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Cheng AT, Ottemann KM, Yildiz FH. Vibrio cholerae Response Regulator VxrB Controls Colonization and Regulates the Type VI Secretion System. PLoS Pathog 2015; 11:e1004933. [PMID: 26000450 DOI: 10.1371/journal.ppat.1004933] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2015] [Accepted: 05/04/2015] [Indexed: 11/19/2022] Open
Abstract
Two-component signal transduction systems (TCS) are used by bacteria to sense and respond to their environment. TCS are typically composed of a sensor histidine kinase (HK) and a response regulator (RR). The Vibrio cholerae genome encodes 52 RR, but the role of these RRs in V. cholerae pathogenesis is largely unknown. To identify RRs that control V. cholerae colonization, in-frame deletions of each RR were generated and the resulting mutants analyzed using an infant mouse intestine colonization assay. We found that 12 of the 52 RR were involved in intestinal colonization. Mutants lacking one previously uncharacterized RR, VCA0566 (renamed VxrB), displayed a significant colonization defect. Further experiments showed that VxrB phosphorylation state on the predicted conserved aspartate contributes to intestine colonization. The VxrB regulon was determined using whole genome expression analysis. It consists of several genes, including those genes that create the type VI secretion system (T6SS). We determined that VxrB is required for T6SS expression using several in vitro assays and bacterial killing assays, and furthermore that the T6SS is required for intestinal colonization. vxrB is encoded in a four gene operon and the other vxr operon members also modulate intestinal colonization. Lastly, though ΔvxrB exhibited a defect in single-strain intestinal colonization, the ΔvxrB strain did not show any in vitro growth defect. Overall, our work revealed that a small set of RRs is required for intestinal colonization and one of these regulators, VxrB affects colonization at least in part through its regulation of T6SS genes. Pathogenic bacteria experience varying conditions during infection of human hosts and often use two-component signal transduction systems (TCSs) to monitor their environment. TCS consists of a histidine kinase (HK), which senses environmental signals, and a corresponding response regulator (RR), which mediates a cellular response. The genome of the human pathogen V. cholerae contains a multitude of genes encoding HKs and RRs proteins. In the present study, we systematically analyzed the role of each V. cholerae RR for its role in pathogenesis. We identified a previously uncharacterized RR, VxrB, as a new virulence factor. We demonstrated that VxrB controls expression of the type VI secretion system (T6SS), a virulence nanomachine that directly translocates effectors into bacterial or host cells, thereby facilitating colonization by competing with sister cells and intestinal microbiota. This study represents the first systematic analysis of the role of all RRs in V. cholerae pathogenesis and provides a foundation for understanding the signal transduction pathways controlling V. cholerae pathogenesis.
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