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Mikucki A, Kahler CM. Microevolution and Its Impact on Hypervirulence, Antimicrobial Resistance, and Vaccine Escape in Neisseria meningitidis. Microorganisms 2023; 11:3005. [PMID: 38138149 PMCID: PMC10745880 DOI: 10.3390/microorganisms11123005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2023] [Revised: 12/07/2023] [Accepted: 12/14/2023] [Indexed: 12/24/2023] Open
Abstract
Neisseria meningitidis is commensal of the human pharynx and occasionally invades the host, causing the life-threatening illness invasive meningococcal disease. The meningococcus is a highly diverse and adaptable organism thanks to natural competence, a propensity for recombination, and a highly repetitive genome. These mechanisms together result in a high level of antigenic variation to invade diverse human hosts and evade their innate and adaptive immune responses. This review explores the ways in which this diversity contributes to the evolutionary history and population structure of the meningococcus, with a particular focus on microevolution. It examines studies on meningococcal microevolution in the context of within-host evolution and persistent carriage; microevolution in the context of meningococcal outbreaks and epidemics; and the potential of microevolution to contribute to antimicrobial resistance and vaccine escape. A persistent theme is the idea that the process of microevolution contributes to the development of new hyperinvasive meningococcal variants. As such, microevolution in this species has significant potential to drive future public health threats in the form of hypervirulent, antibiotic-resistant, vaccine-escape variants. The implications of this on current vaccination strategies are explored.
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Affiliation(s)
- August Mikucki
- Marshall Centre for Infectious Diseases Research and Training, School of Biomedical Sciences, University of Western Australia, Perth, WA 6009, Australia;
- Wesfarmers Centre of Vaccines and Infectious Diseases, Telethon Kids Institute, University of Western Australia, Perth, WA 6009, Australia
| | - Charlene M. Kahler
- Marshall Centre for Infectious Diseases Research and Training, School of Biomedical Sciences, University of Western Australia, Perth, WA 6009, Australia;
- Wesfarmers Centre of Vaccines and Infectious Diseases, Telethon Kids Institute, University of Western Australia, Perth, WA 6009, Australia
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2
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Arenas J. Editorial: Pathogenic Neisseria: Pathogenicity, vaccines, and antibiotic resistance. Front Cell Infect Microbiol 2023; 12:1119244. [PMID: 36683679 PMCID: PMC9850228 DOI: 10.3389/fcimb.2022.1119244] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2022] [Accepted: 12/21/2022] [Indexed: 01/06/2023] Open
Affiliation(s)
- Jesús Arenas
- Unit of Microbiology and Immunology, Faculty of Veterinary, University of Zaragoza, Zaragoza, Spain
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3
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Bartelli NL, Passanisi VJ, Michalska K, Song K, Nhan DQ, Zhou H, Cuthbert BJ, Stols LM, Eschenfeldt WH, Wilson NG, Basra JS, Cortes R, Noorsher Z, Gabraiel Y, Poonen-Honig I, Seacord EC, Goulding CW, Low DA, Joachimiak A, Dahlquist FW, Hayes CS. Proteolytic processing induces a conformational switch required for antibacterial toxin delivery. Nat Commun 2022; 13:5078. [PMID: 36038560 PMCID: PMC9424206 DOI: 10.1038/s41467-022-32795-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2021] [Accepted: 08/12/2022] [Indexed: 02/08/2023] Open
Abstract
Many Gram-negative bacteria use CdiA effector proteins to inhibit the growth of neighboring competitors. CdiA transfers its toxic CdiA-CT region into the periplasm of target cells, where it is released through proteolytic cleavage. The N-terminal cytoplasm-entry domain of the CdiA-CT then mediates translocation across the inner membrane to deliver the C-terminal toxin domain into the cytosol. Here, we show that proteolysis not only liberates the CdiA-CT for delivery, but is also required to activate the entry domain for membrane translocation. Translocation function depends on precise cleavage after a conserved VENN peptide sequence, and the processed ∆VENN entry domain exhibits distinct biophysical and thermodynamic properties. By contrast, imprecisely processed CdiA-CT fragments do not undergo this transition and fail to translocate to the cytoplasm. These findings suggest that CdiA-CT processing induces a critical structural switch that converts the entry domain into a membrane-translocation competent conformation.
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Affiliation(s)
- Nicholas L Bartelli
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA, USA
| | - Victor J Passanisi
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA, USA
| | - Karolina Michalska
- Midwest Center for Structural Genomics, Argonne National Laboratory, Lemont, IL, USA
- Center for Structural Genomics of Infectious Diseases, University of Chicago, Chicago, IL, USA
- Structural Biology Center, X-ray Science Division, Argonne National Laboratory, Lemont, IL, USA
| | - Kiho Song
- Biomolecular Science and Engineering Program, University of California, Santa Barbara, CA, USA
| | - Dinh Q Nhan
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, CA, USA
| | - Hongjun Zhou
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA, USA
| | - Bonnie J Cuthbert
- Department of Molecular Biology & Biochemistry, University of California, Irvine, CA, USA
| | - Lucy M Stols
- Midwest Center for Structural Genomics, Argonne National Laboratory, Lemont, IL, USA
| | - William H Eschenfeldt
- Midwest Center for Structural Genomics, Argonne National Laboratory, Lemont, IL, USA
| | - Nicholas G Wilson
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA, USA
| | - Jesse S Basra
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA, USA
| | - Ricardo Cortes
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA, USA
| | - Zainab Noorsher
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA, USA
| | - Youssef Gabraiel
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA, USA
| | - Isaac Poonen-Honig
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA, USA
| | - Elizabeth C Seacord
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA, USA
| | - Celia W Goulding
- Department of Molecular Biology & Biochemistry, University of California, Irvine, CA, USA
- Pharmaceutical Sciences, University of California, Irvine, CA, USA
| | - David A Low
- Biomolecular Science and Engineering Program, University of California, Santa Barbara, CA, USA
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, CA, USA
| | - Andrzej Joachimiak
- Midwest Center for Structural Genomics, Argonne National Laboratory, Lemont, IL, USA
- Center for Structural Genomics of Infectious Diseases, University of Chicago, Chicago, IL, USA
- Structural Biology Center, X-ray Science Division, Argonne National Laboratory, Lemont, IL, USA
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL, USA
| | - Frederick W Dahlquist
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA, USA
- Biomolecular Science and Engineering Program, University of California, Santa Barbara, CA, USA
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, CA, USA
| | - Christopher S Hayes
- Biomolecular Science and Engineering Program, University of California, Santa Barbara, CA, USA.
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, CA, USA.
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4
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Talà A, Guerra F, Calcagnile M, Romano R, Resta SC, Paiano A, Chiariello M, Pizzolante G, Bucci C, Alifano P. HrpA anchors meningococci to the dynein motor and affects the balance between apoptosis and pyroptosis. J Biomed Sci 2022; 29:45. [PMID: 35765029 PMCID: PMC9241232 DOI: 10.1186/s12929-022-00829-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2022] [Accepted: 06/22/2022] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND In Neisseria meningitidis the HrpA/HrpB two-partner secretion system (TPS) was implicated in diverse functions including meningococcal competition, biofilm formation, adherence to epithelial cells, intracellular survival and vacuolar escape. These diverse functions could be attributed to distinct domains of secreted HrpA. METHODS A yeast two-hybrid screening, in vitro pull-down assay and immunofluorescence microscopy experiments were used to investigate the interaction between HrpA and the dynein light-chain, Tctex-type 1 (DYNLT1). In silico modeling was used to analyze HrpA structure. Western blot analysis was used to investigate apoptotic and pyroptotic markers. RESULTS The HrpA carboxy-terminal region acts as a manganese-dependent cell lysin, while the results of a yeast two-hybrid screening demonstrated that the HrpA middle region has the ability to bind the dynein light-chain, Tctex-type 1 (DYNLT1). This interaction was confirmed by in vitro pull-down assay and immunofluorescence microscopy experiments showing co-localization of N. meningitidis with DYNLT1 in infected epithelial cells. In silico modeling revealed that the HrpA-M interface interacting with the DYNLT1 has similarity with capsid proteins of neurotropic viruses that interact with the DYNLT1. Indeed, we found that HrpA plays a key role in infection of and meningococcal trafficking within neuronal cells, and is implicated in the modulation of the balance between apoptosis and pyroptosis. CONCLUSIONS Our findings revealed that N. meningitidis is able to effectively infect and survive in neuronal cells, and that this ability is dependent on HrpA, which establishes a direct protein-protein interaction with DYNLTI in these cells, suggesting that the HrpA interaction with dynein could be fundamental for N. meningitidis spreading inside the neurons. Moreover, we found that the balance between apoptotic and pyroptotic pathways is heavily affected by HrpA.
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Affiliation(s)
- Adelfia Talà
- Department of Biological and Environmental Sciences and Technologies (DiSTeBA), University of Salento, Via Provinciale Monteroni n. 165, 73100, Lecce, Italy
| | - Flora Guerra
- Department of Biological and Environmental Sciences and Technologies (DiSTeBA), University of Salento, Via Provinciale Monteroni n. 165, 73100, Lecce, Italy
| | - Matteo Calcagnile
- Department of Biological and Environmental Sciences and Technologies (DiSTeBA), University of Salento, Via Provinciale Monteroni n. 165, 73100, Lecce, Italy
| | - Roberta Romano
- Department of Biological and Environmental Sciences and Technologies (DiSTeBA), University of Salento, Via Provinciale Monteroni n. 165, 73100, Lecce, Italy
| | - Silvia Caterina Resta
- Department of Biological and Environmental Sciences and Technologies (DiSTeBA), University of Salento, Via Provinciale Monteroni n. 165, 73100, Lecce, Italy
| | - Aurora Paiano
- Department of Biological and Environmental Sciences and Technologies (DiSTeBA), University of Salento, Via Provinciale Monteroni n. 165, 73100, Lecce, Italy
| | - Mario Chiariello
- Core Research Laboratory-Siena, Institute for Cancer Research and Prevention (ISPRO), 53100, Siena, Italy.,Institute of Clinical Physiology (IFC), National Research Council (CNR), 53100, Siena, Italy
| | - Graziano Pizzolante
- Department of Biological and Environmental Sciences and Technologies (DiSTeBA), University of Salento, Via Provinciale Monteroni n. 165, 73100, Lecce, Italy
| | - Cecilia Bucci
- Department of Biological and Environmental Sciences and Technologies (DiSTeBA), University of Salento, Via Provinciale Monteroni n. 165, 73100, Lecce, Italy.
| | - Pietro Alifano
- Department of Biological and Environmental Sciences and Technologies (DiSTeBA), University of Salento, Via Provinciale Monteroni n. 165, 73100, Lecce, Italy.
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5
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Baerentsen R, Tang CM, Exley RM. Et tu, Neisseria? Conflicts of Interest Between Neisseria Species. Front Cell Infect Microbiol 2022; 12:913292. [PMID: 35811666 PMCID: PMC9263626 DOI: 10.3389/fcimb.2022.913292] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2022] [Accepted: 05/27/2022] [Indexed: 11/24/2022] Open
Abstract
Neisseria meningitidis and Neisseria gonorrhoeae are two obligate human pathogens that have evolved to be uniquely adapted to their host. The meningococcus is frequently carried asymptomatically in the nasopharynx, while gonococcal infection of the urogenital tract usually elicits a marked local inflammatory response. Other members of the Neisseria genus are abundant in the upper airway where they could engage in co-operative or competitive interactions with both these pathogens. Here, we briefly outline the potential sites of contact between Neisseria spp. in the body, with emphasis on the upper airway, and describe the growing yet circumstantial evidence for antagonism from carriage studies and human volunteer challenge models with Neisseria lactamica. Recent laboratory studies have characterized antagonistic mechanisms that enable competition between Neisseria species. Several of these mechanisms, including Multiple Adhesin family (Mafs), Two Partner Secretion Systems, and Type VI secretion system, involve direct contact between bacteria; the genetic organisation of these systems, and the domain structure of their effector molecules have striking similarities. Additionally, DNA from one species of Neisseria can be toxic to another species, following uptake. More research is needed to define the full repertoire of antagonistic mechanisms in Neisseria spp., their distribution in strains, their range of activity, and contribution to survival in vivo. Understanding the targets of effectors could reveal how antagonistic relationships between close relatives shape subsequent interactions between pathogens and their hosts.
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6
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Mikucki A, McCluskey NR, Kahler CM. The Host-Pathogen Interactions and Epicellular Lifestyle of Neisseria meningitidis. Front Cell Infect Microbiol 2022; 12:862935. [PMID: 35531336 PMCID: PMC9072670 DOI: 10.3389/fcimb.2022.862935] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2022] [Accepted: 02/28/2022] [Indexed: 01/17/2023] Open
Abstract
Neisseria meningitidis is a gram-negative diplococcus and a transient commensal of the human nasopharynx. It shares and competes for this niche with a number of other Neisseria species including N. lactamica, N. cinerea and N. mucosa. Unlike these other members of the genus, N. meningitidis may become invasive, crossing the epithelium of the nasopharynx and entering the bloodstream, where it rapidly proliferates causing a syndrome known as Invasive Meningococcal Disease (IMD). IMD progresses rapidly to cause septic shock and meningitis and is often fatal despite aggressive antibiotic therapy. While many of the ways in which meningococci survive in the host environment have been well studied, recent insights into the interactions between N. meningitidis and the epithelial, serum, and endothelial environments have expanded our understanding of how IMD develops. This review seeks to incorporate recent work into the established model of pathogenesis. In particular, we focus on the competition that N. meningitidis faces in the nasopharynx from other Neisseria species, and how the genetic diversity of the meningococcus contributes to the wide range of inflammatory and pathogenic potentials observed among different lineages.
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Affiliation(s)
- August Mikucki
- Marshall Centre for Infectious Diseases Research and Training, School of Biomedical Sciences, University of Western Australia, Perth, WA, Australia
| | - Nicolie R. McCluskey
- Marshall Centre for Infectious Diseases Research and Training, School of Biomedical Sciences, University of Western Australia, Perth, WA, Australia
- College of Science, Health, Engineering and Education, Telethon Kids Institute, Murdoch University, Perth, WA, Australia
| | - Charlene M. Kahler
- Marshall Centre for Infectious Diseases Research and Training, School of Biomedical Sciences, University of Western Australia, Perth, WA, Australia
- *Correspondence: Charlene M. Kahler,
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7
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Mullally CA, Mikucki A, Wise MJ, Kahler CM. Modelling evolutionary pathways for commensalism and hypervirulence in Neisseria meningitidis. Microb Genom 2021; 7. [PMID: 34704920 PMCID: PMC8627216 DOI: 10.1099/mgen.0.000662] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Neisseria meningitidis, the meningococcus, resides exclusively in humans and causes invasive meningococcal disease (IMD). The population of N. meningitidis is structured into stable clonal complexes by limited horizontal recombination in this naturally transformable species. N. meningitidis is an opportunistic pathogen, with some clonal complexes, such as cc53, effectively acting as commensal colonizers, while other genetic lineages, such as cc11, are rarely colonizers but are over-represented in IMD and are termed hypervirulent. This study examined theoretical evolutionary pathways for pathogenic and commensal lineages by examining the prevalence of horizontally acquired genomic islands (GIs) and loss-of-function (LOF) mutations. Using a collection of 4850 genomes from the BIGSdb database, we identified 82 GIs in the pan-genome of 11 lineages (10 hypervirulent and one commensal lineage). A new computational tool, Phaser, was used to identify frameshift mutations, which were examined for statistically significant association with genetic lineage. Phaser identified a total of 144 frameshift loci of which 105 were shown to have a statistically significant non-random distribution in phase status. The 82 GIs, but not the LOF loci, were associated with genetic lineage and invasiveness using the disease carriage ratio metric. These observations have been integrated into a new model that infers the early events of the evolution of the human adapted meningococcus. These pathways are enriched for GIs that are involved in modulating attachment to the host, growth rate, iron uptake and toxin expression which are proposed to increase competition within the meningococcal population for the limited environmental niche of the human nasopharynx. We surmise that competition for the host mucosal surface with the nasopharyngeal microbiome has led to the selection of isolates with traits that enable access to cell types (non-phagocytic and phagocytic) in the submucosal tissues leading to an increased risk for IMD.
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Affiliation(s)
- Christopher A. Mullally
- The Marshall Center for Infectious Diseases Research and Training, School of Biomedical Science, University of Western Australia, Perth, Australia
| | - August Mikucki
- The Marshall Center for Infectious Diseases Research and Training, School of Biomedical Science, University of Western Australia, Perth, Australia
| | - Michael J. Wise
- The Marshall Center for Infectious Diseases Research and Training, School of Biomedical Science, University of Western Australia, Perth, Australia
- School of Physics, Mathematics and Computing, University of Western Australia, Perth, Australia
| | - Charlene M. Kahler
- The Marshall Center for Infectious Diseases Research and Training, School of Biomedical Science, University of Western Australia, Perth, Australia
- Telethon Kids Institute, Perth Children’s Hospital, Perth, Australia
- *Correspondence: Charlene M. Kahler,
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Lipidation of Class IV CdiA Effector Proteins Promotes Target Cell Recognition during Contact-Dependent Growth Inhibition. mBio 2021; 12:e0253021. [PMID: 34634941 PMCID: PMC8510554 DOI: 10.1128/mbio.02530-21] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Contact-dependent growth inhibition (CDI) systems enable the direct transfer of protein toxins between competing Gram-negative bacteria. CDI+ strains produce cell surface CdiA effector proteins that bind specific receptors on neighboring bacteria to initiate toxin delivery. Three classes of CdiA effectors that recognize different outer membrane protein receptors have been characterized in Escherichia coli to date. Here, we describe a fourth effector class that uses the lipopolysaccharide (LPS) core as a receptor to identify target bacteria. Selection for CDI-resistant target cells yielded waaF and waaP “deep-rough” mutants, which are unable to synthesize the full LPS core. The CDI resistance phenotypes of other waa mutants suggest that phosphorylated inner-core heptose residues form a critical CdiA recognition epitope. Class IV cdi loci also encode putative lysyl acyltransferases (CdiC) that are homologous to enzymes that lipidate repeats-in-toxin (RTX) cytolysins. We found that catalytically active CdiC is required for full target cell killing activity, and we provide evidence that the acyltransferase appends 3-hydroxydecanoate to a specific Lys residue within the CdiA receptor-binding domain. We propose that the lipid moiety inserts into the hydrophobic leaflet of lipid A to anchor CdiA interactions with the core oligosaccharide. Thus, LPS-binding CDI systems appear to have co-opted an RTX toxin-activating acyltransferase to increase the affinity of CdiA effectors for the target cell outer membrane.
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9
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Arenas J, Catón L, van den Hoeven T, de Maat V, Cruz Herrero J, Tommassen J. The outer-membrane protein MafA of Neisseria meningitidis constitutes a novel protein secretion pathway specific for the fratricide protein MafB. Virulence 2021; 11:1701-1715. [PMID: 33315509 PMCID: PMC7738311 DOI: 10.1080/21505594.2020.1851940] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
MafB proteins are toxins secreted by Neisseria spp. which are involved in interbacterial competition. Their secretion mechanism has so far not been elucidated. Each strain can produce several MafB variants. On the chromosome, the mafB genes are localized on genomic islands also containing mafA genes. MafA proteins have a role in virulence with reported activities in adhesion and transcytosis of pathogenic Neisseria, a priori unrelated to MafB activities. In this study, we investigated the possible involvement of MafA in the transport of MafB across the outer membrane of Neisseria meningitidis. In wild-type strains, proteolytic fragments of MafB proteins were detected in the extracellular medium. In the absence of MafA, secretion was abrogated, and, in the case of MafBI, full-length and truncated polypeptides were detected inside the cells and inside outer-membrane vesicles. MafBI secretion required its cognate MafA, whereas MafBIII could use any MafA. Heterologous expression in Escherichia coli showed that MafBIII is transported to a cell-surface-exposed, i.e. protease-accessible, location in a MafA-dependent way. MafA itself was found to be localized to the outer membrane, forming large oligomeric complexes. As homologs were found in diverse bacteria, the Maf system represents a new protein secretion system in Gram-negative bacteria.
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Affiliation(s)
- Jesús Arenas
- Section Molecular Microbiology, Department of Biology, Utrecht University , Utrecht, Netherlands.,Unit of Microbiology and Immunology, Faculty of Veterinary, University of Zaragoza , Zaragoza, Spain
| | - Laura Catón
- Section Molecular Microbiology, Department of Biology, Utrecht University , Utrecht, Netherlands
| | - Tom van den Hoeven
- Section Molecular Microbiology, Department of Biology, Utrecht University , Utrecht, Netherlands
| | - Vincent de Maat
- Section Molecular Microbiology, Department of Biology, Utrecht University , Utrecht, Netherlands
| | - Juan Cruz Herrero
- Section Molecular Microbiology, Department of Biology, Utrecht University , Utrecht, Netherlands
| | - Jan Tommassen
- Section Molecular Microbiology, Department of Biology, Utrecht University , Utrecht, Netherlands
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10
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Biofilms as Promoters of Bacterial Antibiotic Resistance and Tolerance. Antibiotics (Basel) 2020; 10:antibiotics10010003. [PMID: 33374551 PMCID: PMC7822488 DOI: 10.3390/antibiotics10010003] [Citation(s) in RCA: 167] [Impact Index Per Article: 41.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Revised: 12/15/2020] [Accepted: 12/19/2020] [Indexed: 12/12/2022] Open
Abstract
Multidrug resistant bacteria are a global threat for human and animal health. However, they are only part of the problem of antibiotic failure. Another bacterial strategy that contributes to their capacity to withstand antimicrobials is the formation of biofilms. Biofilms are associations of microorganisms embedded a self-produced extracellular matrix. They create particular environments that confer bacterial tolerance and resistance to antibiotics by different mechanisms that depend upon factors such as biofilm composition, architecture, the stage of biofilm development, and growth conditions. The biofilm structure hinders the penetration of antibiotics and may prevent the accumulation of bactericidal concentrations throughout the entire biofilm. In addition, gradients of dispersion of nutrients and oxygen within the biofilm generate different metabolic states of individual cells and favor the development of antibiotic tolerance and bacterial persistence. Furthermore, antimicrobial resistance may develop within biofilms through a variety of mechanisms. The expression of efflux pumps may be induced in various parts of the biofilm and the mutation frequency is induced, while the presence of extracellular DNA and the close contact between cells favor horizontal gene transfer. A deep understanding of the mechanisms by which biofilms cause tolerance/resistance to antibiotics helps to develop novel strategies to fight these infections.
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11
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Ruhe ZC, Low DA, Hayes CS. Polymorphic Toxins and Their Immunity Proteins: Diversity, Evolution, and Mechanisms of Delivery. Annu Rev Microbiol 2020; 74:497-520. [PMID: 32680451 DOI: 10.1146/annurev-micro-020518-115638] [Citation(s) in RCA: 57] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
All bacteria must compete for growth niches and other limited environmental resources. These existential battles are waged at several levels, but one common strategy entails the transfer of growth-inhibitory protein toxins between competing cells. These antibacterial effectors are invariably encoded with immunity proteins that protect cells from intoxication by neighboring siblings. Several effector classes have been described, each designed to breach the cell envelope of target bacteria. Although effector architectures and export pathways tend to be clade specific, phylogenetically distant species often deploy closely related toxin domains. Thus, diverse competition systems are linked through a common reservoir of toxin-immunity pairs that is shared via horizontal gene transfer. These toxin-immunity protein pairs are extraordinarily diverse in sequence, and this polymorphism underpins an important mechanism of self/nonself discrimination in bacteria. This review focuses on the structures, functions, and delivery mechanisms of polymorphic toxin effectors that mediate bacterial competition.
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Affiliation(s)
- Zachary C Ruhe
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, California 93106, USA;
| | - David A Low
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, California 93106, USA; .,Biomolecular Science and Engineering Program, University of California, Santa Barbara, California 93106, USA
| | - Christopher S Hayes
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, California 93106, USA; .,Biomolecular Science and Engineering Program, University of California, Santa Barbara, California 93106, USA
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12
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A comparative genomics approach identifies contact-dependent growth inhibition as a virulence determinant. Proc Natl Acad Sci U S A 2020; 117:6811-6821. [PMID: 32156726 DOI: 10.1073/pnas.1919198117] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Emerging evidence suggests the Pseudomonas aeruginosa accessory genome is enriched with uncharacterized virulence genes. Identification and characterization of such genes may reveal novel pathogenic mechanisms used by particularly virulent isolates. Here, we utilized a mouse bacteremia model to quantify the virulence of 100 individual P. aeruginosa bloodstream isolates and performed whole-genome sequencing to identify accessory genomic elements correlated with increased bacterial virulence. From this work, we identified a specific contact-dependent growth inhibition (CDI) system enriched among highly virulent P. aeruginosa isolates. CDI systems contain a large exoprotein (CdiA) with a C-terminal toxin (CT) domain that can vary between different isolates within a species. Prior work has revealed that delivery of a CdiA-CT domain upon direct cell-to-cell contact can inhibit replication of a susceptible target bacterium. Aside from mediating interbacterial competition, we observed our virulence-associated CdiA-CT domain to promote toxicity against mammalian cells in culture and lethality during mouse bacteremia. Structural and functional studies revealed this CdiA-CT domain to have in vitro tRNase activity, and mutations that abrogated this tRNAse activity in vitro also attenuated virulence. Furthermore, CdiA contributed to virulence in mice even in the absence of contact-dependent signaling. Overall, our findings indicate that this P. aeruginosa CDI system functions as both an interbacterial inhibition system and a bacterial virulence factor against a mammalian host. These findings provide an impetus for continued studies into the complex role of CDI systems in P. aeruginosa pathogenesis.
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13
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Convergent Evolution of the Barnase/EndoU/Colicin/RelE (BECR) Fold in Antibacterial tRNase Toxins. Structure 2019; 27:1660-1674.e5. [PMID: 31515004 DOI: 10.1016/j.str.2019.08.010] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2019] [Revised: 08/03/2019] [Accepted: 08/20/2019] [Indexed: 11/20/2022]
Abstract
Contact-dependent growth inhibition (CDI) is a form of interbacterial competition mediated by CdiB-CdiA two-partner secretion systems. CdiA effector proteins carry polymorphic C-terminal toxin domains (CdiA-CT), which are neutralized by specific CdiI immunity proteins to prevent self-inhibition. Here, we present the crystal structures of CdiA-CT⋅CdiI complexes from Klebsiella pneumoniae 342 and Escherichia coli 3006. The toxins adopt related folds that resemble the ribonuclease domain of colicin D, and both are isoacceptor-specific tRNases that cleave the acceptor stem of deacylated tRNAGAUIle. Although the toxins are similar in structure and substrate specificity, CdiA-CTKp342 activity requires translation factors EF-Tu and EF-Ts, whereas CdiA-CTEC3006 is intrinsically active. Furthermore, the corresponding immunity proteins are unrelated in sequence and structure. CdiIKp342 forms a dimeric β sandwich, whereas CdiIEC3006 is an α-solenoid monomer. Given that toxin-immunity genes co-evolve as linked pairs, these observations suggest that the similarities in toxin structure and activity reflect functional convergence.
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14
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Coureuil M, Jamet A, Bille E, Lécuyer H, Bourdoulous S, Nassif X. Molecular interactions between Neisseria meningitidis and its human host. Cell Microbiol 2019; 21:e13063. [PMID: 31167044 PMCID: PMC6899865 DOI: 10.1111/cmi.13063] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2019] [Revised: 05/21/2019] [Accepted: 05/30/2019] [Indexed: 02/06/2023]
Abstract
Neisseria meningitidis is a Gram‐negative bacterium that asymptomatically colonises the nasopharynx of humans. For an unknown reason, N. meningitidis can cross the nasopharyngeal barrier and invade the bloodstream where it becomes one of the most harmful extracellular bacterial pathogen. This infectious cycle involves the colonisation of two different environments. (a) In the nasopharynx, N. meningitidis grow on the top of mucus‐producing epithelial cells surrounded by a complex microbiota. To survive and grow in this challenging environment, the meningococcus expresses specific virulence factors such as polymorphic toxins and MDAΦ. (b) Meningococci have the ability to survive in the extra cellular fluids including blood and cerebrospinal fluid. The interaction of N. meningitidis with human endothelial cells leads to the formation of typical microcolonies that extend overtime and promote vascular injury, disseminated intravascular coagulation, and acute inflammation. In this review, we will focus on the interplay between N. meningitidis and these two different niches at the cellular and molecular level and discuss the use of inhibitors of piliation as a potent therapeutic approach.
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Affiliation(s)
- Mathieu Coureuil
- Inserm, Institut Necker Enfants Malades, U1151, Paris, France.,Université de Paris, UMR_S 1151, Paris, France.,CNRS, UMR 8253, Paris, France
| | - Anne Jamet
- Inserm, Institut Necker Enfants Malades, U1151, Paris, France.,Université de Paris, UMR_S 1151, Paris, France.,CNRS, UMR 8253, Paris, France.,Assistance Publique - Hôpitaux de Paris, Hôpital Necker Enfants Malades, Paris, France
| | - Emmanuelle Bille
- Inserm, Institut Necker Enfants Malades, U1151, Paris, France.,Université de Paris, UMR_S 1151, Paris, France.,CNRS, UMR 8253, Paris, France.,Assistance Publique - Hôpitaux de Paris, Hôpital Necker Enfants Malades, Paris, France
| | - Hervé Lécuyer
- Inserm, Institut Necker Enfants Malades, U1151, Paris, France.,Université de Paris, UMR_S 1151, Paris, France.,CNRS, UMR 8253, Paris, France.,Assistance Publique - Hôpitaux de Paris, Hôpital Necker Enfants Malades, Paris, France
| | - Sandrine Bourdoulous
- Université de Paris, UMR_S 1151, Paris, France.,Inserm, U1016, Institut Cochin, Paris, France.,CNRS, UMR8104, Paris, France
| | - Xavier Nassif
- Inserm, Institut Necker Enfants Malades, U1151, Paris, France.,Université de Paris, UMR_S 1151, Paris, France.,CNRS, UMR 8253, Paris, France.,Assistance Publique - Hôpitaux de Paris, Hôpital Necker Enfants Malades, Paris, France
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15
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De Gregorio E, Zarrilli R, Di Nocera PP. Contact-dependent growth inhibition systems in Acinetobacter. Sci Rep 2019; 9:154. [PMID: 30655547 PMCID: PMC6336857 DOI: 10.1038/s41598-018-36427-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2018] [Accepted: 11/21/2018] [Indexed: 11/09/2022] Open
Abstract
In bacterial contact-dependent growth inhibition (CDI) systems, CdiA proteins are exported to the outer membrane by cognate CdiB proteins. CdiA binds to receptors on susceptible bacteria and subsequently delivers its C-terminal toxin domain (CdiA-CT) into neighbouring target cells. Whereas self bacteria produce CdiI antitoxins, non-self bacteria lack antitoxins and are therefore inhibited in their growth by CdiA. In silico surveys of pathogenic Acinetobacter genomes have enabled us to identify >40 different CDI systems, which we sorted into two distinct groups. Type-II CdiAs are giant proteins (3711 to 5733 residues) with long arrays of 20-mer repeats. Type-I CdiAs are smaller (1900-2400 residues), lack repeats and feature central heterogeneity (HET) regions, that vary in size and sequence and can be exchanged between CdiA proteins. HET regions in most type-I proteins confer the ability to adopt a coiled-coil conformation. CdiA-CT and pretoxin modules differ significantly between type-I and type-II CdiAs. Moreover, type-II genes only have remnants of genes in their 3' end regions that have been displaced by the insertion of novel cdi sequences. Type-I and type-II CDI systems are equally abundant in A. baumannii, whereas A. pittii and A. nosocomialis predominantly feature type-I and type-II systems, respectively.
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Affiliation(s)
- Eliana De Gregorio
- Dipartimento di Medicina Molecolare e Biotecnologie Mediche, Università Federico II, Via Sergio Pansini 5, Naples, 80131, Italy.,Dipartimento di Sanità Pubblica, Università Federico II, Via Sergio Pansini 5, 80131, Naples, Italy
| | - Raffaele Zarrilli
- Dipartimento di Sanità Pubblica, Università Federico II, Via Sergio Pansini 5, 80131, Naples, Italy.
| | - Pier Paolo Di Nocera
- Dipartimento di Medicina Molecolare e Biotecnologie Mediche, Università Federico II, Via Sergio Pansini 5, Naples, 80131, Italy.
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16
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Three Distinct Contact-Dependent Growth Inhibition Systems Mediate Interbacterial Competition by the Cystic Fibrosis Pathogen Burkholderia dolosa. J Bacteriol 2018; 200:JB.00428-18. [PMID: 30150233 DOI: 10.1128/jb.00428-18] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2018] [Accepted: 08/23/2018] [Indexed: 02/08/2023] Open
Abstract
The respiratory tracts of individuals afflicted with cystic fibrosis (CF) harbor complex polymicrobial communities. By an unknown mechanism, species of the Gram-negative Burkholderia cepacia complex, such as Burkholderia dolosa, can displace other bacteria in the CF lung, causing cepacia syndrome, which has a poor prognosis. The genome of B dolosa strain AU0158 (BdAU0158) contains three loci that are predicted to encode contact-dependent growth inhibition (CDI) systems. CDI systems function by translocating the toxic C terminus of a large exoprotein directly into target cells, resulting in growth inhibition or death unless the target cells produce a cognate immunity protein. We demonstrate here that each of the three bcpAIOB loci in BdAU0158 encodes a distinct CDI system that mediates interbacterial competition in an allele-specific manner. While only two of the three bcpAIOB loci were expressed under the in vitro conditions tested, the third conferred immunity under these conditions due to the presence of an internal promoter driving expression of the bcpI gene. One BdAU0158 bcpAIOB allele is highly similar to bcpAIOB in Burkholderia thailandensis strain E264 (BtE264), and we showed that their BcpI proteins are functionally interchangeable, but contact-dependent signaling (CDS) phenotypes were not observed in BdAU0158. Our findings suggest that the CDI systems of BdAU0158 may provide this pathogen an ecological advantage during polymicrobial infections of the CF respiratory tract.IMPORTANCE Human-associated polymicrobial communities can promote health and disease, and interbacterial interactions influence the microbial ecology of such communities. Polymicrobial infections of the cystic fibrosis respiratory tract impair lung function and lead to the death of individuals suffering from this disorder; therefore, a greater understanding of these microbial communities is necessary for improving treatment strategies. Bacteria utilize contact-dependent growth inhibition systems to kill neighboring competitors and maintain their niche within multicellular communities. Several cystic fibrosis pathogens have the potential to gain an ecological advantage during infection via contact-dependent growth inhibition systems, including Burkholderia dolosa Our research is significant, as it has identified three functional contact-dependent growth inhibition systems in B dolosa that may provide this pathogen a competitive advantage during polymicrobial infections.
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17
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Michalska K, Quan Nhan D, Willett JLE, Stols LM, Eschenfeldt WH, Jones AM, Nguyen JY, Koskiniemi S, Low DA, Goulding CW, Joachimiak A, Hayes CS. Functional plasticity of antibacterial EndoU toxins. Mol Microbiol 2018; 109:509-527. [PMID: 29923643 PMCID: PMC6173971 DOI: 10.1111/mmi.14007] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/15/2018] [Indexed: 01/05/2023]
Abstract
Bacteria use several different secretion systems to deliver toxic EndoU ribonucleases into neighboring cells. Here, we present the first structure of a prokaryotic EndoU toxin in complex with its cognate immunity protein. The contact-dependent growth inhibition toxin CdiA-CTSTECO31 from Escherichia coli STEC_O31 adopts the eukaryotic EndoU fold and shares greatest structural homology with the nuclease domain of coronavirus Nsp15. The toxin contains a canonical His-His-Lys catalytic triad in the same arrangement as eukaryotic EndoU domains, but lacks the uridylate-specific ribonuclease activity that characterizes the superfamily. Comparative sequence analysis indicates that bacterial EndoU domains segregate into at least three major clades based on structural variations in the N-terminal subdomain. Representative EndoU nucleases from clades I and II degrade tRNA molecules with little specificity. In contrast, CdiA-CTSTECO31 and other clade III toxins are specific anticodon nucleases that cleave tRNAGlu between nucleotides C37 and m2 A38. These findings suggest that the EndoU fold is a versatile scaffold for the evolution of novel substrate specificities. Such functional plasticity may account for the widespread use of EndoU effectors by diverse inter-bacterial toxin delivery systems.
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Affiliation(s)
- Karolina Michalska
- Midwest Center for Structural Genomics, Argonne National Laboratory, Argonne, IL, USA.,Structural Biology Center, Biosciences Division, Argonne National Laboratory, Argonne, IL, USA
| | - Dinh Quan Nhan
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, CA, USA
| | - Julia L E Willett
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, CA, USA
| | - Lucy M Stols
- Midwest Center for Structural Genomics, Argonne National Laboratory, Argonne, IL, USA
| | - William H Eschenfeldt
- Midwest Center for Structural Genomics, Argonne National Laboratory, Argonne, IL, USA
| | - Allison M Jones
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, CA, USA
| | - Josephine Y Nguyen
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, CA, USA
| | - Sanna Koskiniemi
- Department of Cell and Molecular Biology, Uppsala University, Uppsala, Sweden
| | - David A Low
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, CA, USA.,Biomolecular Science and Engineering Program, University of California, Santa Barbara, CA, USA
| | - Celia W Goulding
- Department of Molecular Biology & Biochemistry, University of California, Irvine, CA, USA.,Pharmaceutical Sciences, University of California, Irvine, CA, USA
| | - Andrzej Joachimiak
- Midwest Center for Structural Genomics, Argonne National Laboratory, Argonne, IL, USA.,Structural Biology Center, Biosciences Division, Argonne National Laboratory, Argonne, IL, USA.,Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL, USA
| | - Christopher S Hayes
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, CA, USA.,Biomolecular Science and Engineering Program, University of California, Santa Barbara, CA, USA
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18
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Michalska K, Gucinski GC, Garza-Sánchez F, Johnson PM, Stols LM, Eschenfeldt WH, Babnigg G, Low DA, Goulding CW, Joachimiak A, Hayes CS. Structure of a novel antibacterial toxin that exploits elongation factor Tu to cleave specific transfer RNAs. Nucleic Acids Res 2017; 45:10306-10320. [PMID: 28973472 PMCID: PMC5737660 DOI: 10.1093/nar/gkx700] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2017] [Accepted: 07/29/2017] [Indexed: 12/23/2022] Open
Abstract
Contact-dependent growth inhibition (CDI) is a mechanism of inter-cellular competition in which Gram-negative bacteria exchange polymorphic toxins using type V secretion systems. Here, we present structures of the CDI toxin from Escherichia coli NC101 in ternary complex with its cognate immunity protein and elongation factor Tu (EF-Tu). The toxin binds exclusively to domain 2 of EF-Tu, partially overlapping the site that interacts with the 3'-end of aminoacyl-tRNA (aa-tRNA). The toxin exerts a unique ribonuclease activity that cleaves the single-stranded 3'-end from tRNAs that contain guanine discriminator nucleotides. EF-Tu is required to support this tRNase activity in vitro, suggesting the toxin specifically cleaves substrate in the context of GTP·EF-Tu·aa-tRNA complexes. However, superimposition of the toxin domain onto previously solved GTP·EF-Tu·aa-tRNA structures reveals potential steric clashes with both aa-tRNA and the switch I region of EF-Tu. Further, the toxin induces conformational changes in EF-Tu, displacing a β-hairpin loop that forms a critical salt-bridge contact with the 3'-terminal adenylate of aa-tRNA. Together, these observations suggest that the toxin remodels GTP·EF-Tu·aa-tRNA complexes to free the 3'-end of aa-tRNA for entry into the nuclease active site.
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Affiliation(s)
- Karolina Michalska
- Midwest Center for Structural Genomics, Biosciences Division, Argonne National Laboratory, Argonne, IL 60439, USA.,Structural Biology Center, Biosciences Division, Argonne National Laboratory, Argonne, IL 60439, USA
| | - Grant C Gucinski
- Biomolecular Science and Engineering Program, University of California, Santa Barbara, CA 93106-9625, USA
| | - Fernando Garza-Sánchez
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, CA 93106-9625, USA
| | - Parker M Johnson
- Department of Molecular Biology and Biochemistry, University of California, Irvine, CA 92697, USA
| | - Lucy M Stols
- Midwest Center for Structural Genomics, Biosciences Division, Argonne National Laboratory, Argonne, IL 60439, USA
| | - William H Eschenfeldt
- Midwest Center for Structural Genomics, Biosciences Division, Argonne National Laboratory, Argonne, IL 60439, USA
| | - Gyorgy Babnigg
- Midwest Center for Structural Genomics, Biosciences Division, Argonne National Laboratory, Argonne, IL 60439, USA
| | - David A Low
- Biomolecular Science and Engineering Program, University of California, Santa Barbara, CA 93106-9625, USA.,Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, CA 93106-9625, USA
| | - Celia W Goulding
- Department of Molecular Biology and Biochemistry, University of California, Irvine, CA 92697, USA.,Department of Pharmaceutical Sciences, University of California, Irvine, CA 92697, USA
| | - Andrzej Joachimiak
- Midwest Center for Structural Genomics, Biosciences Division, Argonne National Laboratory, Argonne, IL 60439, USA.,Structural Biology Center, Biosciences Division, Argonne National Laboratory, Argonne, IL 60439, USA.,Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL 60637, USA
| | - Christopher S Hayes
- Biomolecular Science and Engineering Program, University of California, Santa Barbara, CA 93106-9625, USA.,Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, CA 93106-9625, USA
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19
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Garcia EC. Contact-dependent interbacterial toxins deliver a message. Curr Opin Microbiol 2017; 42:40-46. [PMID: 29078204 DOI: 10.1016/j.mib.2017.09.011] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2017] [Revised: 09/06/2017] [Accepted: 09/14/2017] [Indexed: 02/04/2023]
Abstract
Both Gram-negative and Gram-positive organisms harbor systems for delivering toxins to neighboring bacteria upon direct cell contact. These systems, typified by type VI secretion (T6S) and contact-dependent growth inhibition (CDI) systems, are defined by their ability to mediate interbacterial competition in vitro, while their biological roles have remained uncertain. Recent research into the mechanisms of toxin delivery and activity, as well as investigation of contact-dependent toxin function during relevant biological processes, has offered insight into how interbacterial competition might work outside of the laboratory. Furthermore, non-competitive roles for contact-dependent toxin delivery systems, including interbacterial signal transduction, have been described. This review suggests that contact-dependent toxin delivery systems that exhibit functions beyond interbacterial competition are probably more common than currently appreciated.
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Affiliation(s)
- Erin C Garcia
- Department of Microbiology, Immunology, and Molecular Genetics, University of Kentucky, Lexington, KY 40536, United States.
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20
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Tommassen J, Arenas J. Biological Functions of the Secretome of Neisseria meningitidis. Front Cell Infect Microbiol 2017; 7:256. [PMID: 28670572 PMCID: PMC5472700 DOI: 10.3389/fcimb.2017.00256] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2017] [Accepted: 05/29/2017] [Indexed: 11/13/2022] Open
Abstract
Neisseria meningitidis is a Gram-negative bacterial pathogen that normally resides as a commensal in the human nasopharynx but occasionally causes disease with high mortality and morbidity. To interact with its environment, it transports many proteins across the outer membrane to the bacterial cell surface and into the extracellular medium for which it deploys the common and well-characterized autotransporter, two-partner and type I secretion mechanisms, as well as a recently discovered pathway for the surface exposure of lipoproteins. The surface-exposed and secreted proteins serve roles in host-pathogen interactions, including adhesion to host cells and extracellular matrix proteins, evasion of nutritional immunity imposed by iron-binding proteins of the host, prevention of complement activation, neutralization of antimicrobial peptides, degradation of immunoglobulins, and permeabilization of epithelial layers. Furthermore, they have roles in interbacterial interactions, including the formation and dispersal of biofilms and the suppression of the growth of bacteria competing for the same niche. Here, we will review the protein secretion systems of N. meningitidis and focus on the functions of the secreted proteins.
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Affiliation(s)
- Jan Tommassen
- Department of Molecular Microbiology and Institute of Biomembranes, Utrecht UniversityUtrecht, Netherlands
| | - Jesús Arenas
- Department of Molecular Microbiology and Institute of Biomembranes, Utrecht UniversityUtrecht, Netherlands
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21
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Can't you hear me knocking: contact-dependent competition and cooperation in bacteria. Emerg Top Life Sci 2017; 1:75-83. [PMID: 29085916 DOI: 10.1042/etls20160019] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Microorganisms are in constant competition for growth niches and environmental resources. In Gram-negative bacteria, contact-dependent growth inhibition (CDI) systems link the fate of one cell with its immediate neighbor through touch-dependent, receptor-mediated toxin delivery. Though discovered for their ability to confer a competitive growth advantage, CDI systems also play significant roles in inter-sibling cooperation, promoting both auto-aggregation and biofilm formation. In this review, we detail the mechanisms of CDI toxin delivery and consider how toxin exchange between isogenic sibling cells could regulate gene expression.
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22
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Harding CM, Pulido MR, Di Venanzio G, Kinsella RL, Webb AI, Scott NE, Pachón J, Feldman MF. Pathogenic Acinetobacter species have a functional type I secretion system and contact-dependent inhibition systems. J Biol Chem 2017; 292:9075-9087. [PMID: 28373284 DOI: 10.1074/jbc.m117.781575] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2017] [Revised: 03/31/2017] [Indexed: 01/09/2023] Open
Abstract
Pathogenic Acinetobacter species, including Acinetobacter baumannii and Acinetobacter nosocomialis, are opportunistic human pathogens of increasing relevance worldwide. Although their mechanisms of drug resistance are well studied, the virulence factors that govern Acinetobacter pathogenesis are incompletely characterized. Here we define the complete secretome of A. nosocomialis strain M2 in minimal medium and demonstrate that pathogenic Acinetobacter species produce both a functional type I secretion system (T1SS) and a contact-dependent inhibition (CDI) system. Using bioinformatics, quantitative proteomics, and mutational analyses, we show that Acinetobacter uses its T1SS for exporting two putative T1SS effectors, an Repeats-in-Toxin (RTX)-serralysin-like toxin, and the biofilm-associated protein (Bap). Moreover, we found that mutation of any component of the T1SS system abrogated type VI secretion activity under nutrient-limited conditions, indicating a previously unrecognized cross-talk between these two systems. We also demonstrate that the Acinetobacter T1SS is required for biofilm formation. Last, we show that both A. nosocomialis and A. baumannii produce functioning CDI systems that mediate growth inhibition of sister cells lacking the cognate immunity protein. The Acinetobacter CDI systems are widely distributed across pathogenic Acinetobacter species, with many A. baumannii isolates harboring two distinct CDI systems. Collectively, these data demonstrate the power of differential, quantitative proteomics approaches to study secreted proteins, define the role of previously uncharacterized protein export systems, and observe cross-talk between secretion systems in the pathobiology of medically relevant Acinetobacter species.
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Affiliation(s)
- Christian M Harding
- From the Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Marina R Pulido
- From the Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri 63110.,the Unit of Infectious Diseases, Microbiology, and Preventive Medicine and Biomedical Institute of Seville, University Hospital Virgen del Rocío/Consejo Superior de Investigaciones Científicas, University of Sevilla, 41004 Seville, Spain
| | - Gisela Di Venanzio
- From the Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Rachel L Kinsella
- From the Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri 63110.,the Department of Biological Sciences, University of Alberta, Edmonton, Alberta T6G 2R3, Canada
| | - Andrew I Webb
- the Walter and Eliza Hall Institute of Medical Research, Parkville, Melbourne, Victoria 3052, Australia.,the Department of Medical Biology, University of Melbourne, Parkville, Victoria 3050, Australia, and
| | - Nichollas E Scott
- the Department of Microbiology and Immunology, Doherty Institute, University of Melbourne, Melbourne, Victoria 3000, Australia
| | - Jerónimo Pachón
- the Unit of Infectious Diseases, Microbiology, and Preventive Medicine and Biomedical Institute of Seville, University Hospital Virgen del Rocío/Consejo Superior de Investigaciones Científicas, University of Sevilla, 41004 Seville, Spain
| | - Mario F Feldman
- From the Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri 63110,
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23
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Abstract
Contact-dependent growth inhibition (CDI) systems encode CdiA effectors, which bind to specific receptors on neighboring bacteria and deliver C-terminal toxin domains to suppress target cell growth. Two classes of CdiA effectors that bind distinct cell surface receptors have been identified, but the molecular basis of receptor specificity is not understood. Alignment of BamA-specific CdiAEC93 from Escherichia coli EC93 and OmpC-specific CdiAEC536 from E. coli 536 suggests that the receptor-binding domain resides within a central region that varies between the two effectors. In support of this hypothesis, we find that CdiAEC93 fragments containing residues Arg1358 to Phe1646 bind specifically to purified BamA. Moreover, chimeric CdiAEC93 that carries the corresponding sequence from CdiAEC536 is endowed with OmpC-binding activity, demonstrating that this region dictates receptor specificity. A survey of E. coli CdiA proteins reveals two additional effector classes, which presumably recognize distinct receptors. Using a genetic approach, we identify the outer membrane nucleoside transporter Tsx as the receptor for a third class of CdiA effectors. Thus, CDI systems exploit multiple outer membrane proteins to identify and engage target cells. These results underscore the modularity of CdiA proteins and suggest that novel effectors can be constructed through genetic recombination to interchange different receptor-binding domains and toxic payloads.IMPORTANCE CdiB/CdiA two-partner secretion proteins mediate interbacterial competition through the delivery of polymorphic toxin domains. This process, known as contact-dependent growth inhibition (CDI), requires stable interactions between the CdiA effector protein and specific receptors on the surface of target bacteria. Here, we localize the receptor-binding domain to the central region of E. coli CdiA. Receptor-binding domains vary between CdiA proteins, and E. coli strains collectively encode at least four distinct effector classes. Further, we show that receptor specificity can be altered by exchanging receptor-binding regions, demonstrating the modularity of this domain. We propose that novel CdiA effectors are naturally generated through genetic recombination to interchange different receptor-binding domains and toxin payloads.
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24
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Pérez-Ortega J, Rodríguez A, Ribes E, Tommassen J, Arenas J. Interstrain Cooperation in Meningococcal Biofilms: Role of Autotransporters NalP and AutA. Front Microbiol 2017; 8:434. [PMID: 28382026 PMCID: PMC5360712 DOI: 10.3389/fmicb.2017.00434] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2016] [Accepted: 03/02/2017] [Indexed: 12/18/2022] Open
Abstract
Neisseria meningitidis (Nm) and Neisseria lactamica (Nl) are commensal bacteria that live in the human nasopharynx, where they form microcolonies. In contrast to Nl, Nm occasionally causes blood and/or meningitis infection with often fatal consequences. Here, we studied interactions between neisserial strains during biofilm formation. Fluorescent strains were engineered and analyzed for growth in single- and dual-strain biofilms with confocal laser-scanning microscopy. Different strains of diverse Neisseria species formed microcolonies of different sizes and morphologies. Pair-wise combinations of two invasive Nm strains and one Nm carrier isolate showed that these strains can coexist in spite of the fact that they produce toxins to combat congeners. This lack of competition was even observed when the biofilms were formed under nutrient limitation and can be explained by the observation that the separate microcolonies within mixed biofilms are mostly lineage specific. However, these microcolonies showed different levels of interaction. The coexistence of two strains was also observed in mixed biofilms of Nm and Nl strains. Inactivation of the autotransporter NalP, which prevents the release of the heparin-binding antigen NHBA and the α-peptide of IgA protease from the cell surface, and/or the production of autotransporter AutA increased interactions between microcolonies, as evidenced by close contacts between microcolonies on the substratum. Qualitative and quantitative analysis revealed an altered spatial distribution of each strain in mixed biofilms with consequences for the biomass, biofilm architecture and bacterial viability depending on the synthesis of NalP and AutA, the expression of which is prone to phase variation. Being in a consortium resulted in some cases in commensalism and cooperative behavior, which promoted attachment to the substratum or increased survival, possibly as result of the shared use of the biofilm matrix. We hypothesize that Nm strains can cooperate during host colonization, but, possibly, the different capacities of the microcolonies of each strain to resist the host's defenses limits the long-term coexistence of strains in the host.
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Affiliation(s)
- Jesús Pérez-Ortega
- Section Molecular Microbiology, Department of Biology, Utrecht University Utrecht, Netherlands
| | - Antonio Rodríguez
- Section Molecular Microbiology, Department of Biology, Utrecht University Utrecht, Netherlands
| | - Eduardo Ribes
- Section Molecular Microbiology, Department of Biology, Utrecht University Utrecht, Netherlands
| | - Jan Tommassen
- Section Molecular Microbiology, Department of Biology, Utrecht University Utrecht, Netherlands
| | - Jesús Arenas
- Section Molecular Microbiology, Department of Biology, Utrecht University Utrecht, Netherlands
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Arenas J, Tommassen J. Meningococcal Biofilm Formation: Let's Stick Together. Trends Microbiol 2017; 25:113-124. [DOI: 10.1016/j.tim.2016.09.005] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2016] [Revised: 09/13/2016] [Accepted: 09/16/2016] [Indexed: 11/26/2022]
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Arenas J, Paganelli FL, Rodríguez-Castaño P, Cano-Crespo S, van der Ende A, van Putten JPM, Tommassen J. Expression of the Gene for Autotransporter AutB of Neisseria meningitidis Affects Biofilm Formation and Epithelial Transmigration. Front Cell Infect Microbiol 2016; 6:162. [PMID: 27921012 PMCID: PMC5118866 DOI: 10.3389/fcimb.2016.00162] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2016] [Accepted: 11/07/2016] [Indexed: 11/15/2022] Open
Abstract
Neisseria meningitidis is a Gram-negative bacterium that resides as a commensal in the upper respiratory tract of humans, but occasionally, it invades the host and causes sepsis and/or meningitis. The bacterium can produce eight autotransporters, seven of which have been studied to some detail. The remaining one, AutB, has not been characterized yet. Here, we show that the autB gene is broadly distributed among pathogenic Neisseria spp. The gene is intact in most meningococcal strains. However, its expression is prone to phase variation due to slipped-strand mispairing at AAGC repeats located within the DNA encoding the signal sequence and is switched off in the vast majority of these strains. Moreover, various genetic disruptions prevent autB expression in most of the strains in which the gene is in phase indicating a strong selection against AutB synthesis. We observed that autB is expressed in two of the strains examined and that AutB is secreted and exposed at the cell surface. Functionality assays revealed that AutB synthesis promotes biofilm formation and delays the passage of epithelial cell layers in vitro. We hypothesize that this autotransporter is produced during the colonization process only in specific niches to facilitate microcolony formation, but its synthesis is switched off probably to evade the immune system and facilitate human tissue invasion.
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Affiliation(s)
- Jesús Arenas
- Department of Molecular Microbiology and Institute of Biomembranes, Utrecht University Utrecht, Netherlands
| | - Fernanda L Paganelli
- Department of Medical Microbiology, University Medical Center Utrecht Utrecht, Netherlands
| | - Patricia Rodríguez-Castaño
- Department of Molecular Microbiology and Institute of Biomembranes, Utrecht University Utrecht, Netherlands
| | - Sara Cano-Crespo
- Department of Molecular Microbiology and Institute of Biomembranes, Utrecht University Utrecht, Netherlands
| | - Arie van der Ende
- Department of Medical Microbiology, Academic Medical Center Amsterdam, Netherlands
| | - Jos P M van Putten
- Department of Infectious Diseases and Immunology, Faculty of Veterinary Medicine, Utrecht University Utrecht, Netherlands
| | - Jan Tommassen
- Department of Molecular Microbiology and Institute of Biomembranes, Utrecht University Utrecht, Netherlands
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CdiA Effectors from Uropathogenic Escherichia coli Use Heterotrimeric Osmoporins as Receptors to Recognize Target Bacteria. PLoS Pathog 2016; 12:e1005925. [PMID: 27723824 PMCID: PMC5056734 DOI: 10.1371/journal.ppat.1005925] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2016] [Accepted: 09/10/2016] [Indexed: 12/28/2022] Open
Abstract
Many Gram-negative bacterial pathogens express contact-dependent growth inhibition (CDI) systems that promote cell-cell interaction. CDI+ bacteria express surface CdiA effector proteins, which transfer their C-terminal toxin domains into susceptible target cells upon binding to specific receptors. CDI+ cells also produce immunity proteins that neutralize the toxin domains delivered from neighboring siblings. Here, we show that CdiAEC536 from uropathogenic Escherichia coli 536 (EC536) uses OmpC and OmpF as receptors to recognize target bacteria. E. coli mutants lacking either ompF or ompC are resistant to CDIEC536-mediated growth inhibition, and both porins are required for target-cell adhesion to inhibitors that express CdiAEC536. Experiments with single-chain OmpF fusions indicate that the CdiAEC536 receptor is heterotrimeric OmpC-OmpF. Because the OmpC and OmpF porins are under selective pressure from bacteriophages and host immune systems, their surface-exposed loops vary between E. coli isolates. OmpC polymorphism has a significant impact on CDIEC536 mediated competition, with many E. coli isolates expressing alleles that are not recognized by CdiAEC536. Analyses of recombinant OmpC chimeras suggest that extracellular loops L4 and L5 are important recognition epitopes for CdiAEC536. Loops L4 and L5 also account for much of the sequence variability between E. coli OmpC proteins, raising the possibility that CDI contributes to the selective pressure driving OmpC diversification. We find that the most efficient CdiAEC536 receptors are encoded by isolates that carry the same cdi gene cluster as E. coli 536. Thus, it appears that CdiA effectors often bind preferentially to "self" receptors, thereby promoting interactions between sibling cells. As a consequence, these effector proteins cannot recognize nor suppress the growth of many potential competitors. These findings suggest that self-recognition and kin selection are important functions of CDI. Bacterial pathogens often live in crowded communities where cells reside in close contact with one another. Many of these bacteria possess contact-dependent growth inhibition (CDI) systems, which allow cells to touch and inhibit each other using toxic CdiA proteins. CDI+ bacteria also produce immunity proteins that specifically protect the cell from the CdiA toxins of neighboring sibling cells. The CDI system from Escherichia coli EC93 was the first to be characterized and its CdiA toxin recognizes a receptor (BamA) that is identical in virtually all E. coli isolates. Here, we describe a different CDI system from uropathogenic E. coli 536, which causes urinary tract infections. In contrast to E. coli EC93, CdiA from E. coli 536 binds to receptor proteins (OmpC/OmpF) that vary widely between different E. coli isolates. Thus, uropathogenic E. coli preferentially bind and deliver toxins into sibling cells and other closely related E. coli strains. These results suggest that CDI systems distinguish between "self" and "non-self" cells. Moreover, because sibling cells are immune to CdiA-mediated growth inhibition, these findings raise the possibility that toxin exchange may be used for communication and cooperative behavior between genetically identical bacteria.
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Meningococcal Two-Partner Secretion Systems and Their Association with Outcome in Patients with Meningitis. Infect Immun 2016; 84:2534-40. [PMID: 27324486 PMCID: PMC4995907 DOI: 10.1128/iai.00160-16] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2016] [Accepted: 06/15/2016] [Indexed: 11/20/2022] Open
Abstract
Two-partner secretion (TPS) systems export large TpsA proteins to the surface and extracellular milieu. In meningococci, three different TPS systems exist, and of these, TPS system 2 (TPS2) and TPS3 can be detected by the host's immune system. We evaluated the distribution of TPS systems among clinical isolates from two prospective cohort studies comprising 373 patients with meningococcal meningitis. TPS system 1 was present in 91% of isolates, and system 2 and/or 3 was present in 67%. The TPS system distribution was related to clonal complexes. Infection with strains with TPS2 and/or TPS3 resulted in less severe disease and better outcomes than infection with strains without these systems. Using whole-blood stimulation experiments, we found no differences in the host cytokine response between patients infected with TPS system 2 and 3 knockout strains and patients infected with a wild-type strain. In conclusion, meningococcal TPS system 2 and/or 3 is associated with disease severity and outcome in patients with meningitis.
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Arenas J, de Maat V, Catón L, Krekorian M, Herrero JC, Ferrara F, Tommassen J. Fratricide activity of MafB protein of N. meningitidis strain B16B6. BMC Microbiol 2015; 15:156. [PMID: 26242409 PMCID: PMC4524018 DOI: 10.1186/s12866-015-0493-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2015] [Accepted: 07/24/2015] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Neisseria meningitidis is an inhabitant of the mucosal surfaces of the human nasopharynx. We recently demonstrated that the secreted meningococcal Two-partner secretion protein A (TpsA) is involved in interbacterial competition. The C-terminal end of the large TpsA protein contains a small toxic domain that inhibits the growth of target bacteria. The producing cells are protected from this toxic activity by a small immunity protein that is encoded by the gene immediately downstream of the tpsA gene. Further downstream on the chromosome, a repertoire of toxic modules, designated tpsC cassettes, is encoded that could replace the toxic module of TpsA by recombination. Each tpsC cassette is associated with a gene encoding a cognate immunity protein. RESULTS Blast searchers using the toxic domains of TpsA and TpsC proteins as queries identified homologies with the C-terminal part of neisserial MafB proteins, which, for the rest, showed no sequence similarity to TpsA proteins. On the chromosome, mafB genes are part of genomic islands, which include cassettes for additional toxic modules as well as genes putatively encoding immunity proteins. We demonstrate that a MafB protein of strain B16B6 inhibits the growth of a strain that does not produce the corresponding immunity protein. Assays in E. coli confirmed that the C-terminal region of MafB is responsible for toxicity, which is inhibited by the cognate immunity protein. Pull-down assays revealed direct interaction between MafB toxic domains and the cognate immunity proteins. CONCLUSIONS The meningococcal MafB proteins are novel toxic proteins involved in interbacterial competition.
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Affiliation(s)
- Jesús Arenas
- Department of Molecular Microbiology, Utrecht University, Padualaan 8, 3584, CH, Utrecht, The Netherlands.
| | - Vincent de Maat
- Department of Molecular Microbiology, Utrecht University, Padualaan 8, 3584, CH, Utrecht, The Netherlands.
| | - Laura Catón
- Department of Molecular Microbiology, Utrecht University, Padualaan 8, 3584, CH, Utrecht, The Netherlands.
| | - Massis Krekorian
- Department of Molecular Microbiology, Utrecht University, Padualaan 8, 3584, CH, Utrecht, The Netherlands.
| | - Juan Cruz Herrero
- Department of Molecular Microbiology, Utrecht University, Padualaan 8, 3584, CH, Utrecht, The Netherlands.
| | - Flavio Ferrara
- Department of Molecular Microbiology, Utrecht University, Padualaan 8, 3584, CH, Utrecht, The Netherlands.
| | - Jan Tommassen
- Department of Molecular Microbiology, Utrecht University, Padualaan 8, 3584, CH, Utrecht, The Netherlands.
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Ruhe ZC, Townsley L, Wallace AB, King A, Van der Woude MW, Low DA, Yildiz FH, Hayes CS. CdiA promotes receptor-independent intercellular adhesion. Mol Microbiol 2015; 98:175-92. [PMID: 26135212 DOI: 10.1111/mmi.13114] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/30/2015] [Indexed: 01/02/2023]
Abstract
CdiB/CdiA proteins mediate inter-bacterial competition in a process termed contact-dependent growth inhibition (CDI). Filamentous CdiA exoproteins extend from CDI(+) cells and bind specific receptors to deliver toxins into susceptible target bacteria. CDI has also been implicated in auto-aggregation and biofilm formation in several species, but the contribution of CdiA-receptor interactions to these multi-cellular behaviors has not been examined. Using Escherichia coli isolate EC93 as a model, we show that cdiA and bamA receptor mutants are defective in biofilm formation, suggesting a prominent role for CdiA-BamA mediated cell-cell adhesion. However, CdiA also promotes auto-aggregation in a BamA-independent manner, indicating that the exoprotein possesses an additional adhesin activity. Cells must express CdiA in order to participate in BamA-independent aggregates, suggesting that adhesion could be mediated by homotypic CdiA-CdiA interactions. The BamA-dependent and BamA-independent interaction domains map to distinct regions within the CdiA filament. Thus, CdiA orchestrates a collective behavior that is independent of its growth-inhibition activity. This adhesion should enable 'greenbeard' discrimination, in which genetically unrelated individuals cooperate with one another based on a single shared trait. This kind-selective social behavior could provide immediate fitness benefits to bacteria that acquire the systems through horizontal gene transfer.
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Affiliation(s)
- Zachary C Ruhe
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, CA, 93106-9625, USA
| | - Loni Townsley
- Department of Microbiology and Environmental Toxicology, University of California, Santa Cruz, CA, 95064, USA
| | - Adam B Wallace
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, CA, 93106-9625, USA
| | - Andrew King
- Centre for Immunology and Infection, Hull York Medical School and the Department of Biology, University of York, York, YO10 5DD, UK
| | - Marjan W Van der Woude
- Centre for Immunology and Infection, Hull York Medical School and the Department of Biology, University of York, York, YO10 5DD, UK
| | - David A Low
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, CA, 93106-9625, USA.,Biomolecular Science and Engineering Program, University of California, Santa Barbara, CA, 93106-9625, USA
| | - Fitnat H Yildiz
- Department of Microbiology and Environmental Toxicology, University of California, Santa Cruz, CA, 95064, USA
| | - Christopher S Hayes
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, CA, 93106-9625, USA.,Biomolecular Science and Engineering Program, University of California, Santa Barbara, CA, 93106-9625, USA
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Tan K, Johnson PM, Stols L, Boubion B, Eschenfeldt W, Babnigg G, Hayes CS, Joachimiak A, Goulding CW. The structure of a contact-dependent growth-inhibition (CDI) immunity protein from Neisseria meningitidis MC58. Acta Crystallogr F Struct Biol Commun 2015; 71:702-9. [PMID: 26057799 PMCID: PMC4461334 DOI: 10.1107/s2053230x15006585] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2015] [Accepted: 03/31/2015] [Indexed: 01/01/2023] Open
Abstract
Contact-dependent growth inhibition (CDI) is an important mechanism of intercellular competition between neighboring Gram-negative bacteria. CDI systems encode large surface-exposed CdiA effector proteins that carry a variety of C-terminal toxin domains (CdiA-CTs). All CDI(+) bacteria also produce CdiI immunity proteins that specifically bind to the cognate CdiA-CT and neutralize its toxin activity to prevent auto-inhibition. Here, the X-ray crystal structure of a CdiI immunity protein from Neisseria meningitidis MC58 is presented at 1.45 Å resolution. The CdiI protein has structural homology to the Whirly family of RNA-binding proteins, but appears to lack the characteristic nucleic acid-binding motif of this family. Sequence homology suggests that the cognate CdiA-CT is related to the eukaryotic EndoU family of RNA-processing enzymes. A homology model is presented of the CdiA-CT based on the structure of the XendoU nuclease from Xenopus laevis. Molecular-docking simulations predict that the CdiA-CT toxin active site is occluded upon binding to the CdiI immunity protein. Together, these observations suggest that the immunity protein neutralizes toxin activity by preventing access to RNA substrates.
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Affiliation(s)
- Kemin Tan
- Midwest Center for Structural Genomics, Argonne National Laboratory, Argonne, IL 60439, USA
- Structural Biology Center, Biosciences, Argonne National Laboratory, Argonne, IL 60439, USA
| | - Parker M. Johnson
- Department of Molecular Biology and Biochemistry, University of California Irvine, Irvine, CA 92697, USA
| | - Lucy Stols
- Midwest Center for Structural Genomics, Argonne National Laboratory, Argonne, IL 60439, USA
| | - Bryan Boubion
- Department of Molecular Biology and Biochemistry, University of California Irvine, Irvine, CA 92697, USA
| | - William Eschenfeldt
- Midwest Center for Structural Genomics, Argonne National Laboratory, Argonne, IL 60439, USA
| | - Gyorgy Babnigg
- Midwest Center for Structural Genomics, Argonne National Laboratory, Argonne, IL 60439, USA
| | - Christopher S. Hayes
- Department of Molecular, Cellular and Developmental Biology, University of California Santa Barbara, Santa Barbara, CA 93106, USA
- Biomolecular Science and Engineering Program, University of California Santa Barbara, Santa Barbara, CA 93106, USA
| | - Andrezj Joachimiak
- Midwest Center for Structural Genomics, Argonne National Laboratory, Argonne, IL 60439, USA
- Structural Biology Center, Biosciences, Argonne National Laboratory, Argonne, IL 60439, USA
| | - Celia W. Goulding
- Department of Molecular Biology and Biochemistry, University of California Irvine, Irvine, CA 92697, USA
- Department of Pharmaceutical Sciences, University of California Irvine, Irvine, CA 92697, USA
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Abstract
Bacteria have evolved numerous strategies to increase their competitiveness and fight against each other. Indeed, a large arsenal of antibacterial weapons is available in order to inhibit the proliferation of competitor cells. Polymorphic toxin systems (PTS), recently identified by bioinformatics in all major bacterial lineages, correspond to such a system primarily involved in conflict between related bacterial strains. They are typically composed of a secreted multidomain toxin, a protective immunity protein, and multiple cassettes encoding alternative toxic domains. The C-terminal domains of polymorphic toxins carry the toxic activity, whereas the N-terminal domains are related to the trafficking mode. In silico analysis of PTS identified over 150 distinct toxin domains, including putative nuclease, deaminase, or peptidase domains. Immunity genes found immediately downstream of the toxin genes encode small proteins that protect bacteria against their own toxins or against toxins secreted by neighboring cells. PTS encompass well-known colicins and pyocins, contact-dependent growth inhibition systems which include CdiA and Rhs toxins and some effectors of type VI secretion systems. We have recently characterized the MafB toxins, a new family of PTS deployed by pathogenic Neisseria spp. Many other putative PTS have been identified by in silico predictions but have yet to be characterized experimentally. However, the high number of these systems suggests that PTS have a fundamental role in bacterial biology that is likely to extend beyond interbacterial competition.
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Koskiniemi S, Garza-Sánchez F, Edman N, Chaudhuri S, Poole SJ, Manoil C, Hayes CS, Low DA. Genetic analysis of the CDI pathway from Burkholderia pseudomallei 1026b. PLoS One 2015; 10:e0120265. [PMID: 25786241 PMCID: PMC4364669 DOI: 10.1371/journal.pone.0120265] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2014] [Accepted: 01/21/2015] [Indexed: 12/03/2022] Open
Abstract
Contact-dependent growth inhibition (CDI) is a mode of inter-bacterial competition mediated by the CdiB/CdiA family of two-partner secretion systems. CdiA binds to receptors on susceptible target bacteria, then delivers a toxin domain derived from its C-terminus. Studies with Escherichia coli suggest the existence of multiple CDI growth-inhibition pathways, whereby different systems exploit distinct target-cell proteins to deliver and activate toxins. Here, we explore the CDI pathway in Burkholderia using the CDIIIBp1026b system encoded on chromosome II of Burkholderia pseudomallei 1026b as a model. We took a genetic approach and selected Burkholderia thailandensis E264 mutants that are resistant to growth inhibition by CDIIIBp1026b. We identified mutations in three genes, BTH_I0359, BTH_II0599, and BTH_I0986, each of which confers resistance to CDIIIBp1026b. BTH_I0359 encodes a small peptide of unknown function, whereas BTH_II0599 encodes a predicted inner membrane transport protein of the major facilitator superfamily. The inner membrane localization of BTH_II0599 suggests that it may facilitate translocation of CdiA-CTIIBp1026b toxin from the periplasm into the cytoplasm of target cells. BTH_I0986 encodes a putative transglycosylase involved in lipopolysaccharide (LPS) synthesis. ∆BTH_I0986 mutants have altered LPS structure and do not interact with CDI+ inhibitor cells to the same extent as BTH_I0986+ cells, suggesting that LPS could function as a receptor for CdiAIIBp1026b. Although ∆BTH_I0359, ∆BTH_II0599, and ∆BTH_I0986 mutations confer resistance to CDIIIBp1026b, they provide no protection against the CDIE264 system deployed by B. thailandensis E264. Together, these findings demonstrate that CDI growth-inhibition pathways are distinct and can differ significantly even between closely related species.
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Affiliation(s)
- Sanna Koskiniemi
- Department of Molecular, Cellular and Developmental Biology, University of California Santa Barbara, Santa Barbara, California, United States of America
| | - Fernando Garza-Sánchez
- Department of Molecular, Cellular and Developmental Biology, University of California Santa Barbara, Santa Barbara, California, United States of America
| | - Natasha Edman
- Department of Molecular, Cellular and Developmental Biology, University of California Santa Barbara, Santa Barbara, California, United States of America
| | - Swarnava Chaudhuri
- Department of Molecular, Cellular and Developmental Biology, University of California Santa Barbara, Santa Barbara, California, United States of America
| | - Stephen J. Poole
- Department of Molecular, Cellular and Developmental Biology, University of California Santa Barbara, Santa Barbara, California, United States of America
| | - Colin Manoil
- Department of Genome Sciences, Box 355065, University of Washington, Seattle, Washington, United States of America
| | - Christopher S. Hayes
- Department of Molecular, Cellular and Developmental Biology, University of California Santa Barbara, Santa Barbara, California, United States of America
- Biomolecular Science and Engineering Program, University of California Santa Barbara, Santa Barbara, California, United States of America
| | - David A. Low
- Department of Molecular, Cellular and Developmental Biology, University of California Santa Barbara, Santa Barbara, California, United States of America
- Biomolecular Science and Engineering Program, University of California Santa Barbara, Santa Barbara, California, United States of America
- * E-mail:
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A new family of secreted toxins in pathogenic Neisseria species. PLoS Pathog 2015; 11:e1004592. [PMID: 25569427 PMCID: PMC4287609 DOI: 10.1371/journal.ppat.1004592] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2014] [Accepted: 11/26/2014] [Indexed: 11/23/2022] Open
Abstract
The genus Neisseria includes both commensal and pathogenic species which are genetically closely related. However, only meningococcus and gonococcus are important human pathogens. Very few toxins are known to be secreted by pathogenic Neisseria species. Recently, toxins secreted via type V secretion system and belonging to the widespread family of contact-dependent inhibition (CDI) toxins have been described in numerous species including meningococcus. In this study, we analyzed loci containing the maf genes in N. meningitidis and N. gonorrhoeae and proposed a novel uniform nomenclature for maf genomic islands (MGIs). We demonstrated that mafB genes encode secreted polymorphic toxins and that genes immediately downstream of mafB encode a specific immunity protein (MafI). We focused on a MafB toxin found in meningococcal strain NEM8013 and characterized its EndoU ribonuclease activity. maf genes represent 2% of the genome of pathogenic Neisseria, and are virtually absent from non-pathogenic species, thus arguing for an important biological role. Indeed, we showed that overexpression of one of the four MafB toxins of strain NEM8013 provides an advantage in competition assays, suggesting a role of maf loci in niche adaptation. Many bacteria are able to secrete toxins targeted against neighboring cells. In order to protect themselves against their own toxin, they also express an “immunity” protein. In silico analysis of bacterial genomes predicts that numerous genes could encode potential new toxin-immunity systems. The recently described CDI system is involved in contact-dependent inhibition of growth and confers to its host strain a significant advantage in competitive ecosystems such as the gastro-intestinal tract. Indeed, an Escherichia coli CDI+ strain is able to outcompete CDI- strains and to become predominant. Here, we show that a large family of genes called “maf”, found in pathogenic Neisseria species, encodes a toxin-immunity system. We demonstrate that a toxin named MafBMGI-1NEM8013 inhibits the growth of E. coli by degrading RNA and show that the immunity protein MafIMGI-1NEM8013 is able to abolish the toxicity. MafB toxins exhibit highly variable toxic domains. This variability of secreted toxins could be important to compete against bacteria of different species sharing the same reservoir. Since a strain may contain numerous toxin-immunity systems that can all play a role in interbacterial competition, deciphering interactions between these systems will allow a better understanding of complex bacterial communities.
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Ruhe ZC, Nguyen JY, Beck CM, Low DA, Hayes CS. The proton-motive force is required for translocation of CDI toxins across the inner membrane of target bacteria. Mol Microbiol 2014; 94:466-81. [PMID: 25174572 DOI: 10.1111/mmi.12779] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/28/2014] [Indexed: 01/09/2023]
Abstract
Contact-dependent growth inhibition (CDI) is a mode of bacterial competition orchestrated by the CdiB/CdiA family of two-partner secretion proteins. The CdiA effector extends from the surface of CDI(+) inhibitor cells, binds to receptors on neighbouring bacteria and delivers a toxin domain derived from its C-terminal region (CdiA-CT). Here, we show that CdiA-CT toxin translocation requires the proton-motive force (pmf) within target bacteria. The pmf is also critical for the translocation of colicin toxins, which exploit the energized Ton and Tol systems to cross the outer membrane. However, CdiA-CT translocation is clearly distinct from known colicin-import pathways because ΔtolA ΔtonB target cells are fully sensitive to CDI. Moreover, we provide evidence that CdiA-CT toxins can be transferred into the periplasm of de-energized target bacteria, indicating that transport across the outer membrane is independent of the pmf. Remarkably, CDI toxins transferred under de-energized conditions remain competent to enter the target-cell cytoplasm once the pmf is restored. Collectively, these results indicate that outer- and inner-membrane translocation steps can be uncoupled, and that the pmf is required for CDI toxin transport from the periplasm to the target-cell cytoplasm.
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Affiliation(s)
- Zachary C Ruhe
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA, 93106-9625, USA
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ur Rahman S, Arenas J, Öztürk H, Dekker N, van Ulsen P. The polypeptide transport-associated (POTRA) domains of TpsB transporters determine the system specificity of two-partner secretion systems. J Biol Chem 2014; 289:19799-809. [PMID: 24872418 DOI: 10.1074/jbc.m113.544627] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The two-partner secretion (TPS) systems of Gram-negative bacteria secrete large TpsA exoproteins by a dedicated TpsB transporter in the outer membrane. TpsBs contain an N-terminal module located in the periplasm that includes two polypeptide transport-associated (POTRA) domains. These are thought to initiate secretion of a TpsA by binding its N-terminal secretion signal, called the TPS domain. Neisseria meningitidis encodes up to five TpsA proteins that are secreted via only two TpsB transporters: TpsB1 and TpsB2. Of these two, the TpsB2 recognizes the TPS domains of all TpsAs, despite their sequence diversity. By contrast, the TpsB1 shows a limited recognition of a TPS domain that is shared by two TpsAs. The difference in substrate specificity of the TpsBs enabled us to investigate the role of the POTRA domains in the selection of TPS domains. We tested secretion of TPS domains or full-length TpsAs by TpsB mutants with deleted, duplicated, and exchanged POTRA domains. Exchanging the two POTRA domains of a TpsB resulted in a switch in specificity. Furthermore, exchanging a single POTRA domain showed that each of the two domains contributed to the cargo selection. Remarkably, the order of the POTRA domains could be reversed without affecting substrate selection, but this aberrant order did result in an alternatively processed secretion product. Our results suggest that secretion of a TpsA is initiated by engaging both POTRA domains of a TpsB transporter and that these select the cognate TpsAs for secretion.
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Affiliation(s)
- Sadeeq ur Rahman
- From the Section of Molecular Microbiology, Department of Molecular Cell Biology, VU University, de Boelelaan 1085, 1081 HV Amsterdam, The Netherlands and
| | - Jesús Arenas
- the Section of Molecular Microbiology, Department of Biology, Utrecht University, 3584 CH Utrecht, The Netherlands
| | - Hülya Öztürk
- From the Section of Molecular Microbiology, Department of Molecular Cell Biology, VU University, de Boelelaan 1085, 1081 HV Amsterdam, The Netherlands and
| | - Nicole Dekker
- From the Section of Molecular Microbiology, Department of Molecular Cell Biology, VU University, de Boelelaan 1085, 1081 HV Amsterdam, The Netherlands and
| | - Peter van Ulsen
- From the Section of Molecular Microbiology, Department of Molecular Cell Biology, VU University, de Boelelaan 1085, 1081 HV Amsterdam, The Netherlands and
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