1
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Kishida K, Li YG, Ogawa-Kishida N, Khara P, Al Mamun AAM, Bosserman RE, Christie PJ. Chimeric systems composed of swapped Tra subunits between distantly-related F plasmids reveal striking plasticity among type IV secretion machines. PLoS Genet 2024; 20:e1011088. [PMID: 38437248 PMCID: PMC10939261 DOI: 10.1371/journal.pgen.1011088] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2023] [Revised: 03/14/2024] [Accepted: 02/20/2024] [Indexed: 03/06/2024] Open
Abstract
Bacterial type IV secretion systems (T4SSs) are a versatile family of macromolecular translocators, collectively able to recruit diverse DNA and protein substrates and deliver them to a wide range of cell types. Presently, there is little understanding of how T4SSs recognize substrate repertoires and form productive contacts with specific target cells. Although T4SSs are composed of a number of conserved subunits and adopt certain conserved structural features, they also display considerable compositional and structural diversity. Here, we explored the structural bases underlying the functional versatility of T4SSs through systematic deletion and subunit swapping between two conjugation systems encoded by the distantly-related IncF plasmids, pED208 and F. We identified several regions of intrinsic flexibility among the encoded T4SSs, as evidenced by partial or complete functionality of chimeric machines. Swapping of VirD4-like TraD type IV coupling proteins (T4CPs) yielded functional chimeras, indicative of relaxed specificity at the substrate-TraD and TraD-T4SS interfaces. Through mutational analyses, we further delineated domains of the TraD T4CPs contributing to recruitment of cognate vs heterologous DNA substrates. Remarkably, swaps of components comprising the outer membrane core complexes, a few F-specific subunits, or the TraA pilins supported DNA transfer in the absence of detectable pilus production. Among sequenced enterobacterial species in the NCBI database, we identified many strains that harbor two or more F-like plasmids and many F plasmids lacking one or more T4SS components required for self-transfer. We confirmed that host cells carrying co-resident, non-selftransmissible variants of pED208 and F elaborate chimeric T4SSs, as evidenced by transmission of both plasmids. We propose that T4SS plasticity enables the facile assembly of functional chimeras, and this intrinsic flexibility at the structural level can account for functional diversification of this superfamily over evolutionary time and, on a more immediate time-scale, to proliferation of transfer-defective MGEs in nature.
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Affiliation(s)
- Kouhei Kishida
- Department of Microbiology and Molecular Genetics, McGovern Medical School at UTHealth, Houston, Texas, United States of America
| | - Yang Grace Li
- Department of Microbiology and Molecular Genetics, McGovern Medical School at UTHealth, Houston, Texas, United States of America
| | - Natsumi Ogawa-Kishida
- Department of Microbiology and Molecular Genetics, McGovern Medical School at UTHealth, Houston, Texas, United States of America
| | - Pratick Khara
- Department of Microbiology and Molecular Genetics, McGovern Medical School at UTHealth, Houston, Texas, United States of America
| | - Abu Amar M. Al Mamun
- Department of Microbiology and Molecular Genetics, McGovern Medical School at UTHealth, Houston, Texas, United States of America
| | - Rachel E. Bosserman
- Department of Microbiology and Molecular Genetics, McGovern Medical School at UTHealth, Houston, Texas, United States of America
| | - Peter J. Christie
- Department of Microbiology and Molecular Genetics, McGovern Medical School at UTHealth, Houston, Texas, United States of America
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2
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Giengkam S, Kullapanich C, Wongsantichon J, Adcox HE, Gillespie JJ, Salje J. Orientia tsutsugamushi: comprehensive analysis of the mobilome of a highly fragmented and repetitive genome reveals the capacity for ongoing lateral gene transfer in an obligate intracellular bacterium. mSphere 2023; 8:e0026823. [PMID: 37850800 PMCID: PMC10732058 DOI: 10.1128/msphere.00268-23] [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: 05/15/2023] [Accepted: 08/22/2023] [Indexed: 10/19/2023] Open
Abstract
IMPORTANCE Obligate intracellular bacteria, or those only capable of growth inside other living cells, have limited opportunities for horizontal gene transfer with other microbes due to their isolated replicative niche. The human pathogen Ot, an obligate intracellular bacterium causing scrub typhus, encodes an unusually high copy number of a ~40 gene mobile genetic element that typically facilitates genetic transfer across microbes. This proliferated element is heavily degraded in Ot and previously assumed to be inactive. Here, we conducted a detailed analysis of this element in eight Ot strains and discovered two strains with at least one intact copy. This implies that the element is still capable of moving across Ot populations and suggests that the genome of this bacterium may be even more dynamic than previously appreciated. Our work raises questions about intracellular microbial evolution and sounds an alarm for gene-based efforts focused on diagnosing and combatting scrub typhus.
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Affiliation(s)
- Suparat Giengkam
- Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Chitrasak Kullapanich
- Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Jantana Wongsantichon
- Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Haley E. Adcox
- Department of Microbiology and Immunology, Virginia Commonwealth University Medical Center, School of Medicine, Richmond, Virginia, USA
| | - Joseph J. Gillespie
- Department of Microbiology and Immunology, School of Medicine, University of Maryland Baltimore, Baltimore, Maryland, USA
| | - Jeanne Salje
- Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- Department of Pathology, University of Cambridge, Cambridge, United Kingdom
- Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom
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3
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Kishida K, Li YG, Ogawa-Kishida N, Khara P, Al Mamun AAM, Bosserman RE, Christie PJ. Chimeric systems composed of swapped Tra subunits between distantly-related F plasmids reveal striking plasticity among type IV secretion machines. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.12.05.570194. [PMID: 38106057 PMCID: PMC10723329 DOI: 10.1101/2023.12.05.570194] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2023]
Abstract
Bacterial type IV secretion systems (T4SSs) are a versatile family of macromolecular translocators, collectively able to recruit diverse DNA and protein substrates and deliver them to a wide range of cell types. Presently, there is little understanding of how T4SSs recognize substrate repertoires and form productive contacts with specific target cells. Although T4SSs are composed of a number of conserved subunits and adopt certain conserved structural features, they also display considerable compositional and structural diversity. Here, we explored the structural bases underlying the functional versatility of T4SSs through systematic deletion and subunit swapping between two conjugation systems encoded by the distantly-related IncF plasmids, pED208 and F. We identified several regions of intrinsic flexibility among the encoded T4SSs, as evidenced by partial or complete functionality of chimeric machines. Swapping of VirD4-like TraD type IV coupling proteins (T4CPs) yielded functional chimeras, indicative of relaxed specificity at the substrate - TraD and TraD - T4SS interfaces. Through mutational analyses, we further delineated domains of the TraD T4CPs contributing to recruitment of cognate vs heterologous DNA substrates. Remarkably, swaps of components comprising the outer membrane core complexes, a few F-specific subunits, or the TraA pilins supported DNA transfer in the absence of detectable pilus production. Among sequenced enterobacterial species in the NCBI database, we identified many strains that harbor two or more F-like plasmids and many F plasmids lacking one or more T4SS components required for self-transfer. We confirmed that host cells carrying co-resident, non-selftransmissible variants of pED208 and F elaborate chimeric T4SSs, as evidenced by transmission of both plasmids. We propose that T4SS plasticity enables the facile assembly of functional chimeras, and this intrinsic flexibility at the structural level can account for functional diversification of this superfamily over evolutionary time and, on a more immediate time-scale, to proliferation of transfer-defective MGEs in nature.
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Affiliation(s)
- Kouhei Kishida
- Department of Microbiology and Molecular Genetics, McGovern Medical School at UTHealth, 6431 Fannin St, Houston, Texas 77030, United States of America
| | - Yang Grace Li
- Department of Microbiology and Molecular Genetics, McGovern Medical School at UTHealth, 6431 Fannin St, Houston, Texas 77030, United States of America
| | - Natsumi Ogawa-Kishida
- Department of Microbiology and Molecular Genetics, McGovern Medical School at UTHealth, 6431 Fannin St, Houston, Texas 77030, United States of America
| | - Pratick Khara
- Department of Microbiology and Molecular Genetics, McGovern Medical School at UTHealth, 6431 Fannin St, Houston, Texas 77030, United States of America
| | - Abu Amar M Al Mamun
- Department of Microbiology and Molecular Genetics, McGovern Medical School at UTHealth, 6431 Fannin St, Houston, Texas 77030, United States of America
| | - Rachel E. Bosserman
- Department of Microbiology and Molecular Genetics, McGovern Medical School at UTHealth, 6431 Fannin St, Houston, Texas 77030, United States of America
| | - Peter J. Christie
- Department of Microbiology and Molecular Genetics, McGovern Medical School at UTHealth, 6431 Fannin St, Houston, Texas 77030, United States of America
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Piccirilli A, Di Marcantonio S, Costantino V, Simonetti O, Busetti M, Luzzati R, Principe L, Di Domenico M, Rinaldi A, Cammà C, Perilli M. Identification of IncA Plasmid, Harboring blaVIM-1 Gene, in S. enterica Goldcoast ST358 and C. freundii ST62 Isolated in a Hospitalized Patient. Antibiotics (Basel) 2023; 12:1659. [PMID: 38136693 PMCID: PMC10741216 DOI: 10.3390/antibiotics12121659] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2023] [Revised: 11/21/2023] [Accepted: 11/23/2023] [Indexed: 12/24/2023] Open
Abstract
In the present study, we analyzed the genome of two S. enterica strains TS1 and TS2 from stool and blood cultures, respectively, and one strain of C. freundii TS3, isolated from a single hospitalized patient with acute myeloid leukemia. The S. enterica Goldcoast ST358 (O:8 (C2-C3) serogroup), sequenced by the MiSeq Illumina system, showed the presence of β-lactamase genes (blaVIM-1, blaSHV-12 and blaOXA-10), aadA1, ant(2″)-Ia, aac(6')-Iaa, aac(6')-Ib3, aac(6')-Ib-cr, qnrVC6, parC(T57S), and several incompatibility plasmids. A wide variety of insertion sequences (ISs) and transposon elements were identified. In C. freundii TS3, these were the blaVIM-1, blaCMY-150, and blaSHV-12, aadA1, aac(6')-Ib3, aac(6')-Ib-cr, mph(A), sul1, dfrA14, ARR-2, qnrVC6, and qnrB38. IncA plasmid isolated from E.coli/K12 transconjugant and C. freundii exhibited a sequence identity >99.9%. The transfer of IncA plasmid was evaluated by conjugation experiments.
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Affiliation(s)
- Alessandra Piccirilli
- Department of Biotechnological and Applied Clinical Sciences, University of L’Aquila, 67100 L’Aquila, Italy; (S.D.M.); (M.P.)
| | - Sascia Di Marcantonio
- Department of Biotechnological and Applied Clinical Sciences, University of L’Aquila, 67100 L’Aquila, Italy; (S.D.M.); (M.P.)
| | - Venera Costantino
- Microbiology Unit, Trieste University Hospital (ASUGI), 34125 Trieste, Italy; (V.C.); (M.B.)
| | - Omar Simonetti
- Infectious Diseases Unit, Trieste University Hospital (ASUGI), 34125 Trieste, Italy; (O.S.); (R.L.)
| | - Marina Busetti
- Microbiology Unit, Trieste University Hospital (ASUGI), 34125 Trieste, Italy; (V.C.); (M.B.)
| | - Roberto Luzzati
- Infectious Diseases Unit, Trieste University Hospital (ASUGI), 34125 Trieste, Italy; (O.S.); (R.L.)
| | - Luigi Principe
- Clinical Pathology and Microbiology Unit, “S. Giovanni di Dio” Hospital, 88900 Crotone, Italy;
| | - Marco Di Domenico
- Istituto Zooprofilattico Sperimentale dell’Abruzzo e del Molise, Campo Boario, 64100 Teramo, Italy; (M.D.D.); (A.R.); (C.C.)
| | - Antonio Rinaldi
- Istituto Zooprofilattico Sperimentale dell’Abruzzo e del Molise, Campo Boario, 64100 Teramo, Italy; (M.D.D.); (A.R.); (C.C.)
| | - Cesare Cammà
- Istituto Zooprofilattico Sperimentale dell’Abruzzo e del Molise, Campo Boario, 64100 Teramo, Italy; (M.D.D.); (A.R.); (C.C.)
| | - Mariagrazia Perilli
- Department of Biotechnological and Applied Clinical Sciences, University of L’Aquila, 67100 L’Aquila, Italy; (S.D.M.); (M.P.)
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5
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Kishida K, Bosserman RE, Harb L, Khara P, Song L, Hu B, Zeng L, Christie PJ. Contributions of F‐specific Subunits to the F
Plasmid‐Encoded
Type
IV
Secretion System and F pilus. Mol Microbiol 2022; 117:1275-1290. [DOI: 10.1111/mmi.14908] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Revised: 03/26/2022] [Accepted: 04/12/2022] [Indexed: 11/30/2022]
Affiliation(s)
- Kouhei Kishida
- Department of Microbiology and Molecular Genetics McGovern Medical School 6431 Fannin St, Houston, Texas 77030
| | - Rachel E. Bosserman
- Department of Microbiology and Molecular Genetics McGovern Medical School 6431 Fannin St, Houston, Texas 77030
- Current address: Department of Medicine, Division of Infectious Diseases Washington School of Medicine St. Louis, MO, 63110
| | - Laith Harb
- Department of Biochemistry and Biophysics, Texas A&M University College Station TX, 77843 USA
- Center for Phage Technology, Texas A&M University College Station TX, 77843 USA
| | - Pratick Khara
- Department of Microbiology and Molecular Genetics McGovern Medical School 6431 Fannin St, Houston, Texas 77030
| | - Liqiang Song
- Department of Microbiology and Molecular Genetics McGovern Medical School 6431 Fannin St, Houston, Texas 77030
| | - Bo Hu
- Department of Microbiology and Molecular Genetics McGovern Medical School 6431 Fannin St, Houston, Texas 77030
| | - Lanying Zeng
- Department of Biochemistry and Biophysics, Texas A&M University College Station TX, 77843 USA
- Center for Phage Technology, Texas A&M University College Station TX, 77843 USA
| | - Peter J. Christie
- Department of Microbiology and Molecular Genetics McGovern Medical School 6431 Fannin St, Houston, Texas 77030
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6
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Abstract
Horizontal transfer of bacterial plasmids generates genetic variability and contributes to the dissemination of the genes that enable bacterial cells to develop antimicrobial resistance (AMR). Several aspects of the conjugative process have long been known, namely, those related to the proteins that participate in the establishment of cell-to-cell contact and to the enzymatic processes associated with the processing of plasmid DNA and its transfer to the recipient cell. In this work, we describe the roles of newly identified proteins that influence the conjugation of several plasmids. Genes encoding high-molecular-weight bacterial proteins that contain one or several immunoglobulin-like domains (Big) are located in the transfer regions of several plasmids that usually harbor AMR determinants. These Big proteins are exported to the external medium and target two extracellular organelles: the flagella and conjugative pili. The plasmid gene-encoded Big proteins facilitate conjugation by reducing cell motility and facilitating cell-to-cell contact by binding both to the flagella and to the conjugative pilus. They use the same export machinery as that used by the conjugative pilus components. In the examples characterized in this paper, these proteins influence conjugation at environmental temperatures (i.e., 25°C). This suggests that they may play relevant roles in the dissemination of plasmids in natural environments. Taking into account that they interact with outer surface organelles, they could be targeted to control the dissemination of different bacterial plasmids carrying AMR determinants. IMPORTANCE Transmission of a plasmid from one bacterial cell to another, in several instances, underlies the dissemination of antimicrobial resistance (AMR) genes. The process requires well-characterized enzymatic machinery that facilitates cell-to-cell contact and the transfer of the plasmid. Our paper identifies novel plasmid gene-encoded high-molecular-weight proteins that contain an immunoglobulin-like domain and are required for plasmid transmission. They are encoded by genes on different groups of plasmids. These proteins are exported outside the cell. They bind to extracellular cell appendages such as the flagella and conjugative pili. Expression of these proteins reduces cell motility and increases the ability of the bacterial cells to transfer the plasmid. These proteins could be targeted with specific antibodies to combat infections caused by AMR microorganisms that harbor these plasmids.
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7
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Amin H, Ilangovan A, Costa TRD. Architecture of the outer-membrane core complex from a conjugative type IV secretion system. Nat Commun 2021; 12:6834. [PMID: 34824240 PMCID: PMC8617172 DOI: 10.1038/s41467-021-27178-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2021] [Accepted: 11/03/2021] [Indexed: 11/30/2022] Open
Abstract
Conjugation is one of the most important processes that bacteria utilize to spread antibiotic resistance genes among bacterial populations. Interbacterial DNA transfer requires a large double membrane-spanning nanomachine called the type 4 secretion system (T4SS) made up of the inner-membrane complex (IMC), the outer-membrane core complex (OMCC) and the conjugative pilus. The iconic F plasmid-encoded T4SS has been central in understanding conjugation for several decades, however atomic details of its structure are not known. Here, we report the structure of a complete conjugative OMCC encoded by the pED208 plasmid from E. coli, solved by cryo-electron microscopy at 3.3 Å resolution. This 2.1 MDa complex has a unique arrangement with two radial concentric rings, each having a different symmetry eventually contributing to remarkable differences in protein stoichiometry and flexibility in comparison to other OMCCs. Our structure suggests that F-OMCC is a highly dynamic complex, with implications for pilus extension and retraction during conjugation.
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Affiliation(s)
- Himani Amin
- grid.7445.20000 0001 2113 8111MRC Centre for Molecular Bacteriology and Infection, Department of Life Sciences, Imperial College, London, SW7 2AZ UK
| | - Aravindan Ilangovan
- School of Biological and Chemical Sciences, Queen Mary University of London, London, E1 4NS, UK.
| | - Tiago R. D. Costa
- grid.7445.20000 0001 2113 8111MRC Centre for Molecular Bacteriology and Infection, Department of Life Sciences, Imperial College, London, SW7 2AZ UK
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8
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Kumwenda GP, Sugawara Y, Akeda Y, Matsumoto Y, Motooka D, Tomono K, Hamada S. Genomic features of plasmids coding for KPC-2, NDM-5 or OXA-48 carbapenemases in Enterobacteriaceae from Malawi. J Antimicrob Chemother 2021; 76:267-270. [PMID: 32929493 DOI: 10.1093/jac/dkaa387] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Affiliation(s)
- Geoffrey Peterkins Kumwenda
- Japan-Thailand Research Collaboration Center on Emerging and Re-emerging Infections, Research Institute for Microbial Diseases, Osaka University, Osaka, Japan
- Department of Infection Control and Prevention, Osaka University Graduate School of Medicine, Osaka, Japan
- Microbiology Department, National Reference Laboratory, Community Health Sciences Unit, Ministry of Health, Lilongwe, Malawi
| | - Yo Sugawara
- Japan-Thailand Research Collaboration Center on Emerging and Re-emerging Infections, Research Institute for Microbial Diseases, Osaka University, Osaka, Japan
| | - Yukihiro Akeda
- Japan-Thailand Research Collaboration Center on Emerging and Re-emerging Infections, Research Institute for Microbial Diseases, Osaka University, Osaka, Japan
- Department of Infection Control and Prevention, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Yuki Matsumoto
- Department of Infection Metagenomics, Research Institute for Microbial Diseases, Osaka University, Osaka, Japan
| | - Daisuke Motooka
- Department of Infection Metagenomics, Research Institute for Microbial Diseases, Osaka University, Osaka, Japan
| | - Kazunori Tomono
- Department of Infection Control and Prevention, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Shigeyuki Hamada
- Japan-Thailand Research Collaboration Center on Emerging and Re-emerging Infections, Research Institute for Microbial Diseases, Osaka University, Osaka, Japan
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9
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Protein Dynamics in F-like Bacterial Conjugation. Biomedicines 2020; 8:biomedicines8090362. [PMID: 32961700 PMCID: PMC7555446 DOI: 10.3390/biomedicines8090362] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Revised: 09/15/2020] [Accepted: 09/17/2020] [Indexed: 01/21/2023] Open
Abstract
Efficient in silico development of novel antibiotics requires high-resolution, dynamic models of drug targets. As conjugation is considered the prominent contributor to the spread of antibiotic resistance genes, targeted drug design to disrupt vital components of conjugative systems has been proposed to lessen the proliferation of bacterial antibiotic resistance. Advancements in structural imaging techniques of large macromolecular complexes has accelerated the discovery of novel protein-protein interactions in bacterial type IV secretion systems (T4SS). The known structural information regarding the F-like T4SS components and complexes has been summarized in the following review, revealing a complex network of protein-protein interactions involving domains with varying degrees of disorder. Structural predictions were performed to provide insight on the dynamicity of proteins within the F plasmid conjugative system that lack structural information.
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10
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Koch B, Callaghan MM, Tellechea-Luzardo J, Seeger AY, Dillard JP, Krasnogor N. Protein interactions within and between two F-type type IV secretion systems. Mol Microbiol 2020; 114:823-838. [PMID: 32738086 DOI: 10.1111/mmi.14582] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2020] [Revised: 07/20/2020] [Accepted: 07/20/2020] [Indexed: 01/03/2023]
Abstract
Bacterial type IV secretion systems (T4SSs) can mediate conjugation. The T4SS from Neisseria gonorrhoeae possesses the unique ability to mediate DNA secretion into the extracellular environment. The N. gonorrhoeae T4SS can be grouped with F-type conjugative T4SSs based on homology. We tested 17 proteins important for DNA secretion by N. gonorrhoeae for protein interactions. The BACTH-TM bacterial two-hybrid system was successfully used to study periplasmic interactions. By determining if the same interactions were observed for F-plasmid T4SS proteins and when one interaction partner was replaced by the corresponding protein from the other T4SS, we aimed to identify features associated with the unique function of the N. gonorrhoeae T4SS as well as generic features of F-type T4SSs. For both systems, we observed already described interactions shared by homologs from other T4SSs as well as new and described interactions between F-type T4SS-specific proteins. Furthermore, we demonstrate, for the first-time, interactions between proteins with homology to the conserved T4SS outer membrane core proteins and F-type-specific proteins and we confirmed two of them by co-purification. The F-type-specific protein TraHN was found to localize to the outer membrane and the presence of significant amounts of TraHN in the outer membrane requires TraGN .
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Affiliation(s)
- Birgit Koch
- Interdisciplinary Computing and Complex BioSystems (ICOS), School of Computing Science, Newcastle University, Newcastle upon Tyne, UK
| | - Melanie M Callaghan
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, WI, USA
| | - Jonathan Tellechea-Luzardo
- Interdisciplinary Computing and Complex BioSystems (ICOS), School of Computing Science, Newcastle University, Newcastle upon Tyne, UK
| | - Ami Y Seeger
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, WI, USA
| | - Joseph P Dillard
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, WI, USA
| | - Natalio Krasnogor
- Interdisciplinary Computing and Complex BioSystems (ICOS), School of Computing Science, Newcastle University, Newcastle upon Tyne, UK
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11
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Pitt ME, Cao MD, Butler MS, Ramu S, Ganesamoorthy D, Blaskovich MAT, Coin LJM, Cooper MA. Octapeptin C4 and polymyxin resistance occur via distinct pathways in an epidemic XDR Klebsiella pneumoniae ST258 isolate. J Antimicrob Chemother 2020; 74:582-593. [PMID: 30445429 DOI: 10.1093/jac/dky458] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2018] [Revised: 10/09/2018] [Accepted: 10/09/2018] [Indexed: 12/12/2022] Open
Abstract
BACKGROUND Polymyxin B and E (colistin) have been pivotal in the treatment of XDR Gram-negative bacterial infections; however, resistance has emerged. A structurally related lipopeptide, octapeptin C4, has shown significant potency against XDR bacteria, including polymyxin-resistant strains, but its mode of action remains undefined. OBJECTIVES We sought to compare and contrast the acquisition of resistance in an XDR Klebsiella pneumoniae (ST258) clinical isolate in vitro with all three lipopeptides to potentially unveil variations in their mode of action. METHODS The isolate was exposed to increasing concentrations of polymyxins and octapeptin C4 over 20 days. Day 20 strains underwent WGS, complementation assays, antimicrobial susceptibility testing and lipid A analysis. RESULTS Twenty days of exposure to the polymyxins resulted in a 1000-fold increase in the MIC, whereas for octapeptin C4 a 4-fold increase was observed. There was no cross-resistance observed between the polymyxin- and octapeptin-resistant strains. Sequencing of polymyxin-resistant isolates revealed mutations in previously known resistance-associated genes, including crrB, mgrB, pmrB, phoPQ and yciM, along with novel mutations in qseC. Octapeptin C4-resistant isolates had mutations in mlaDF and pqiB, genes related to phospholipid transport. These genetic variations were reflected in distinct phenotypic changes to lipid A. Polymyxin-resistant isolates increased 4-amino-4-deoxyarabinose fortification of lipid A phosphate groups, whereas the lipid A of octapeptin C4-resistant strains harboured a higher abundance of hydroxymyristate and palmitoylate. CONCLUSIONS Octapeptin C4 has a distinct mode of action compared with the polymyxins, highlighting its potential as a future therapeutic agent to combat the increasing threat of XDR bacteria.
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Affiliation(s)
- Miranda E Pitt
- Institute for Molecular Bioscience, University of Queensland, Brisbane, Australia
| | - Minh Duc Cao
- Institute for Molecular Bioscience, University of Queensland, Brisbane, Australia
| | - Mark S Butler
- Institute for Molecular Bioscience, University of Queensland, Brisbane, Australia
| | - Soumya Ramu
- Institute for Molecular Bioscience, University of Queensland, Brisbane, Australia
| | - Devika Ganesamoorthy
- Institute for Molecular Bioscience, University of Queensland, Brisbane, Australia
| | - Mark A T Blaskovich
- Institute for Molecular Bioscience, University of Queensland, Brisbane, Australia
| | - Lachlan J M Coin
- Institute for Molecular Bioscience, University of Queensland, Brisbane, Australia
| | - Matthew A Cooper
- Institute for Molecular Bioscience, University of Queensland, Brisbane, Australia
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12
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Yuan W, Tian T, Yang Q, Riaz L. Transfer potentials of antibiotic resistance genes in Escherichia spp. strains from different sources. CHEMOSPHERE 2020; 246:125736. [PMID: 31896018 DOI: 10.1016/j.chemosphere.2019.125736] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2019] [Revised: 12/20/2019] [Accepted: 12/23/2019] [Indexed: 05/29/2023]
Abstract
Multidrug-resistant Escherichia coli and antibiotic-resistance genes (ARGs) present a danger to public health. However, information on the dissemination potentials of antibiotic resistance among bacteria from different environments is lacking. We isolated multiple antibiotic-resistant Escherichia spp. from animal farms, hospitals, and municipal wastewater-treatment plants (MWWTPs) using culture-based methods, and carried out resistance phenotype and gene analyses. Thirty-five isolates of multiple antibiotic-resistant Escherichia spp. were further screened to detect 61 ARGs, 18 mobile genetic elements (MGEs), and gene cassettes. The isolates from livestock manure and MWWTPs showed greater diversity in plasmid profiling than hospital wastewater. Each Escherichia sp. carried 21-26 ARGs and 8-12 MGEs. In addition, 11 gene cassettes were detected in 34 Escherichia isolates, with greater diversity in livestock manure and MWWTPs than in hospital wastewater. The results indicated that the potential for ARG transfer was higher in livestock manure and MWWTPs compared with human clinical sources, possibly related to the high occurrence of both residual antibiotics and heavy metals in these environments.
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Affiliation(s)
- Wei Yuan
- Henan International Joint Laboratory of Agricultural Microbial Ecology and Technology (Henan Provincial Department of Science and Technology), Henan Normal University, Xinxiang, 453007, China; School of Environmental and Municipal Engineering, North China University of Water Resources and Electric Power, Zhengzhou, 450046, Henan, China
| | - Tiantian Tian
- College of Life Sciences, Henan Normal University, Xinxiang, 453007, China
| | - Qingxiang Yang
- College of Life Sciences, Henan Normal University, Xinxiang, 453007, China; Henan International Joint Laboratory of Agricultural Microbial Ecology and Technology (Henan Provincial Department of Science and Technology), Henan Normal University, Xinxiang, 453007, China.
| | - Luqman Riaz
- College of Life Sciences, Henan Normal University, Xinxiang, 453007, China; Henan International Joint Laboratory of Agricultural Microbial Ecology and Technology (Henan Provincial Department of Science and Technology), Henan Normal University, Xinxiang, 453007, China
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13
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Wang H, Qi H, Gong S, Huang Z, Meng C, Zhang Y, Chen X, Jiao X. Fe 3O 4 composited with MoS 2 blocks horizontal gene transfer. Colloids Surf B Biointerfaces 2020; 185:110569. [PMID: 31629970 DOI: 10.1016/j.colsurfb.2019.110569] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2019] [Revised: 09/13/2019] [Accepted: 10/06/2019] [Indexed: 11/25/2022]
Abstract
In this study, we found that Fe3O4 promoted horizontal gene transfer (HGT), but when Fe3O4 was composited with MoS2, the Fe3O4@MoS2 nanocomposite interacting with bacteria significantly blocked the HGT in the conjugation system. qPCR was used to analyze the expression of genes belonging to the chromosome and plasmid in the conjugation system. Results demonstrated that Fe3O4@MoS2 inhibited conjugation by promoting the expression of the global regulatory gene (trbA) and inhibiting the expression of conjugative transfer genes involved in mating pair formation (traF, trbB), DNA replication (trfA), and porins (outer membrane protein (omp) A and ompC). All of these genes are related to the permeability of the cell membrane, except for trfA. The results showed that Fe3O4@MoS2 interacted with bacteria to decrease their permeability against exogenous DNA. MoS2 may play an essential role in the HGT-inhibiting activity of Fe3O4@MoS2. This study highlights the diverse biological properties of nano-materials and provides clues for nano-scientists to develop environmentally friendly materials.
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Affiliation(s)
- Honggui Wang
- Jiangsu Key Laboratory of Zoonosis, Yangzhou University, Yangzhou, Jiangsu, 225009, PR China; Key Laboratory of Prevention and Control of Biological Hazard Factors (Animal Origin) for Agrifood Safety and Quality, Ministry of Agriculture of China, Yangzhou University (26116120), Yangzhou, Jiangsu, 225009, PR China; School of Environmental Science and Engineering, Yangzhou University, 225127, Yangzhou, Jiangsu, PR China
| | - Huachen Qi
- School of Environmental Science and Engineering, Yangzhou University, 225127, Yangzhou, Jiangsu, PR China
| | - Shujun Gong
- School of Environmental Science and Engineering, Yangzhou University, 225127, Yangzhou, Jiangsu, PR China
| | - Zhihai Huang
- School of Environmental Science and Engineering, Yangzhou University, 225127, Yangzhou, Jiangsu, PR China
| | - Chuang Meng
- Jiangsu Key Laboratory of Zoonosis, Yangzhou University, Yangzhou, Jiangsu, 225009, PR China; Key Laboratory of Prevention and Control of Biological Hazard Factors (Animal Origin) for Agrifood Safety and Quality, Ministry of Agriculture of China, Yangzhou University (26116120), Yangzhou, Jiangsu, 225009, PR China
| | - Ya Zhang
- School of Environmental Science and Engineering, Yangzhou University, 225127, Yangzhou, Jiangsu, PR China.
| | - Xiang Chen
- Jiangsu Key Laboratory of Zoonosis, Yangzhou University, Yangzhou, Jiangsu, 225009, PR China; Key Laboratory of Prevention and Control of Biological Hazard Factors (Animal Origin) for Agrifood Safety and Quality, Ministry of Agriculture of China, Yangzhou University (26116120), Yangzhou, Jiangsu, 225009, PR China
| | - Xin'an Jiao
- Jiangsu Key Laboratory of Zoonosis, Yangzhou University, Yangzhou, Jiangsu, 225009, PR China; Key Laboratory of Prevention and Control of Biological Hazard Factors (Animal Origin) for Agrifood Safety and Quality, Ministry of Agriculture of China, Yangzhou University (26116120), Yangzhou, Jiangsu, 225009, PR China.
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14
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Mukherjee SK, Mukherjee M. Characterization and Bio-Typing of Multidrug Resistance Plasmids From Uropathogenic Escherichia coli Isolated From Clinical Setting. Front Microbiol 2019; 10:2913. [PMID: 31921080 PMCID: PMC6930805 DOI: 10.3389/fmicb.2019.02913] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2018] [Accepted: 12/03/2019] [Indexed: 12/30/2022] Open
Abstract
Urinary tract infection is primarily caused by Escherichia coli. Multidrug resistance and their rapid dissemination in this pathogenic microbe complicate therapeutic strategies and threaten public health. Conjugation systems responsible for interbacterial transmission of antibiotic resistance are plasmid-encoded and can be classified as the P, F, and I types. Specific pili types and pili associated proteins were related to the transfer among this gram-negative organism and were thought to depend on contacts created by these structures at the time of DNA transport. In this study, conjugation system types of the plasmids that harbor multidrug resistant genes (aac-1b-cr, oqxAB, qnrB, qnrS, bla TEM, bla OXA) amongst 19 E. coli uropathogenic isolates were characterized under ciprofloxacin/ceftazidime selection individually by pili and pili associated gene types. Investigations indicated incidence of single plasmid of multiple replicon type amongst the transconjugants. bla TEM, bla CTX-M, bla OXA, aac-1b-cr, oqxAB, qnrB, qnrS genes in varied combination were observed to be successfully co-transmitted against ceftazidme/ciprofloxacin selection. Seven primer pair sets were selected that encodes pili and pili associated genes (traF, trwJ, traE, trhE, traG, pilM, pilx4) by nucleotide database search tools using annotated plasmids of different incompatibility types to assign the conjugation system type of the transmissible resistant plasmids by PCR. traF was predominant irrespective of drug selection that indicated F-type conjugation system was responsible for transmission of resistant plasmids which results in the rapid dissemination of antibiotic resistance in the isolates screened. Therefore this is a first report of its kind that investigated pili and pili associated genes to bio-type multidrug resistant plasmids and their transmission in clinical settings amongst uropathogenic E. coli circulated in the eastern part of India.
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Affiliation(s)
| | - Mandira Mukherjee
- Department of Biochemistry and Medical Biotechnology, Calcutta School of Tropical Medicine, Kolkata, India
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15
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Magaziner SJ, Zeng Z, Chen B, Salmond GPC. The Prophages of Citrobacter rodentium Represent a Conserved Family of Horizontally Acquired Mobile Genetic Elements Associated with Enteric Evolution towards Pathogenicity. J Bacteriol 2019; 201:e00638-18. [PMID: 30782635 PMCID: PMC6456863 DOI: 10.1128/jb.00638-18] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2018] [Accepted: 01/23/2019] [Indexed: 01/08/2023] Open
Abstract
Prophage-mediated horizontal gene transfer (HGT) plays a key role in the evolution of bacteria, enabling access to new environmental niches, including pathogenicity. Citrobacter rodentium is a host-adapted intestinal mouse pathogen and important model organism for attaching and effacing (A/E) pathogens, including the clinically significant enterohaemorrhagic and enteropathogenic Escherichia coli (EHEC and EPEC, respectively). Even though C. rodentium contains 10 prophage genomic regions, including an active temperate phage, ΦNP, little was known regarding the nature of C. rodentium prophages in the bacterium's evolution toward pathogenicity. In this study, our characterization of ΦNP led to the discovery of a second, fully functional temperate phage, named ΦSM. We identify the bacterial host receptor for both phages as lipopolysaccharide (LPS). ΦNP and ΦSM are likely important mediators of HGT in C. rodentium Bioinformatic analysis of the 10 prophage regions reveals cargo genes encoding known virulence factors, including several type III secretion system (T3SS) effectors. C. rodentium prophages are conserved across a wide range of pathogenic enteric bacteria, including EPEC and EHEC as well as pathogenic strains of Salmonella enterica, Shigella boydii, and Klebsiella pneumoniae Phylogenetic analysis of core enteric backbone genes compared against prophage evolutionary models suggests that these prophages represent an important, conserved family of horizontally acquired enteric-bacterium-associated pathogenicity determinants. In addition to highlighting the transformative role of bacteriophage-mediated HGT in C. rodentium's evolution toward pathogenicity, these data suggest that the examination of conserved families of prophages in other pathogenic bacteria and disease outbreaks might provide deeper evolutionary and pathological insights otherwise obscured by more classical analysis.IMPORTANCE Bacteriophages are obligate intracellular parasites of bacteria. Some bacteriophages can confer novel bacterial phenotypes, including pathogenicity, through horizontal gene transfer (HGT). The pathogenic bacterium Citrobacter rodentium infects mice using mechanisms similar to those employed by human gastrointestinal pathogens, making it an important model organism. Here, we examined the 10 prophages of C. rodentium, investigating their roles in its evolution toward virulence. We characterized ΦNP and ΦSM, two endogenous active temperate bacteriophages likely important for HGT. We showed that the 10 prophages encode predicted virulence factors and are conserved within other intestinal pathogens. Phylogenetic analysis suggested that they represent a conserved family of horizontally acquired enteric-bacterium-associated pathogenic determinants. Consequently, similar analysis of prophage elements in other pathogens might further understanding of their evolution and pathology.
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Affiliation(s)
- Samuel J Magaziner
- Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | - Ziyue Zeng
- Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | - Bihe Chen
- Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | - George P C Salmond
- Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
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16
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Abstract
Transcription is a discontinuous process, where each nucleotide incorporation cycle offers a decision between elongation, pausing, halting, or termination. Many cis-acting regulatory RNAs, such as riboswitches, exert their influence over transcription elongation. Through such mechanisms, certain RNA elements can couple physiological or environmental signals to transcription attenuation, a process where cis-acting regulatory RNAs directly influence formation of transcription termination signals. However, through another regulatory mechanism called processive antitermination (PA), RNA polymerase can bypass termination sites over much greater distances than transcription attenuation. PA mechanisms are widespread in bacteria, although only a few classes have been discovered overall. Also, although traditional, signal-responsive riboswitches have not yet been discovered to promote PA, it is increasingly clear that small RNA elements are still oftentimes required. In some instances, small RNA elements serve as loading sites for cellular factors that promote PA. In other instances, larger, more complicated RNA elements participate in PA in unknown ways, perhaps even acting alone to trigger PA activity. These discoveries suggest that what is now needed is a systematic exploration of PA in bacteria, to determine how broadly these transcription elongation mechanisms are utilized, to reveal the diversity in their molecular mechanisms, and to understand the general logic behind their cellular applications. This review covers the known examples of PA regulatory mechanisms and speculates that they may be broadly important to bacteria.
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Affiliation(s)
- Jonathan R. Goodson
- The University of Maryland, Department of Cell Biology and Molecular Genetics, College Park, MD 20742
| | - Wade C. Winkler
- The University of Maryland, Department of Cell Biology and Molecular Genetics, College Park, MD 20742
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17
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Shala-Lawrence A, Bragagnolo N, Nowroozi-Dayeni R, Kheyson S, Audette GF. The interaction of TraW and TrbC is required to facilitate conjugation in F-like plasmids. Biochem Biophys Res Commun 2018; 503:2386-2392. [PMID: 29966652 DOI: 10.1016/j.bbrc.2018.06.166] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2018] [Accepted: 06/28/2018] [Indexed: 12/20/2022]
Abstract
Bacterial conjugation, such as that mediated by the E. coli F plasmid, is a main mechanism driving bacterial evolution. Two important proteins required for F-pilus assembly and DNA transfer proficiency are TraW and TrbC. As members of a larger complex, these proteins assemble into a type IV secretion system and are essential components of pore formation and mating pair stabilization between the donor and the recipient cells. In the current report, we demonstrate the physical interaction of TraW and TrbC, show that TraW preferentially interacts with the N-terminal domain of TrbC, and that this interaction is important in restoring conjugation in traW/trbC knockouts.
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Affiliation(s)
- Agnesa Shala-Lawrence
- Department of Chemistry & Centre for Research on Biomolecular Interactions, York University, 4700 Keele St., Toronto, ON, M3J 1P3, Canada
| | - Nicholas Bragagnolo
- Department of Chemistry & Centre for Research on Biomolecular Interactions, York University, 4700 Keele St., Toronto, ON, M3J 1P3, Canada
| | - Roksana Nowroozi-Dayeni
- Department of Chemistry & Centre for Research on Biomolecular Interactions, York University, 4700 Keele St., Toronto, ON, M3J 1P3, Canada
| | - Sasha Kheyson
- Department of Chemistry & Centre for Research on Biomolecular Interactions, York University, 4700 Keele St., Toronto, ON, M3J 1P3, Canada
| | - Gerald F Audette
- Department of Chemistry & Centre for Research on Biomolecular Interactions, York University, 4700 Keele St., Toronto, ON, M3J 1P3, Canada.
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18
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Swings T, Marciano DC, Atri B, Bosserman RE, Wang C, Leysen M, Bonte C, Schalck T, Furey I, Van den Bergh B, Verstraeten N, Christie PJ, Herman C, Lichtarge O, Michiels J. CRISPR-FRT targets shared sites in a knock-out collection for off-the-shelf genome editing. Nat Commun 2018; 9:2231. [PMID: 29884781 PMCID: PMC5993718 DOI: 10.1038/s41467-018-04651-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2018] [Accepted: 05/11/2018] [Indexed: 01/12/2023] Open
Abstract
CRISPR advances genome engineering by directing endonuclease sequence specificity with a guide RNA molecule (gRNA). For precisely targeting a gene for modification, each genetic construct requires a unique gRNA. By generating a gRNA against the flippase recognition target (FRT) site, a common genetic element shared by multiple genetic collections, CRISPR-FRT circumvents this design constraint to provide a broad platform for fast, scarless, off-the-shelf genome engineering.
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Affiliation(s)
- Toon Swings
- Centre of Microbial and Plant Genetics, KU Leuven - University of Leuven, Kasteelpark Arenberg 20, 3001, Leuven, Belgium
- Center for Microbiology, VIB, Kasteelpark Arenberg 20, 3001, Leuven, Belgium
| | - David C Marciano
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, 77030, USA
| | - Benu Atri
- Quantitative and Computational Biosciences, Baylor College of Medicine, Houston, TX, 77030, USA
| | - Rachel E Bosserman
- Department of Microbiology and Molecular Genetics, McGovern Medical School, Houston, TX, 77030, USA
| | - Chen Wang
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, 77030, USA
| | - Marlies Leysen
- Centre of Microbial and Plant Genetics, KU Leuven - University of Leuven, Kasteelpark Arenberg 20, 3001, Leuven, Belgium
| | - Camille Bonte
- Centre of Microbial and Plant Genetics, KU Leuven - University of Leuven, Kasteelpark Arenberg 20, 3001, Leuven, Belgium
| | - Thomas Schalck
- Centre of Microbial and Plant Genetics, KU Leuven - University of Leuven, Kasteelpark Arenberg 20, 3001, Leuven, Belgium
- Center for Microbiology, VIB, Kasteelpark Arenberg 20, 3001, Leuven, Belgium
| | - Ian Furey
- Department of Pharmacology, Baylor College of Medicine, Houston, TX, 77030, USA
| | - Bram Van den Bergh
- Centre of Microbial and Plant Genetics, KU Leuven - University of Leuven, Kasteelpark Arenberg 20, 3001, Leuven, Belgium
- Center for Microbiology, VIB, Kasteelpark Arenberg 20, 3001, Leuven, Belgium
| | - Natalie Verstraeten
- Centre of Microbial and Plant Genetics, KU Leuven - University of Leuven, Kasteelpark Arenberg 20, 3001, Leuven, Belgium
- Center for Microbiology, VIB, Kasteelpark Arenberg 20, 3001, Leuven, Belgium
| | - Peter J Christie
- Department of Microbiology and Molecular Genetics, McGovern Medical School, Houston, TX, 77030, USA
| | - Christophe Herman
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, 77030, USA
| | - Olivier Lichtarge
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, 77030, USA.
- Quantitative and Computational Biosciences, Baylor College of Medicine, Houston, TX, 77030, USA.
- Department of Pharmacology, Baylor College of Medicine, Houston, TX, 77030, USA.
- Computational and Integrative Biomedical Research Center, Baylor College of Medicine, Houston, TX, 77030, USA.
| | - Jan Michiels
- Centre of Microbial and Plant Genetics, KU Leuven - University of Leuven, Kasteelpark Arenberg 20, 3001, Leuven, Belgium.
- Center for Microbiology, VIB, Kasteelpark Arenberg 20, 3001, Leuven, Belgium.
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19
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Abstract
Escherichia coli and other Gram-negative and -positive bacteria employ type IV secretion systems (T4SSs) to translocate DNA and protein substrates, generally by contact-dependent mechanisms, to other cells. The T4SSs functionally encompass two major subfamilies, the conjugation systems and the effector translocators. The conjugation systems are responsible for interbacterial transfer of antibiotic resistance genes, virulence determinants, and genes encoding other traits of potential benefit to the bacterial host. The effector translocators are used by many Gram-negative pathogens for delivery of potentially hundreds of virulence proteins termed effectors to eukaryotic cells during infection. In E. coli and other species of Enterobacteriaceae, T4SSs identified to date function exclusively in conjugative DNA transfer. In these species, the plasmid-encoded systems can be classified as the P, F, and I types. The P-type systems are the simplest in terms of subunit composition and architecture, and members of this subfamily share features in common with the paradigmatic Agrobacterium tumefaciens VirB/VirD4 T4SS. This review will summarize our current knowledge of the E. coli systems and the A. tumefaciens P-type system, with emphasis on the structural diversity of the T4SSs. Ancestral P-, F-, and I-type systems were adapted throughout evolution to yield the extant effector translocators, and information about well-characterized effector translocators also is included to further illustrate the adaptive and mosaic nature of these highly versatile machines.
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20
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Salmonella genomic island 1 (SGI1) reshapes the mating apparatus of IncC conjugative plasmids to promote self-propagation. PLoS Genet 2017; 13:e1006705. [PMID: 28355215 PMCID: PMC5389848 DOI: 10.1371/journal.pgen.1006705] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2016] [Revised: 04/12/2017] [Accepted: 03/20/2017] [Indexed: 11/20/2022] Open
Abstract
IncC conjugative plasmids and Salmonella genomic island 1 (SGI1) and relatives are frequently associated with multidrug resistance of clinical isolates of pathogenic Enterobacteriaceae. SGI1 is specifically mobilized in trans by IncA and IncC plasmids (commonly referred to as A/C plasmids) following its excision from the chromosome, an event triggered by the transcriptional activator complex AcaCD encoded by these helper plasmids. Although SGI1 is not self-transmissible, it carries three genes, traNS, traHS and traGS, coding for distant homologs of the predicted mating pore subunits TraNC, TraHC and TraGC, respectively, encoded by A/C plasmids. Here we investigated the regulation of traNS and traHGS and the role of these three genes in the transmissibility of SGI1. Transcriptional fusion of the promoter sequences of traNS and traHGS to the reporter gene lacZ confirmed that expression of these genes is inducible by AcaCD. Mating experiments using combinations of deletion mutants of SGI1 and the helper IncC plasmid pVCR94 revealed complex interactions between these two mobile genetic elements. Whereas traNC and traHGC are essential for IncC plasmid transfer, SGI1 could rescue null mutants of each individual gene revealing that TraNS, TraHS and TraGS are functional proteins. Complementation assays of individual traC and traS mutants showed that not only do TraNS/HS/GS replace TraNC/HC/GC in the mating pore encoded by IncC plasmids but also that traGS and traHS are both required for SGI1 optimal transfer. In fact, remodeling of the IncC-encoded mating pore by SGI1 was found to be essential to enhance transfer rate of SGI1 over the helper plasmid. Furthermore, traGS was found to be crucial to allow DNA transfer between cells bearing IncC helper plasmids, thereby suggesting that by remodeling the mating pore SGI1 disables an IncC-encoded entry exclusion mechanism. Hence traS genes facilitate the invasion by SGI1 of cell populations bearing IncC plasmids. Acquisition and dissemination of multidrug resistance genes among Enterobacteriaceae is in part driven by IncA and IncC (A/C) conjugative plasmids and Salmonella genomic island 1 (SGI1). Although unrelated, SGI1 relies on the self-transmissible A/C plasmids to disseminate within bacterial populations. The mechanisms allowing SGI1 to hijack the mating apparatus synthesized by A/C plasmids have not been previously established. Here, we show that IncC plasmids trigger the expression of three SGI1-borne genes that code for functional mating pore subunits distantly related to those encoded by the IncC helper plasmids. Our results indicate that these subunits alter the mating pore encoded by IncC plasmids to ensure optimal transfer of SGI1 and promote SGI1 dissemination in cell populations harboring IncC plasmids. Apart from SGI1 and relatives, documented mobilizable genomic islands are not known to code for mating pore components, possibly because of redundancy with those encoded by helper conjugative elements. Instead they usually code for mobilization proteins such as a relaxase and auxiliary factors involved in DNA recognition, processing and docking to the mating pore encoded by their helper conjugative element. From an ecological and epidemiological perspective, the strategy used by SGI1 likely confers a strong competitive advantage to SGI1 over IncC plasmids in clinical settings and could account for the high prevalence of SGI1 and relatives in multidrug-resistant Salmonella enterica and Proteus mirabilis.
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21
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Lento C, Ferraro M, Wilson D, Audette GF. HDX-MS and deletion analysis of the type 4 secretion system protein TraF from the Escherichia coli F plasmid. FEBS Lett 2016; 590:376-86. [PMID: 26785931 DOI: 10.1002/1873-3468.12066] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2015] [Revised: 01/08/2016] [Accepted: 01/12/2016] [Indexed: 12/26/2022]
Abstract
Conjugative DNA transfer by the F-plasmid is achieved through a type IV secretion system (T4SS) encoded within the plasmid's transfer region; TraF is one of several F-T4SS proteins essential for F-pilus assembly. In order to identify regions of the protein important for TraF function, a series of deletion mutants were assessed for their ability to recover conjugative transfer in a traF knockout. Interestingly, modification of any region of TraF abolishes pilus synthesis, resulting in a loss of rescue of conjugative function. Dynamic analysis of TraF by time-resolved hydrogen-deuterium exchange revealed that the C-terminal region containing the predicted thioredoxin-like domain is quite structured, while the N-terminal region, predicted to interact with TraH in the intact F-T4SS, was more dynamic.
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Affiliation(s)
- Cristina Lento
- Department of Chemistry, York University, Toronto, ON, Canada
| | - Michele Ferraro
- Department of Chemistry, York University, Toronto, ON, Canada
| | - Derek Wilson
- Department of Chemistry, York University, Toronto, ON, Canada.,Centre for Research on Biomolecular Interactions, York University, Toronto, ON, Canada.,Centre for Research in Mass Spectrometry, York University, Toronto, ON, Canada
| | - Gerald F Audette
- Department of Chemistry, York University, Toronto, ON, Canada.,Centre for Research on Biomolecular Interactions, York University, Toronto, ON, Canada
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22
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Structural Insight into How Bacteria Prevent Interference between Multiple Divergent Type IV Secretion Systems. mBio 2015; 6:e01867-15. [PMID: 26646013 PMCID: PMC4676284 DOI: 10.1128/mbio.01867-15] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Prokaryotes use type IV secretion systems (T4SSs) to translocate substrates (e.g., nucleoprotein, DNA, and protein) and/or elaborate surface structures (i.e., pili or adhesins). Bacterial genomes may encode multiple T4SSs, e.g., there are three functionally divergent T4SSs in some Bartonella species (vir, vbh, and trw). In a unique case, most rickettsial species encode a T4SS (rvh) enriched with gene duplication. Within single genomes, the evolutionary and functional implications of cross-system interchangeability of analogous T4SS protein components remains poorly understood. To lend insight into cross-system interchangeability, we analyzed the VirB8 family of T4SS channel proteins. Crystal structures of three VirB8 and two TrwG Bartonella proteins revealed highly conserved C-terminal periplasmic domain folds and dimerization interfaces, despite tremendous sequence divergence. This implies remarkable structural constraints for VirB8 components in the assembly of a functional T4SS. VirB8/TrwG heterodimers, determined via bacterial two-hybrid assays and molecular modeling, indicate that differential expression of trw and vir systems is the likely barrier to VirB8-TrwG interchangeability. We also determined the crystal structure of Rickettsia typhi RvhB8-II and modeled its coexpressed divergent paralog RvhB8-I. Remarkably, while RvhB8-I dimerizes and is structurally similar to other VirB8 proteins, the RvhB8-II dimer interface deviates substantially from other VirB8 structures, potentially preventing RvhB8-I/RvhB8-II heterodimerization. For the rvh T4SS, the evolution of divergent VirB8 paralogs implies a functional diversification that is unknown in other T4SSs. Collectively, our data identify two different constraints (spatiotemporal for Bartonellatrw and vir T4SSs and structural for rvh T4SSs) that mediate the functionality of multiple divergent T4SSs within a single bacterium. Assembly of multiprotein complexes at the right time and at the right cellular location is a fundamentally important task for any organism. In this respect, bacteria that express multiple analogous type IV secretion systems (T4SSs), each composed of around 12 different components, face an overwhelming complexity. Our work here presents the first structural investigation on factors regulating the maintenance of multiple T4SSs within a single bacterium. The structural data imply that the T4SS-expressing bacteria rely on two strategies to prevent cross-system interchangeability: (i) tight temporal regulation of expression or (ii) rapid diversification of the T4SS components. T4SSs are ideal drug targets provided that no analogous counterparts are known from eukaryotes. Drugs targeting the barriers to cross-system interchangeability (i.e., regulators) could dysregulate the structural and functional independence of discrete systems, potentially creating interference that prevents their efficient coordination throughout bacterial infection.
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23
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Ramsey ME, Bender T, Klimowicz AK, Hackett KT, Yamamoto A, Jolicoeur A, Callaghan MM, Wassarman KM, van der Does C, Dillard JP. Targeted mutagenesis of intergenic regions in the Neisseria gonorrhoeae gonococcal genetic island reveals multiple regulatory mechanisms controlling type IV secretion. Mol Microbiol 2015; 97:1168-85. [PMID: 26076069 PMCID: PMC4652943 DOI: 10.1111/mmi.13094] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/14/2015] [Indexed: 12/30/2022]
Abstract
Gonococci secrete chromosomal DNA into the extracellular environment using a type IV secretion system (T4SS). The secreted DNA acts in natural transformation and initiates biofilm development. Although the DNA and its effects are detectable, structural components of the T4SS are present at very low levels, suggestive of uncharacterized regulatory control. We sought to better characterize the expression and regulation of T4SS genes and found that the four operons containing T4SS genes are transcribed at very different levels. Increasing transcription of two of the operons through targeted promoter mutagenesis did not increase DNA secretion. The stability and steady-state levels of two T4SS structural proteins were affected by a homolog of tail-specific protease. An RNA switch was also identified that regulates translation of a third T4SS operon. The switch mechanism relies on two putative stem-loop structures contained within the 5' untranslated region of the transcript, one of which occludes the ribosome binding site and start codon. Mutational analysis of these stem loops supports a model in which induction of an alternative structure relieves repression. Taken together, these results identify multiple layers of regulation, including transcriptional, translational and post-translational mechanisms controlling T4SS gene expression and DNA secretion.
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Affiliation(s)
- Meghan E. Ramsey
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison School of Medicine and Public Health, Madison, Wisconsin, USA
| | - Tobias Bender
- Department of Ecophysiology, Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
| | - Amy K. Klimowicz
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison School of Medicine and Public Health, Madison, Wisconsin, USA
| | - Kathleen T. Hackett
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison School of Medicine and Public Health, Madison, Wisconsin, USA
| | - Ami Yamamoto
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison School of Medicine and Public Health, Madison, Wisconsin, USA
| | - Adrienne Jolicoeur
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison School of Medicine and Public Health, Madison, Wisconsin, USA
| | - Melanie M. Callaghan
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison School of Medicine and Public Health, Madison, Wisconsin, USA
| | - Karen M. Wassarman
- Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Chris van der Does
- Department of Ecophysiology, Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
| | - Joseph P. Dillard
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison School of Medicine and Public Health, Madison, Wisconsin, USA
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Guglielmini J, Néron B, Abby SS, Garcillán-Barcia MP, de la Cruz F, Rocha EPC. Key components of the eight classes of type IV secretion systems involved in bacterial conjugation or protein secretion. Nucleic Acids Res 2014; 42:5715-27. [PMID: 24623814 PMCID: PMC4027160 DOI: 10.1093/nar/gku194] [Citation(s) in RCA: 146] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Conjugation of DNA through a type IV secretion system (T4SS) drives horizontal gene transfer. Yet little is known on the diversity of these nanomachines. We previously found that T4SS can be divided in eight classes based on the phylogeny of the only ubiquitous protein of T4SS (VirB4). Here, we use an ab initio approach to identify protein families systematically and specifically associated with VirB4 in each class. We built profiles for these proteins and used them to scan 2262 genomes for the presence of T4SS. Our analysis led to the identification of thousands of occurrences of 116 protein families for a total of 1623 T4SS. Importantly, we could identify almost always in our profiles the essential genes of well-studied T4SS. This allowed us to build a database with the largest number of T4SS described to date. Using profile–profile alignments, we reveal many new cases of homology between components of distant classes of T4SS. We mapped these similarities on the T4SS phylogenetic tree and thus obtained the patterns of acquisition and loss of these protein families in the history of T4SS. The identification of the key VirB4-associated proteins paves the way toward experimental analysis of poorly characterized T4SS classes.
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Affiliation(s)
- Julien Guglielmini
- Microbial Evolutionary Genomics, Institut Pasteur, Paris 75015, France UMR3525, CNRS, Paris 75015, France
| | - Bertrand Néron
- Centre d'Informatique pour les Biologistes, Institut Pasteur, Paris 75015, France
| | - Sophie S Abby
- Microbial Evolutionary Genomics, Institut Pasteur, Paris 75015, France UMR3525, CNRS, Paris 75015, France
| | - María Pilar Garcillán-Barcia
- Institute of Biomedicine and Biotechnology of Cantabria (CSIC-Sodercan-University of Cantabria), Santander 39011, Spain
| | - Fernando de la Cruz
- Institute of Biomedicine and Biotechnology of Cantabria (CSIC-Sodercan-University of Cantabria), Santander 39011, Spain
| | - Eduardo P C Rocha
- Microbial Evolutionary Genomics, Institut Pasteur, Paris 75015, France UMR3525, CNRS, Paris 75015, France
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Christie PJ, Whitaker N, González-Rivera C. Mechanism and structure of the bacterial type IV secretion systems. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2014; 1843:1578-91. [PMID: 24389247 DOI: 10.1016/j.bbamcr.2013.12.019] [Citation(s) in RCA: 194] [Impact Index Per Article: 19.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2013] [Revised: 12/20/2013] [Accepted: 12/23/2013] [Indexed: 01/25/2023]
Abstract
The bacterial type IV secretion systems (T4SSs) translocate DNA and protein substrates to bacterial or eukaryotic target cells generally by a mechanism dependent on direct cell-to-cell contact. The T4SSs encompass two large subfamilies, the conjugation systems and the effector translocators. The conjugation systems mediate interbacterial DNA transfer and are responsible for the rapid dissemination of antibiotic resistance genes and virulence determinants in clinical settings. The effector translocators are used by many Gram-negative bacterial pathogens for delivery of potentially hundreds of virulence proteins to eukaryotic cells for modulation of different physiological processes during infection. Recently, there has been considerable progress in defining the structures of T4SS machine subunits and large machine subassemblies. Additionally, the nature of substrate translocation sequences and the contributions of accessory proteins to substrate docking with the translocation channel have been elucidated. A DNA translocation route through the Agrobacterium tumefaciens VirB/VirD4 system was defined, and both intracellular (DNA ligand, ATP energy) and extracellular (phage binding) signals were shown to activate type IV-dependent translocation. Finally, phylogenetic studies have shed light on the evolution and distribution of T4SSs, and complementary structure-function studies of diverse systems have identified adaptations tailored for novel functions in pathogenic settings. This review summarizes the recent progress in our understanding of the architecture and mechanism of action of these fascinating machines, with emphasis on the 'archetypal' A. tumefaciens VirB/VirD4 T4SS and related conjugation systems. This article is part of a Special Issue entitled: Protein trafficking and secretion in bacteria. Guest Editors: Anastassios Economou and Ross Dalbey.
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Affiliation(s)
- Peter J Christie
- Department of Microbiology and Molecular Genetics, UT-Houston Medical School, 6431 Fannin, JFB1.765, Houston, TX 77030, USA.
| | - Neal Whitaker
- Department of Microbiology and Molecular Genetics, UT-Houston Medical School, 6431 Fannin, JFB1.765, Houston, TX 77030, USA
| | - Christian González-Rivera
- Department of Microbiology and Molecular Genetics, UT-Houston Medical School, 6431 Fannin, JFB1.765, Houston, TX 77030, USA
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F conjugation: Back to the beginning. Plasmid 2013; 70:18-32. [DOI: 10.1016/j.plasmid.2013.03.010] [Citation(s) in RCA: 107] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2012] [Revised: 03/26/2013] [Accepted: 03/28/2013] [Indexed: 11/19/2022]
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27
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Hemmis CW, Schildbach JF. Thioredoxin-like proteins in F and other plasmid systems. Plasmid 2013; 70:168-89. [PMID: 23721857 DOI: 10.1016/j.plasmid.2013.05.004] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2013] [Revised: 05/12/2013] [Accepted: 05/13/2013] [Indexed: 11/29/2022]
Abstract
Bacterial conjugation is the process by which a conjugative plasmid transfers from donor to recipient bacterium. During this process, single-stranded plasmid DNA is actively and specifically transported from the cytoplasm of the donor, through a large membrane-spanning assembly known as the pore complex, and into the cytoplasm of the recipient. In Gram negative bacteria, construction of the pore requires localization of a subset of structural and catalytically active proteins to the bacterial periplasm. Unlike the cytoplasm, the periplasm contains proteins that promote disulfide bond formation within or between cysteine-containing proteins. To ensure proper protein folding and assembly, bacteria employ periplasmic redox systems for thiol oxidation, disulfide bond/sulfenic acid reduction, and disulfide bond isomerization. Recent data suggest that plasmid-based proteins belonging to the disulfide bond formation family play an integral role in the conjugative process by serving as mediators in folding and/or assembly of pore complex proteins. Here we report the identification of 165 thioredoxin-like family members across 89 different plasmid systems. Using phylogenetic analysis, all but nine family members were categorized into thioredoxin-like subfamilies. In addition, we discuss the diversity, conservation, and putative roles of thioredoxin-like proteins in plasmid systems, which include homologs of DsbA, DsbB, DsbC, DsbD, DsbG, and CcmG from Escherichia coli, TlpA from Bradyrhizobium japonicum, Com1 from Coxiella burnetii, as well as TrbB and TraF from plasmid F, and the absolute conservation of a disulfide isomerase in plasmids containing homologs of the transfer proteins TraH, TraN, and TraU.
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Affiliation(s)
- Casey W Hemmis
- Department of Biology, The Johns Hopkins University, Baltimore, MD 21218, USA
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Ramsey ME, Hackett KT, Kotha C, Dillard JP. New complementation constructs for inducible and constitutive gene expression in Neisseria gonorrhoeae and Neisseria meningitidis. Appl Environ Microbiol 2012; 78:3068-78. [PMID: 22327577 PMCID: PMC3346468 DOI: 10.1128/aem.07871-11] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2011] [Accepted: 02/06/2012] [Indexed: 12/20/2022] Open
Abstract
We have created new complementation constructs for use in Neisseria gonorrhoeae and Neisseria meningitidis. The constructs contain regions of homology with the chromosome and direct the insertion of a gene of interest into the intergenic region between the genes iga and trpB. In order to increase the available options for gene expression in Neisseria, we designed the constructs to contain one of three different promoters. One of the constructs contains the isopropyl-β-d-thiogalactopyranoside-inducible lac promoter, which has been widely used in Neisseria. We also designed a construct that contains the strong, constitutive promoter from the gonococcal opaB gene. The third construct contains a tetracycline-inducible promoter, a novel use of this promoter in Neisseria. We demonstrate that anhydrotetracycline can be used to induce gene expression in the pathogenic Neisseria at very low concentrations and without negatively affecting the growth of the organisms. We use these constructs to complement an arginine auxotrophy in N. gonorrhoeae as well as to express a translational fusion of alkaline phosphatase with TraW. TraW is a component of the gonococcal type IV secretion system, and we demonstrate that TraW localizes to the periplasm.
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Affiliation(s)
- Meghan E Ramsey
- Department of Medical Microbiology and Immunology, University of Wisconsin—Madison School of Medicine and Public Health, Madison, Wisconsin, USA
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TrbB from conjugative plasmid F is a structurally distinct disulfide isomerase that requires DsbD for redox state maintenance. J Bacteriol 2011; 193:4588-97. [PMID: 21742866 DOI: 10.1128/jb.00351-11] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
TrbB, a periplasmic protein encoded by the conjugative plasmid F, has a predicted thioredoxin-like fold and possesses a C-X-X-C redox active site motif. TrbB may function in the conjugative process by serving as a disulfide bond isomerase, facilitating proper folding of a subset of F-plasmid-encoded proteins in the periplasm. Previous studies have demonstrated that a ΔtrbB F plasmid in Escherichia coli lacking DsbC(E.coli), its native disulfide bond isomerase, experiences a 10-fold decrease in mating efficiency but have not provided direct evidence for disulfide bond isomerase activity. Here we demonstrate that trbB can partially restore transfer of a variant of the distantly related R27 plasmid when both chromosomal and plasmid genes encoding disulfide bond isomerases have been disrupted. In addition, we show that TrbB displays both disulfide bond isomerase and reductase activities on substrates not involved in the conjugative process. Unlike canonical members of the disulfide bond isomerase family, secondary structure predictions suggest that TrbB lacks both an N-terminal dimerization domain and an α-helical domain found in other disulfide bond isomerases. Phylogenetic analyses support the conclusion that TrbB belongs to a unique family of plasmid-based disulfide isomerases. Interestingly, although TrbB diverges structurally from other disulfide bond isomerases, we show that like those isomerases, TrbB relies on DsbD from E. coli for maintenance of its C-X-X-C redox active site motif.
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