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Zuke JD, Erickson R, Hummels KR, Burton BM. Visualizing dynamic competence pili and DNA capture throughout the long axis of Bacillus subtilis. J Bacteriol 2023; 205:e0015623. [PMID: 37695859 PMCID: PMC10521363 DOI: 10.1128/jb.00156-23] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2023] [Accepted: 06/05/2023] [Indexed: 09/13/2023] Open
Abstract
The first step in the process of bacterial natural transformation is DNA capture. Although long hypothesized based on genetics and functional experiments, the pilus structure responsible for initial DNA binding had not yet been visualized for Bacillus subtilis. Here, we visualize functional competence pili in Bacillus subtilis using fluorophore-conjugated maleimide labeling in conjunction with epifluorescence microscopy. In strains that produce pilin monomers within tenfold of wild-type levels, the median length of detectable pili is 300 nm. These pili are retractile and associate with DNA. The analysis of pilus distribution at the cell surface reveals that they are predominantly located along the long axis of the cell. The distribution is consistent with localization of proteins associated with subsequent transformation steps, DNA binding, and DNA translocation in the cytosol. These data suggest a distributed model for B. subtilis transformation machinery, in which initial steps of DNA capture occur throughout the long axis of the cell and subsequent steps may also occur away from the cell poles. IMPORTANCE This work provides novel visual evidence for DNA translocation across the cell wall during Bacillus subtilis natural competence, an essential step in the natural transformation process. Our data demonstrate the existence of natural competence-associated retractile pili that can bind exogenous DNA. Furthermore, we show that pilus biogenesis occurs throughout the cell long axis. These data strongly support DNA translocation occurring all along the lateral cell wall during natural competence, wherein pili are produced, bind to free DNA in the extracellular space, and finally retract to pull the bound DNA through the gap in the cell wall created during pilus biogenesis.
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Affiliation(s)
- Jason D. Zuke
- Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Microbiology Doctoral Training Program, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Rachel Erickson
- Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Katherine R. Hummels
- Department of Microbiology and Immunology, Harvard Medical School, Boston, MA, USA
| | - Briana M. Burton
- Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin, USA
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Zuke JD, Erickson R, Hummels KR, Burton BM. Visualizing dynamic competence pili and DNA capture throughout the long axis of Bacillus subtilis. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.05.26.542325. [PMID: 37292776 PMCID: PMC10246001 DOI: 10.1101/2023.05.26.542325] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The first step in the process of bacterial natural transformation is DNA capture. Although long-hypothesized based on genetics and functional experiments, the pilus structure responsible for initial DNA-binding had not yet been visualized for Bacillus subtilis. Here, we visualize functional competence pili in Bacillus subtilis using fluorophore-conjugated maleimide labeling in conjunction with epifluorescence microscopy. In strains that produce pilin monomers within ten-fold of wild type levels, the median length of detectable pili is 300nm. These pili are retractile and associate with DNA. Analysis of pilus distribution at the cell surface reveals that they are predominantly located along the long axis of the cell. The distribution is consistent with localization of proteins associated with subsequent transformation steps, DNA-binding and DNA translocation in the cytosol. These data suggest a distributed model for B. subtilis transformation machinery, in which initial steps of DNA capture occur throughout the long axis of the cell and subsequent steps may also occur away from the cell poles.
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Affiliation(s)
- Jason D. Zuke
- Department of Bacteriology, University of Wisconsin - Madison
- Microbiology Doctoral Training Program, University of Wisconsin - Madison
| | - Rachel Erickson
- Department of Bacteriology, University of Wisconsin - Madison
| | - Katherine R. Hummels
- Current address: Department of Microbiology and Immunology, Harvard Medical School
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Palladino G, Caroselli E, Tavella T, D'Amico F, Prada F, Mancuso A, Franzellitti S, Rampelli S, Candela M, Goffredo S, Biagi E. Metagenomic shifts in mucus, tissue and skeleton of the coral Balanophyllia europaea living along a natural CO 2 gradient. ISME COMMUNICATIONS 2022; 2:65. [PMID: 37938252 PMCID: PMC9723718 DOI: 10.1038/s43705-022-00152-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/22/2022] [Revised: 07/01/2022] [Accepted: 07/12/2022] [Indexed: 05/13/2023]
Abstract
Using the Mediterranean coral Balanophyllia europaea naturally growing along a pH gradient close to Panarea island (Italy) as a model, we explored the role of host-associated microbiomes in coral acclimatization to ocean acidification (OA). Coral samples were collected at three sites along the gradient, mimicking seawater conditions projected for 2100 under different IPCC (The Intergovernmental Panel on Climate Change) scenarios, and mucus, soft tissue and skeleton associated microbiomes were characterized by shotgun metagenomics. According to our findings, OA induced functional changes in the microbiomes genetic potential that could mitigate the sub-optimal environmental conditions at three levels: i. selection of bacteria genetically equipped with functions related to stress resistance; ii. shifts in microbial carbohydrate metabolism from energy production to maintenance of cell membranes and walls integrity; iii. gain of functions able to respond to variations in nitrogen needs at the holobiont level, such as genes devoted to organic nitrogen mobilization. We hence provided hypotheses about the functional role of the coral associated microbiome in favoring host acclimatation to OA, remarking on the importance of considering the crosstalk among all the components of the holobiont to unveil how and to what extent corals will maintain their functionality under forthcoming ocean conditions.
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Affiliation(s)
- Giorgia Palladino
- Unit of Microbiome Science and Biotechnology, Department of Pharmacy and Biotechnology, University of Bologna, via Belmeloro 6, 40126, Bologna, Italy
- Fano Marine Center, The Inter-Institute Center for Research on Marine Biodiversity, Resources and Biotechnologies, viale Adriatico 1/N, 61032, Fano, Pesaro Urbino, Italy
| | - Erik Caroselli
- Fano Marine Center, The Inter-Institute Center for Research on Marine Biodiversity, Resources and Biotechnologies, viale Adriatico 1/N, 61032, Fano, Pesaro Urbino, Italy
- Marine Science Group, Department of Biological, Geological and Environmental Sciences, University of Bologna, via Selmi 3, 40126, Bologna, Italy
| | - Teresa Tavella
- Unit of Microbiome Science and Biotechnology, Department of Pharmacy and Biotechnology, University of Bologna, via Belmeloro 6, 40126, Bologna, Italy
| | - Federica D'Amico
- Unit of Microbiome Science and Biotechnology, Department of Pharmacy and Biotechnology, University of Bologna, via Belmeloro 6, 40126, Bologna, Italy
| | - Fiorella Prada
- Fano Marine Center, The Inter-Institute Center for Research on Marine Biodiversity, Resources and Biotechnologies, viale Adriatico 1/N, 61032, Fano, Pesaro Urbino, Italy
- Marine Science Group, Department of Biological, Geological and Environmental Sciences, University of Bologna, via Selmi 3, 40126, Bologna, Italy
| | - Arianna Mancuso
- Fano Marine Center, The Inter-Institute Center for Research on Marine Biodiversity, Resources and Biotechnologies, viale Adriatico 1/N, 61032, Fano, Pesaro Urbino, Italy
- Marine Science Group, Department of Biological, Geological and Environmental Sciences, University of Bologna, via Selmi 3, 40126, Bologna, Italy
| | - Silvia Franzellitti
- Fano Marine Center, The Inter-Institute Center for Research on Marine Biodiversity, Resources and Biotechnologies, viale Adriatico 1/N, 61032, Fano, Pesaro Urbino, Italy
- Animal and Environmental Physiology Laboratory, Department of Biological, Geological and Environmental Sciences, University of Bologna, via Sant'Alberto 163, 48123, Ravenna, Italy
| | - Simone Rampelli
- Unit of Microbiome Science and Biotechnology, Department of Pharmacy and Biotechnology, University of Bologna, via Belmeloro 6, 40126, Bologna, Italy
| | - Marco Candela
- Unit of Microbiome Science and Biotechnology, Department of Pharmacy and Biotechnology, University of Bologna, via Belmeloro 6, 40126, Bologna, Italy.
- Fano Marine Center, The Inter-Institute Center for Research on Marine Biodiversity, Resources and Biotechnologies, viale Adriatico 1/N, 61032, Fano, Pesaro Urbino, Italy.
| | - Stefano Goffredo
- Fano Marine Center, The Inter-Institute Center for Research on Marine Biodiversity, Resources and Biotechnologies, viale Adriatico 1/N, 61032, Fano, Pesaro Urbino, Italy.
- Marine Science Group, Department of Biological, Geological and Environmental Sciences, University of Bologna, via Selmi 3, 40126, Bologna, Italy.
| | - Elena Biagi
- Unit of Microbiome Science and Biotechnology, Department of Pharmacy and Biotechnology, University of Bologna, via Belmeloro 6, 40126, Bologna, Italy
- Fano Marine Center, The Inter-Institute Center for Research on Marine Biodiversity, Resources and Biotechnologies, viale Adriatico 1/N, 61032, Fano, Pesaro Urbino, Italy
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ComFC mediates transport and handling of single-stranded DNA during natural transformation. Nat Commun 2022; 13:1961. [PMID: 35414142 PMCID: PMC9005727 DOI: 10.1038/s41467-022-29494-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2021] [Accepted: 03/17/2022] [Indexed: 11/09/2022] Open
Abstract
The ComFC protein is essential for natural transformation, a process that plays a major role in the spread of antibiotic resistance genes and virulence factors across bacteria. However, its role remains largely unknown. Here, we show that Helicobacter pylori ComFC is involved in DNA transport through the cell membrane, and is required for the handling of the single-stranded DNA once it is delivered into the cytoplasm. The crystal structure of ComFC includes a zinc-finger motif and a putative phosphoribosyl transferase domain, both necessary for the protein's in vivo activity. Furthermore, we show that ComFC is a membrane-associated protein with affinity for single-stranded DNA. Our results suggest that ComFC provides the link between the transport of the transforming DNA into the cytoplasm and its handling by the recombination machinery.
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Natural transformation protein ComFA exhibits single-stranded DNA translocase activity. J Bacteriol 2022; 204:e0051821. [PMID: 35041498 DOI: 10.1128/jb.00518-21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Natural transformation is one of the major mechanisms of horizontal gene transfer in bacterial populations and has been demonstrated in numerous species of bacteria. Despite the prevalence of natural transformation, much of the molecular mechanism remains unexplored. One major outstanding question is how the cell powers DNA import, which is rapid and highly processive. ComFA is one of a handful of proteins required for natural transformation in gram-positive bacteria. Its structural resemblance to the DEAD-box helicase family has led to a long-held hypothesis that ComFA acts as a motor to help drive DNA import into the cytosol. Here, we explored the helicase and translocase activity of ComFA to address this hypothesis. We followed the DNA-dependent ATPase activity of ComFA and, combined with mathematical modeling, demonstrated that ComFA likely translocates on single-stranded DNA from 5' to 3'. However, this translocase activity does not lead to DNA unwinding in the conditions we tested. Further, we analyzed the ATPase cycle of ComFA and found that ATP hydrolysis stimulates the release of DNA, providing a potential mechanism for translocation. These findings help define the molecular contribution of ComFA to natural transformation and support the conclusion that ComFA plays a key role in powering DNA uptake. Importance Competence, or the ability of bacteria to take up and incorporate foreign DNA in a process called natural transformation, is common in the bacterial kingdom. Research in several bacterial species suggests that long, contiguous stretches of DNA are imported into cells in a processive manner, but how bacteria power transformation remains unclear. Our finding that ComFA, a DEAD-box helicase required for competence in gram-positive bacteria, translocates on single-stranded DNA from 5' to 3', supports the long held hypothesis that ComFA may be the motor powering DNA transport during natural transformation. Moreover, ComFA may be a previously unidentified type of DEAD-box helicase-one with the capability of extended translocation on single-stranded DNA.
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Single molecule dynamics of DNA receptor ComEA, membrane permease ComEC and taken up DNA in competent Bacillus subtilis cells. J Bacteriol 2021; 204:e0057221. [PMID: 34928178 DOI: 10.1128/jb.00572-21] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In competent Gram-negative and Gram-positive bacteria, double stranded DNA is taken up through the outer cell membrane and/or the cell wall, and is bound by ComEA, which in Bacillus subtilis is a membrane protein. DNA is converted to single stranded DNA, and transported through the cell membrane via ComEC. We show that in Bacillus subtilis, the C-terminus of ComEC, thought to act as a nuclease, is not only important for DNA uptake, as judged from a loss of transformability, but also for the localization of ComEC to the cell pole and its mobility within the cell membrane. Using single molecule tracking, we show that only 13% of ComEC molecules are statically localised at the pole, while 87% move throughout the cell membrane. These experiments suggest that recruitment of ComEC to the cell pole is mediated by a diffusion/capture mechanism. Mutation of a conserved aspartate residue in the C-terminus, likely affecting metal binding, strongly impairs transformation efficiency, suggesting that this periplasmic domain of ComEC could indeed serve a catalytic function as nuclease. By tracking fluorescently labeled DNA, we show that taken up DNA has a similar mobility as a protein, in spite of being a large polymer. DNA dynamics are similar within the periplasm as those of ComEA, suggesting that most taken up molecules are bound to ComEA. We show that DNA can be highly mobile within the periplasm, indicating that this subcellular space can act as reservoir for taken up DNA, before its entry into the cytosol. Importance Bacteria can take up DNA from the environment and incorporate it into their chromosome, termed "natural competence" that can result in the uptake of novel genetic information. We show that fluorescently labelled DNA moves within the periplasm of competent Bacillus subtilis cells, with similar dynamics as DNA receptor ComEA. This indicates that DNA can accumulate in the periplasm, likely bound by ComEA, and thus can be stored before uptake at the cell pole, via integral membrane DNA permease ComEC. Assembly of the latter assembles at the cell pole likely occurs by a diffusion-capture mechanism. DNA uptake into cells thus takes a detour through the entire periplasm, and involves a high degree of free diffusion along and within the cell membrane.
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Hahn J, DeSantis M, Dubnau D. Mechanisms of Transforming DNA Uptake to the Periplasm of Bacillus subtilis. mBio 2021; 12:e0106121. [PMID: 34126763 PMCID: PMC8262900 DOI: 10.1128/mbio.01061-21] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2021] [Accepted: 05/05/2021] [Indexed: 11/20/2022] Open
Abstract
We demonstrate here that the acquisition of DNase resistance by transforming DNA, often assumed to indicate transport to the cytoplasm, reflects uptake to the periplasm, requiring a reevaluation of conclusions about the roles of several proteins in transformation. The new evidence suggests that the transformation pilus is needed for DNA binding to the cell surface near the cell poles and for the initiation of uptake. The cellular distribution of the membrane-anchored ComEA of Bacillus subtilis does not dramatically change during DNA uptake as does the unanchored ComEA of Vibrio and Neisseria. Instead, our evidence suggests that ComEA stabilizes the attachment of transforming DNA at localized regions in the periplasm and then mediates uptake, probably by a Brownian ratchet mechanism. Following that, the DNA is transferred to periplasmic portions of the channel protein ComEC, which plays a previously unsuspected role in uptake to the periplasm. We show that the transformation endonuclease NucA also facilitates uptake to the periplasm and that the previously demonstrated role of ComFA in the acquisition of DNase resistance derives from the instability of ComGA when ComFA is deleted. These results prompt a new understanding of the early stages of DNA uptake for transformation. IMPORTANCE Transformation is a widely distributed mechanism of bacterial horizontal gene transfer that plays a role in the spread of antibiotic resistance and virulence genes and more generally in evolution. Although transformation was discovered nearly a century ago and most, if not all the proteins required have been identified in several bacterial species, much remains poorly understood about the molecular mechanism of DNA uptake. This study uses epifluorescence microscopy to investigate the passage of labeled DNA into the compartment between the cell wall and the cell membrane of Bacillus subtilis, a necessary early step in transformation. The roles of individual proteins in this process are identified, and their modes of action are clarified.
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Affiliation(s)
- Jeanette Hahn
- Public Health Research Institute, Rutgers University, Newark, New Jersey, USA
- Department of Microbiology, Biochemistry and Molecular Genetics, New Jersey Medical School, Rutgers University, Newark, New Jersey, USA
| | - Micaela DeSantis
- Public Health Research Institute, Rutgers University, Newark, New Jersey, USA
- Department of Microbiology, Biochemistry and Molecular Genetics, New Jersey Medical School, Rutgers University, Newark, New Jersey, USA
| | - David Dubnau
- Public Health Research Institute, Rutgers University, Newark, New Jersey, USA
- Department of Microbiology, Biochemistry and Molecular Genetics, New Jersey Medical School, Rutgers University, Newark, New Jersey, USA
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8
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Computer-Aided Drug Designing. Adv Bioinformatics 2021. [DOI: 10.1007/978-981-33-6191-1_9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
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Loyo CL, Burton BM. Quantitative Transformation Efficiency Assay for Bacillus subtilis. Bio Protoc 2018; 8:e3109. [PMID: 34532552 DOI: 10.21769/bioprotoc.3109] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2018] [Revised: 03/13/2018] [Accepted: 03/26/2018] [Indexed: 11/02/2022] Open
Abstract
Bacillus subtilis (B. subtilis) is a model Gram-positive organism used to study a variety of physiological states and stress responses, one of which is the development of competence. Competence refers to the physiological state of a cell which allows it to be transformed naturally. Through induction of competence, the efficiency of natural transformation can be quantified by plating colony forming units (CFU) and transforming units (TFU). Here we describe a protocol for quantifying relative transformability using B. subtilis.
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Affiliation(s)
- Christian L Loyo
- Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Briana M Burton
- Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin, USA
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Sun D. Pull in and Push Out: Mechanisms of Horizontal Gene Transfer in Bacteria. Front Microbiol 2018; 9:2154. [PMID: 30237794 PMCID: PMC6135910 DOI: 10.3389/fmicb.2018.02154] [Citation(s) in RCA: 62] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2018] [Accepted: 08/22/2018] [Indexed: 01/06/2023] Open
Abstract
Horizontal gene transfer (HGT) plays an important role in bacterial evolution. It is well accepted that DNA is pulled/pushed into recipient cells by conserved membrane-associated DNA transport systems, which allow the entry of only single-stranded DNA (ssDNA). However, recent studies have uncovered a new type of natural bacterial transformation in which double-stranded DNA (dsDNA) is taken up into the cytoplasm, thus complementing the existing methods of DNA transfer among bacteria. Regulated by the stationary-phase regulators RpoS and cAMP receptor protein (CRP), Escherichia coli establishes competence for natural transformation with dsDNA, which occurs in agar plates. To pass across the outer membrane, a putative channel, which may compete for the substrate with the porin OmpA, may mediate the transfer of exogenous dsDNA into the cell. To pass across the inner membrane, dsDNA may be bound to the periplasmic protein YdcS, which delivers it into the inner membrane channel formed by YdcV. The discovery of cell-to-cell contact-dependent plasmid transformation implies the presence of additional mechanism(s) of transformation. This review will summarize the current knowledge about mechanisms of HGT with an emphasis on recent progresses regarding non-canonical mechanisms of natural transformation. Fully understanding the mechanisms of HGT will provide a foundation for monitoring and controlling multidrug resistance.
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Affiliation(s)
- Dongchang Sun
- College of Biotechnology and Bioengineering, Zhejiang University of Technology, Hangzhou, China
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Diallo A, Foster HR, Gromek KA, Perry TN, Dujeancourt A, Krasteva PV, Gubellini F, Falbel TG, Burton BM, Fronzes R. Bacterial transformation: ComFA is a DNA-dependent ATPase that forms complexes with ComFC and DprA. Mol Microbiol 2017; 105:741-754. [DOI: 10.1111/mmi.13732] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/13/2017] [Indexed: 12/28/2022]
Affiliation(s)
- Amy Diallo
- Institut Pasteur, G5 Groupe Biologie Structurale de la Sécrétion Bactérienne; Paris France
- CNRS, UMR3528, Institut Pasteur; 25-28 rue du Docteur Roux, Paris F-75015 France
- Université Pierre et Marie Curie; Paris France
| | | | | | - Thomas N. Perry
- Institut Pasteur, G5 Groupe Biologie Structurale de la Sécrétion Bactérienne; Paris France
- CNRS, UMR3528, Institut Pasteur; 25-28 rue du Docteur Roux, Paris F-75015 France
| | - Annick Dujeancourt
- Institut Pasteur, G5 Groupe Biologie Structurale de la Sécrétion Bactérienne; Paris France
- CNRS, UMR3528, Institut Pasteur; 25-28 rue du Docteur Roux, Paris F-75015 France
| | - Petya V. Krasteva
- Institut Pasteur, G5 Groupe Biologie Structurale de la Sécrétion Bactérienne; Paris France
- CNRS, UMR3528, Institut Pasteur; 25-28 rue du Docteur Roux, Paris F-75015 France
| | - Francesca Gubellini
- Institut Pasteur, G5 Groupe Biologie Structurale de la Sécrétion Bactérienne; Paris France
- CNRS, UMR3528, Institut Pasteur; 25-28 rue du Docteur Roux, Paris F-75015 France
| | | | | | - Rémi Fronzes
- Institut Pasteur, G5 Groupe Biologie Structurale de la Sécrétion Bactérienne; Paris France
- CNRS, UMR3528, Institut Pasteur; 25-28 rue du Docteur Roux, Paris F-75015 France
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