1
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Blanco P, Trigo da Roza F, Toribio-Celestino L, García-Pastor L, Caselli N, Morón Á, Ojeda F, Darracq B, Vergara E, Amaro F, San Millán Á, Skovgaard O, Mazel D, Loot C, Escudero JA. Chromosomal integrons are genetically and functionally isolated units of genomes. Nucleic Acids Res 2024:gkae866. [PMID: 39385642 DOI: 10.1093/nar/gkae866] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2024] [Revised: 09/17/2024] [Accepted: 09/23/2024] [Indexed: 10/12/2024] Open
Abstract
Integrons are genetic elements that increase the evolvability of bacteria by capturing new genes and stockpiling them in arrays. Sedentary chromosomal integrons (SCIs) can be massive and highly stabilized structures encoding hundreds of genes, whose function remains generally unknown. SCIs have co-evolved with the host for aeons and are highly intertwined with their physiology from a mechanistic point of view. But, paradoxically, other aspects, like their variable content and location within the genome, suggest a high genetic and functional independence. In this work, we have explored the connection of SCIs to their host genome using as a model the Superintegron (SI), a 179-cassette long SCI in the genome of Vibrio cholerae N16961. We have relocated and deleted the SI using SeqDelTA, a novel method that allows to counteract the strong stabilization conferred by toxin-antitoxin systems within the array. We have characterized in depth the impact in V. cholerae's physiology, measuring fitness, chromosome replication dynamics, persistence, transcriptomics, phenomics, natural competence, virulence and resistance against protist grazing. The deletion of the SI did not produce detectable effects in any condition, proving that-despite millions of years of co-evolution-SCIs are genetically and functionally isolated units of genomes.
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Affiliation(s)
- Paula Blanco
- Molecular Basis of Adaptation, Departamento de Sanidad Animal, Universidad Complutense de Madrid, Madrid 28040, Spain
- VISAVET Health Surveillance Centre, Universidad Complutense de Madrid, Madrid 28040, Spain
| | - Filipa Trigo da Roza
- Molecular Basis of Adaptation, Departamento de Sanidad Animal, Universidad Complutense de Madrid, Madrid 28040, Spain
- VISAVET Health Surveillance Centre, Universidad Complutense de Madrid, Madrid 28040, Spain
| | - Laura Toribio-Celestino
- Departamento de Microbiología Microbiana, Centro Nacional de Biotecnología-CSIC, Madrid 28049, Spain
| | - Lucía García-Pastor
- Molecular Basis of Adaptation, Departamento de Sanidad Animal, Universidad Complutense de Madrid, Madrid 28040, Spain
- VISAVET Health Surveillance Centre, Universidad Complutense de Madrid, Madrid 28040, Spain
| | - Niccolò Caselli
- Departamento de Química Física, Universidad Complutense de Madrid, Madrid 28040, Spain
| | - Álvaro Morón
- Departamento de Genética, Fisiología y Microbiología, Facultad de Ciencias Biológicas, Universidad Complutense de Madrid, Madrid 28040, Spain
| | - Francisco Ojeda
- Molecular Basis of Adaptation, Departamento de Sanidad Animal, Universidad Complutense de Madrid, Madrid 28040, Spain
- VISAVET Health Surveillance Centre, Universidad Complutense de Madrid, Madrid 28040, Spain
| | - Baptiste Darracq
- Institut Pasteur, Université Paris Cité, CNRS UMR3525, Unité Plasticité du Génome Bactérien, 75015 Paris, France
- Sorbonne Université, ED515, F-75005 Paris, France
| | - Ester Vergara
- Molecular Basis of Adaptation, Departamento de Sanidad Animal, Universidad Complutense de Madrid, Madrid 28040, Spain
- VISAVET Health Surveillance Centre, Universidad Complutense de Madrid, Madrid 28040, Spain
| | - Francisco Amaro
- Departamento de Genética, Fisiología y Microbiología, Facultad de Ciencias Biológicas, Universidad Complutense de Madrid, Madrid 28040, Spain
| | - Álvaro San Millán
- Departamento de Microbiología Microbiana, Centro Nacional de Biotecnología-CSIC, Madrid 28049, Spain
| | - Ole Skovgaard
- Department of Science and Environment, Roskilde University, 4000 Roskilde, Denmark
| | - Didier Mazel
- Institut Pasteur, Université Paris Cité, CNRS UMR3525, Unité Plasticité du Génome Bactérien, 75015 Paris, France
| | - Céline Loot
- Institut Pasteur, Université Paris Cité, CNRS UMR3525, Unité Plasticité du Génome Bactérien, 75015 Paris, France
| | - José Antonio Escudero
- Molecular Basis of Adaptation, Departamento de Sanidad Animal, Universidad Complutense de Madrid, Madrid 28040, Spain
- VISAVET Health Surveillance Centre, Universidad Complutense de Madrid, Madrid 28040, Spain
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2
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Loot C, Millot GA, Richard E, Littner E, Vit C, Lemoine F, Néron B, Cury J, Darracq B, Niault T, Lapaillerie D, Parissi V, Rocha EPC, Mazel D. Integron cassettes integrate into bacterial genomes via widespread non-classical attG sites. Nat Microbiol 2024; 9:228-240. [PMID: 38172619 DOI: 10.1038/s41564-023-01548-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2023] [Accepted: 11/07/2023] [Indexed: 01/05/2024]
Abstract
Integrons are genetic elements involved in bacterial adaptation which capture, shuffle and express genes encoding adaptive functions embedded in cassettes. These events are governed by the integron integrase through site-specific recombination between attC and attI integron sites. Using computational and molecular genetic approaches, here we demonstrate that the integrase also catalyses cassette integration into bacterial genomes outside of its known att sites. Once integrated, these cassettes can be expressed if located near bacterial promoters and can be excised at the integration point or outside, inducing chromosomal modifications in the latter case. Analysis of more than 5 × 105 independent integration events revealed a very large genomic integration landscape. We identified consensus recombination sequences, named attG sites, which differ greatly in sequence and structure from classical att sites. These results unveil an alternative route for dissemination of adaptive functions in bacteria and expand the role of integrons in bacterial evolution.
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Affiliation(s)
- Céline Loot
- Institut Pasteur, Université Paris Cité, CNRS UMR 3525, Unité Plasticité du Génome Bactérien, Paris, France.
| | - Gael A Millot
- Institut Pasteur, Université Paris Cité, Bioinformatics and Biostatistics Hub, Paris, France
| | - Egill Richard
- Institut Pasteur, Université Paris Cité, CNRS UMR 3525, Unité Plasticité du Génome Bactérien, Paris, France
- Sorbonne Université, Collège Doctoral, Paris, France
| | - Eloi Littner
- Sorbonne Université, Collège Doctoral, Paris, France
- DGA CBRN Defence, Vert-le-Petit, France
- Institut Pasteur, Université Paris Cité, CNRS UMR 3525, Microbial Evolutionary Genomics, Paris, France
| | - Claire Vit
- Institut Pasteur, Université Paris Cité, CNRS UMR 3525, Unité Plasticité du Génome Bactérien, Paris, France
- Sorbonne Université, Collège Doctoral, Paris, France
| | - Frédéric Lemoine
- Institut Pasteur, Université Paris Cité, Bioinformatics and Biostatistics Hub, Paris, France
| | - Bertrand Néron
- Institut Pasteur, Université Paris Cité, Bioinformatics and Biostatistics Hub, Paris, France
| | - Jean Cury
- Université Paris-Saclay, Inria, Laboratoire de Recherche en Informatique, CNRS UMR 8623, Orsay, France
| | - Baptiste Darracq
- Institut Pasteur, Université Paris Cité, CNRS UMR 3525, Unité Plasticité du Génome Bactérien, Paris, France
- Sorbonne Université, Collège Doctoral, Paris, France
| | - Théophile Niault
- Institut Pasteur, Université Paris Cité, CNRS UMR 3525, Unité Plasticité du Génome Bactérien, Paris, France
- Sorbonne Université, Collège Doctoral, Paris, France
| | - Delphine Lapaillerie
- Université de Bordeaux, Fundamental Microbiology and Pathogenicity Laboratory, CNRS UMR 5234, Département de Sciences Biologiques et Médicales, Bordeaux, France
- Viral DNA Integration and Chromatin Dynamics Network (DyNAVir), Bordeaux, France
| | - Vincent Parissi
- Université de Bordeaux, Fundamental Microbiology and Pathogenicity Laboratory, CNRS UMR 5234, Département de Sciences Biologiques et Médicales, Bordeaux, France
- Viral DNA Integration and Chromatin Dynamics Network (DyNAVir), Bordeaux, France
| | - Eduardo P C Rocha
- Institut Pasteur, Université Paris Cité, CNRS UMR 3525, Microbial Evolutionary Genomics, Paris, France
| | - Didier Mazel
- Institut Pasteur, Université Paris Cité, CNRS UMR 3525, Unité Plasticité du Génome Bactérien, Paris, France
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3
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Baltazar-Cruz J, Rojas-Rios R, Larios-Serrato V, Mendoza-Sanchez I, Curiel-Quesada E, Pérez-Valdespino A. A Class 4-like Chromosomal Integron Found in Aeromonas sp. Genomospecies paramedia Isolated from Human Feces. Microorganisms 2023; 11:2548. [PMID: 37894206 PMCID: PMC10609294 DOI: 10.3390/microorganisms11102548] [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: 09/08/2023] [Revised: 09/29/2023] [Accepted: 10/12/2023] [Indexed: 10/29/2023] Open
Abstract
Integrons are genetic elements that store, express and exchange gene cassettes. These elements are characterized by containing a gene that codes for an integrase (intI), a cassette integration site (attI) and a variable region holding the cassettes. Using bioinformatics and molecular biology methods, a functional integron found in Aeromonas sp. 3925, a strain isolated from diarrheal stools, is described. To confirm the integron class, a phylogenetic analysis with amino acid sequences was conducted. The integrase was associated to class 4 integrases; however, it is clearly different from them. Thus, we classified the associated element as a class 4-like integron. We found that the integrase activity is not under the control of the SOS or catabolic repression, since the expression was not increased in the presence of mitomycin or arabinose. The class-4-like integron is located on the chromosome and contains two well-defined gene cassettes: aadA1 that confers resistance to streptomycin and lpt coding for a lipoprotein. It also includes eight Open Reading frames (ORFs) with unknown functions. The strain was characterized through a Multilocus Phylogenetic Analyses (MLPA) of the gyrB, gyrA, rpoD, recA, dnaJ and dnaX genes. The phylogenetic results grouped it into a different clade from the species already reported, making it impossible to assign a species. We resorted to undertaking complete genome sequencing and a phylogenomic analysis. Aeromonas sp. 3925 is related to A. media and A. rivipollensis clusters, but it is clearly different from these species. In silico DNA-DNA hybridization (isDDH) and Average Nucleotide Identity (ANI) analyses suggested that this isolate belongs to the genomospecies paramedia. This paper describes the first class 4-like integron in Aeromonas and contributes to the establishment of genomospecies paramedia.
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Affiliation(s)
- Jesús Baltazar-Cruz
- Department of Biochemistry, Escuela Nacional de Ciencias Biológicas del Instituto Politécnico Nacional, Prolongación de Carpio y Plan de Ayala S/N, Col. Santo Tomás, Mexico City 11340, Mexico; (J.B.-C.); (R.R.-R.); (V.L.-S.)
| | - Rogelio Rojas-Rios
- Department of Biochemistry, Escuela Nacional de Ciencias Biológicas del Instituto Politécnico Nacional, Prolongación de Carpio y Plan de Ayala S/N, Col. Santo Tomás, Mexico City 11340, Mexico; (J.B.-C.); (R.R.-R.); (V.L.-S.)
| | - Violeta Larios-Serrato
- Department of Biochemistry, Escuela Nacional de Ciencias Biológicas del Instituto Politécnico Nacional, Prolongación de Carpio y Plan de Ayala S/N, Col. Santo Tomás, Mexico City 11340, Mexico; (J.B.-C.); (R.R.-R.); (V.L.-S.)
| | - Itza Mendoza-Sanchez
- Department of Environmental & Occupational Health, Texas A&M University School of Public Health, College Station, TX 77843, USA;
| | - Everardo Curiel-Quesada
- Department of Biochemistry, Escuela Nacional de Ciencias Biológicas del Instituto Politécnico Nacional, Prolongación de Carpio y Plan de Ayala S/N, Col. Santo Tomás, Mexico City 11340, Mexico; (J.B.-C.); (R.R.-R.); (V.L.-S.)
| | - Abigail Pérez-Valdespino
- Department of Biochemistry, Escuela Nacional de Ciencias Biológicas del Instituto Politécnico Nacional, Prolongación de Carpio y Plan de Ayala S/N, Col. Santo Tomás, Mexico City 11340, Mexico; (J.B.-C.); (R.R.-R.); (V.L.-S.)
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4
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Zhang S, Li T, Hu J, Li K, Liu D, Li H, Wang F, Chen D, Zhang Z, Fan Q, Cui X, Che R. Reforestation substantially changed the soil antibiotic resistome and its relationships with metal resistance genes, mobile genetic elements, and pathogens. JOURNAL OF ENVIRONMENTAL MANAGEMENT 2023; 342:118037. [PMID: 37178462 DOI: 10.1016/j.jenvman.2023.118037] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2023] [Revised: 04/13/2023] [Accepted: 04/25/2023] [Indexed: 05/15/2023]
Abstract
Revealing the effects of reforestation on soil antibiotic resistome is essential for assessing ecosystem health, yet related studies remain scarce. Here, to determine the responses of the soil antibiotic resistome to reforestation, 30 pairs of cropland and forest soil samples were collected from southwestern China, a region with high environmental heterogeneity. All the forests had been derived from croplands more than one decade ago. The diversity and abundance of soil antibiotic resistance genes (ARGs), metal resistance genes (MRGs), mobile genetic elements (MGEs), and pathogens were determined by metagenomic sequencing and real-time PCR. The results showed that reforestation significantly increased soil microbial abundance and the contents of Cu, total carbon, total nitrogen, total organic carbon, and ammonium nitrogen. Nevertheless, it decreased the contents of soil Zn, Ba, nitrate nitrogen, and available phosphorus. The main soil ARGs identified in this region were vancomycin, multidrug, and bacitracin resistance genes. Reforestation significantly increased the soil ARG abundance by 62.58%, while it decreased the ARG richness by 16.50%. Reforestation exerted no significant effects on the abundance of heavy metal resistance genes and pathogens, but it doubled the abundance of MGEs. Additionally, reforestation substantially decreased the co-occurrence frequencies of ARGs with MRGs and pathogens. In contrast, the correlation between ARGs and MGEs was greatly enhanced by reforestation. Similarly, the correlations between soil ARG abundance and environmental factors were also strengthened by reforestation. These findings suggest that reforestation can substantially affect the soil antibiotic resistome and exerts overall positive effects on soil health by decreasing ARG richness, providing critical information for assessing the effects of "grain for green" project on soil health.
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Affiliation(s)
- Song Zhang
- Institute of International Rivers and Eco-security, Yunnan Key Laboratory of International Rivers and Transboundary Eco-Security, Yunnan University, Kunming, 650500, China; State Key Laboratory of Pollution Control & Resource Reuse, School of the Environment, Nanjing University, Nanjing, 210023, China
| | - Ting Li
- Institute of International Rivers and Eco-security, Yunnan Key Laboratory of International Rivers and Transboundary Eco-Security, Yunnan University, Kunming, 650500, China; College of Life Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Jinming Hu
- Institute of International Rivers and Eco-security, Yunnan Key Laboratory of International Rivers and Transboundary Eco-Security, Yunnan University, Kunming, 650500, China
| | - Kexin Li
- Laboratory of Wetland Ecology and Environment, Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun, 130102, China
| | - Dong Liu
- School of Life Sciences, Yunnan University, Kunming, 650091, China
| | - Haixia Li
- Faculty of Land Resource Engineering, Kunming University of Science and Technology, Kunming, 650093, China
| | - Fang Wang
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Danhong Chen
- Institute of International Rivers and Eco-security, Yunnan Key Laboratory of International Rivers and Transboundary Eco-Security, Yunnan University, Kunming, 650500, China
| | - Zejin Zhang
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Qiuping Fan
- Institute of International Rivers and Eco-security, Yunnan Key Laboratory of International Rivers and Transboundary Eco-Security, Yunnan University, Kunming, 650500, China
| | - Xiaoyong Cui
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Rongxiao Che
- Institute of International Rivers and Eco-security, Yunnan Key Laboratory of International Rivers and Transboundary Eco-Security, Yunnan University, Kunming, 650500, China.
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5
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Qi Q, Rajabal V, Ghaly TM, Tetu SG, Gillings MR. Identification of integrons and gene cassette-associated recombination sites in bacteriophage genomes. Front Microbiol 2023; 14:1091391. [PMID: 36744093 PMCID: PMC9892861 DOI: 10.3389/fmicb.2023.1091391] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2022] [Accepted: 01/05/2023] [Indexed: 01/20/2023] Open
Abstract
Bacteriophages are versatile mobile genetic elements that play key roles in driving the evolution of their bacterial hosts through horizontal gene transfer. Phages co-evolve with their bacterial hosts and have plastic genomes with extensive mosaicism. In this study, we present bioinformatic and experimental evidence that temperate and virulent (lytic) phages carry integrons, including integron-integrase genes, attC/attI recombination sites and gene cassettes. Integrons are normally found in Bacteria, where they capture, express and re-arrange mobile gene cassettes via integron-integrase activity. We demonstrate experimentally that a panel of attC sites carried in virulent phage can be recognized by the bacterial class 1 integron-integrase (IntI1) and then integrated into the paradigmatic attI1 recombination site using an attC x attI recombination assay. With an increasing number of phage genomes projected to become available, more phage-associated integrons and their components will likely be identified in the future. The discovery of integron components in bacteriophages establishes a new route for lateral transfer of these elements and their cargo genes between bacterial host cells.
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Affiliation(s)
- Qin Qi
- School of Natural Sciences, Macquarie University, Sydney, NSW, Australia,*Correspondence: Qin Qi, ✉
| | - Vaheesan Rajabal
- School of Natural Sciences, Macquarie University, Sydney, NSW, Australia,ARC Centre of Excellence in Synthetic Biology, Macquarie University, Sydney, NSW, Australia
| | - Timothy M. Ghaly
- School of Natural Sciences, Macquarie University, Sydney, NSW, Australia
| | - Sasha G. Tetu
- School of Natural Sciences, Macquarie University, Sydney, NSW, Australia,ARC Centre of Excellence in Synthetic Biology, Macquarie University, Sydney, NSW, Australia
| | - Michael R. Gillings
- School of Natural Sciences, Macquarie University, Sydney, NSW, Australia,ARC Centre of Excellence in Synthetic Biology, Macquarie University, Sydney, NSW, Australia
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Hipólito A, García-Pastor L, Blanco P, Trigo da Roza F, Kieffer N, Vergara E, Jové T, Álvarez J, Escudero J. The expression of aminoglycoside resistance genes in integron cassettes is not controlled by riboswitches. Nucleic Acids Res 2022; 50:8566-8579. [PMID: 35947699 PMCID: PMC9410878 DOI: 10.1093/nar/gkac662] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2022] [Revised: 07/11/2022] [Accepted: 07/22/2022] [Indexed: 12/24/2022] Open
Abstract
Regulation of gene expression is a key factor influencing the success of antimicrobial resistance determinants. A variety of determinants conferring resistance against aminoglycosides (Ag) are commonly found in clinically relevant bacteria, but whether their expression is regulated or not is controversial. The expression of several Ag resistance genes has been reported to be controlled by a riboswitch mechanism encoded in a conserved sequence. Yet this sequence corresponds to the integration site of an integron, a genetic platform that recruits genes of different functions, making the presence of such a riboswitch counterintuitive. We provide, for the first time, experimental evidence against the existence of such Ag-sensing riboswitch. We first tried to reproduce the induction of the well characterized aacA5 gene using its native genetic environment, but were unsuccessful. We then broadened our approach and analyzed the inducibility of all AgR genes encoded in integrons against a variety of antibiotics. We could not observe biologically relevant induction rates for any gene in the presence of several aminoglycosides. Instead, unrelated antibiotics produced mild but consistently higher increases in expression, that were the result of pleiotropic effects. Our findings rule out the riboswitch control of aminoglycoside resistance genes in integrons.
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Affiliation(s)
- Alberto Hipólito
- Departamento de Sanidad Animal, Facultad de Veterinaria de la Universidad Complutense de Madrid, Spain,VISAVET Health Surveillance Centre, Universidad Complutense de Madrid, Spain
| | - Lucía García-Pastor
- Departamento de Sanidad Animal, Facultad de Veterinaria de la Universidad Complutense de Madrid, Spain,VISAVET Health Surveillance Centre, Universidad Complutense de Madrid, Spain
| | | | | | - Nicolas Kieffer
- Departamento de Sanidad Animal, Facultad de Veterinaria de la Universidad Complutense de Madrid, Spain,VISAVET Health Surveillance Centre, Universidad Complutense de Madrid, Spain
| | - Ester Vergara
- Departamento de Sanidad Animal, Facultad de Veterinaria de la Universidad Complutense de Madrid, Spain,VISAVET Health Surveillance Centre, Universidad Complutense de Madrid, Spain
| | - Thomas Jové
- INSERM, CHU Limoges, RESINFIT, University of Limoges, Limoges, France
| | - Julio Álvarez
- Departamento de Sanidad Animal, Facultad de Veterinaria de la Universidad Complutense de Madrid, Spain,VISAVET Health Surveillance Centre, Universidad Complutense de Madrid, Spain
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7
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Néron B, Littner E, Haudiquet M, Perrin A, Cury J, Rocha EPC. IntegronFinder 2.0: Identification and Analysis of Integrons across Bacteria, with a Focus on Antibiotic Resistance in Klebsiella. Microorganisms 2022; 10:700. [PMID: 35456751 PMCID: PMC9024848 DOI: 10.3390/microorganisms10040700] [Citation(s) in RCA: 64] [Impact Index Per Article: 32.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2022] [Revised: 03/19/2022] [Accepted: 03/22/2022] [Indexed: 02/07/2023] Open
Abstract
Integrons are flexible gene-exchanging platforms that contain multiple cassettes encoding accessory genes whose order is shuffled by a specific integrase. Integrons embedded within mobile genetic elements often contain multiple antibiotic resistance genes that they spread among nosocomial pathogens and contribute to the current antibiotic resistance crisis. However, most integrons are presumably sedentary and encode a much broader diversity of functions. IntegronFinder is a widely used software to identify novel integrons in bacterial genomes, but has aged and lacks some useful functionalities to handle very large datasets of draft genomes or metagenomes. Here, we present IntegronFinder version 2. We have updated the code, improved its efficiency and usability, adapted the output to incomplete genome data, and added a few novel functions. We describe these changes and illustrate the relevance of the program by analyzing the distribution of integrons across more than 20,000 fully sequenced genomes. We also take full advantage of its novel capabilities to analyze close to 4000 Klebsiella pneumoniae genomes for the presence of integrons and antibiotic resistance genes within them. Our data show that K. pneumoniae has a large diversity of integrons and the largest mobile integron in our database of plasmids. The pangenome of these integrons contains a total of 165 different gene families with most of the largest families being related with resistance to numerous types of antibiotics. IntegronFinder is a free and open-source software available on multiple public platforms.
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Affiliation(s)
- Bertrand Néron
- Bioinformatics and Biostatistics Hub, Institut Pasteur, Université de Paris Cité, 75015 Paris, France; (B.N.); (A.P.)
| | - Eloi Littner
- Microbial Evolutionary Genomics, Institut Pasteur, Université de Paris Cité, CNRS UMR3525, 75015 Paris, France; (E.L.); (M.H.)
- DGA CBRN Defence, 91710 Vert-le-Petit, France
- Collège Doctoral, Sorbonne Université, 75005 Paris, France
| | - Matthieu Haudiquet
- Microbial Evolutionary Genomics, Institut Pasteur, Université de Paris Cité, CNRS UMR3525, 75015 Paris, France; (E.L.); (M.H.)
- Ecole Doctorale FIRE–Programme Bettencourt, CRI, 75004 Paris, France
| | - Amandine Perrin
- Bioinformatics and Biostatistics Hub, Institut Pasteur, Université de Paris Cité, 75015 Paris, France; (B.N.); (A.P.)
- Microbial Evolutionary Genomics, Institut Pasteur, Université de Paris Cité, CNRS UMR3525, 75015 Paris, France; (E.L.); (M.H.)
- Collège Doctoral, Sorbonne Université, 75005 Paris, France
| | - Jean Cury
- Microbial Evolutionary Genomics, Institut Pasteur, Université de Paris Cité, CNRS UMR3525, 75015 Paris, France; (E.L.); (M.H.)
- Laboratoire Interdisciplinaire des Sciences du Numérique, Université Paris-Saclay, CNRS UMR 9015, INRIA, 91400 Orsay, France
| | - Eduardo P. C. Rocha
- Microbial Evolutionary Genomics, Institut Pasteur, Université de Paris Cité, CNRS UMR3525, 75015 Paris, France; (E.L.); (M.H.)
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8
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Unbridled Integrons: A Matter of Host Factors. Cells 2022; 11:cells11060925. [PMID: 35326376 PMCID: PMC8946536 DOI: 10.3390/cells11060925] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2022] [Revised: 03/03/2022] [Accepted: 03/04/2022] [Indexed: 12/29/2022] Open
Abstract
Integrons are powerful recombination systems found in bacteria, which act as platforms capable of capturing, stockpiling, excising and reordering mobile elements called cassettes. These dynamic genetic machineries confer a very high potential of adaptation to their host and have quickly found themselves at the forefront of antibiotic resistance, allowing for the quick emergence of multi-resistant phenotypes in a wide range of bacterial species. Part of the success of the integron is explained by its ability to integrate various environmental and biological signals in order to allow the host to respond to these optimally. In this review, we highlight the substantial interconnectivity that exists between integrons and their hosts and its importance to face changing environments. We list the factors influencing the expression of the cassettes, the expression of the integrase, and the various recombination reactions catalyzed by the integrase. The combination of all these host factors allows for a very tight regulation of the system at the cost of a limited ability to spread by horizontal gene transfer and function in remotely related hosts. Hence, we underline the important consequences these factors have on the evolution of integrons. Indeed, we propose that sedentary chromosomal integrons that were less connected or connected via more universal factors are those that have been more successful upon mobilization in mobile genetic structures, in contrast to those that were connected to species-specific host factors. Thus, the level of specificity of the involved host factors network may have been decisive for the transition from chromosomal integrons to the mobile integrons, which are now widespread. As such, integrons represent a perfect example of the conflicting relationship between the ability to control a biological system and its potential for transferability.
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9
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Ghaly TM, Gillings MR, Penesyan A, Qi Q, Rajabal V, Tetu SG. The Natural History of Integrons. Microorganisms 2021; 9:2212. [PMID: 34835338 PMCID: PMC8618304 DOI: 10.3390/microorganisms9112212] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2021] [Revised: 10/22/2021] [Accepted: 10/23/2021] [Indexed: 11/17/2022] Open
Abstract
Integrons were first identified because of their central role in assembling and disseminating antibiotic resistance genes in commensal and pathogenic bacteria. However, these clinically relevant integrons represent only a small proportion of integron diversity. Integrons are now known to be ancient genetic elements that are hotspots for genomic diversity, helping to generate adaptive phenotypes. This perspective examines the diversity, functions, and activities of integrons within both natural and clinical environments. We show how the fundamental properties of integrons exquisitely pre-adapted them to respond to the selection pressures imposed by the human use of antimicrobial compounds. We then follow the extraordinary increase in abundance of one class of integrons (class 1) that has resulted from its acquisition by multiple mobile genetic elements, and subsequent colonisation of diverse bacterial species, and a wide range of animal hosts. Consequently, this class of integrons has become a significant pollutant in its own right, to the extent that it can now be detected in most ecosystems. As human activities continue to drive environmental instability, integrons will likely continue to play key roles in bacterial adaptation in both natural and clinical settings. Understanding the ecological and evolutionary dynamics of integrons can help us predict and shape these outcomes that have direct relevance to human and ecosystem health.
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Affiliation(s)
- Timothy M. Ghaly
- Department of Biological Sciences, Macquarie University, Sydney, NSW 2109, Australia; (T.M.G.); (A.P.); (Q.Q.); (V.R.)
| | - Michael R. Gillings
- Department of Biological Sciences, Macquarie University, Sydney, NSW 2109, Australia; (T.M.G.); (A.P.); (Q.Q.); (V.R.)
- ARC Centre of Excellence in Synthetic Biology, Macquarie University, Sydney, NSW 2109, Australia;
| | - Anahit Penesyan
- Department of Biological Sciences, Macquarie University, Sydney, NSW 2109, Australia; (T.M.G.); (A.P.); (Q.Q.); (V.R.)
- ARC Centre of Excellence in Synthetic Biology, Macquarie University, Sydney, NSW 2109, Australia;
- Department of Molecular Sciences, Macquarie University, Sydney, NSW 2109, Australia
| | - Qin Qi
- Department of Biological Sciences, Macquarie University, Sydney, NSW 2109, Australia; (T.M.G.); (A.P.); (Q.Q.); (V.R.)
| | - Vaheesan Rajabal
- Department of Biological Sciences, Macquarie University, Sydney, NSW 2109, Australia; (T.M.G.); (A.P.); (Q.Q.); (V.R.)
- ARC Centre of Excellence in Synthetic Biology, Macquarie University, Sydney, NSW 2109, Australia;
| | - Sasha G. Tetu
- ARC Centre of Excellence in Synthetic Biology, Macquarie University, Sydney, NSW 2109, Australia;
- Department of Molecular Sciences, Macquarie University, Sydney, NSW 2109, Australia
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10
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Predicting the taxonomic and environmental sources of integron gene cassettes using structural and sequence homology of attC sites. Commun Biol 2021; 4:946. [PMID: 34373573 PMCID: PMC8352920 DOI: 10.1038/s42003-021-02489-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2021] [Accepted: 07/16/2021] [Indexed: 11/08/2022] Open
Abstract
Integrons are bacterial genetic elements that can capture mobile gene cassettes. They are mostly known for their role in the spread of antibiotic resistance cassettes, contributing significantly to the global resistance crisis. These resistance cassettes likely originated from sedentary chromosomal integrons, having subsequently been acquired and disseminated by mobilised integrons. However, their taxonomic and environmental origins are unknown. Here, we use cassette recombination sites (attCs) to predict the origins of those resistance cassettes now spread by mobile integrons. We modelled the structure and sequence homology of 1,978 chromosomal attCs from 11 different taxa. Using these models, we show that at least 27% of resistance cassettes have attCs that are structurally conserved among one of three taxa (Xanthomonadales, Spirochaetes and Vibrionales). Indeed, we found some resistance cassettes still residing in sedentary chromosomal integrons of the predicted taxa. Further, we show that attCs cluster according to host environment rather than host phylogeny, allowing us to assign their likely environmental sources. For example, the majority of β-lactamases and aminoglycoside acetyltransferases, the two most prevalent resistance cassettes, appear to have originated from marine environments. Together, our data represent the first evidence of the taxonomic and environmental origins of resistance cassettes spread by mobile integrons.
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11
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Vit C, Richard E, Fournes F, Whiteway C, Eyer X, Lapaillerie D, Parissi V, Mazel D, Loot C. Cassette recruitment in the chromosomal Integron of Vibrio cholerae. Nucleic Acids Res 2021; 49:5654-5670. [PMID: 34048565 PMCID: PMC8191803 DOI: 10.1093/nar/gkab412] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2021] [Revised: 04/26/2021] [Accepted: 05/03/2021] [Indexed: 01/16/2023] Open
Abstract
Integrons confer a rapid adaptation capability to bacteria. Integron integrases are able to capture and shuffle novel functions embedded in cassettes. Here, we investigated cassette recruitment in the Vibrio cholerae chromosomal integron during horizontal transfer. We demonstrated that the endogenous integrase expression is sufficiently triggered, after SOS response induction mediated by the entry of cassettes during conjugation and natural transformation, to mediate significant cassette insertions. These insertions preferentially occur at the attIA site, despite the presence of about 180 attC sites in the integron array. Thanks to the presence of a promoter in the attIA site vicinity, all these newly inserted cassettes are expressed and prone to selection. We also showed that the RecA protein is critical for cassette recruitment in the V. cholerae chromosomal integron but not in mobile integrons. Moreover, unlike the mobile integron integrases, that of V. cholerae is not active in other bacteria. Mobile integrons might have evolved from the chromosomal ones by overcoming host factors, explaining their large dissemination in bacteria and their role in antibioresistance expansion.
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Affiliation(s)
- Claire Vit
- Institut Pasteur, Unité Plasticité du Génome Bactérien, CNRS UMR3525, Paris, France.,Sorbonne Université, Collège doctoral, F-75005 Paris, France
| | - Egill Richard
- Institut Pasteur, Unité Plasticité du Génome Bactérien, CNRS UMR3525, Paris, France.,Sorbonne Université, Collège doctoral, F-75005 Paris, France
| | - Florian Fournes
- Institut Pasteur, Unité Plasticité du Génome Bactérien, CNRS UMR3525, Paris, France
| | - Clémence Whiteway
- Institut Pasteur, Unité Plasticité du Génome Bactérien, CNRS UMR3525, Paris, France
| | - Xavier Eyer
- Institut Pasteur, Unité Plasticité du Génome Bactérien, CNRS UMR3525, Paris, France
| | - Delphine Lapaillerie
- CNRS, UMR5234, Fundamental Microbiology and Pathogenicity laboratory, University of Bordeaux. Département de Sciences Biologiques et Médicales, Bordeaux, France.,Viral DNA Integration and Chromatin Dynamics Network (DyNAVir), France
| | - Vincent Parissi
- CNRS, UMR5234, Fundamental Microbiology and Pathogenicity laboratory, University of Bordeaux. Département de Sciences Biologiques et Médicales, Bordeaux, France.,Viral DNA Integration and Chromatin Dynamics Network (DyNAVir), France
| | - Didier Mazel
- Institut Pasteur, Unité Plasticité du Génome Bactérien, CNRS UMR3525, Paris, France
| | - Céline Loot
- Institut Pasteur, Unité Plasticité du Génome Bactérien, CNRS UMR3525, Paris, France
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12
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Vit C, Loot C, Escudero JA, Nivina A, Mazel D. Integron Identification in Bacterial Genomes and Cassette Recombination Assays. METHODS IN MOLECULAR BIOLOGY (CLIFTON, N.J.) 2021; 2075:189-208. [PMID: 31584164 DOI: 10.1007/978-1-4939-9877-7_14] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Integrons are genetic elements involved in bacterial adaptation to the environment. Sedentary chromosomal integrons (SCIs) can stockpile and rearrange a myriad of different functions encoded in gene cassettes. Through their association with transposable elements and conjugative plasmids, some SCIs have acquired mobility and are now termed Mobile Integrons (MIs). MIs have reached the hospitals and are involved in the rise and spread of antibiotic resistance genes through horizontal gene transfer among numerous bacterial species. Here we aimed at describing methods for the detection of integrons in sequenced bacterial genomes as well as for the experimental characterization of the activity of their different components: the integrase and the recombination sites.
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Affiliation(s)
- Claire Vit
- Unité Plasticité du Génome Bactérien, Département Génomes et Génétique, Institut Pasteur, Paris, France.,CNRS, UMR3525, Paris, France.,Sorbonne Université, Collège doctoral, Paris, France
| | - Céline Loot
- Unité Plasticité du Génome Bactérien, Département Génomes et Génétique, Institut Pasteur, Paris, France.,CNRS, UMR3525, Paris, France
| | - José Antonio Escudero
- Unité Plasticité du Génome Bactérien, Département Génomes et Génétique, Institut Pasteur, Paris, France.,CNRS, UMR3525, Paris, France
| | - Aleksandra Nivina
- Unité Plasticité du Génome Bactérien, Département Génomes et Génétique, Institut Pasteur, Paris, France.,CNRS, UMR3525, Paris, France.,Paris Descartes, Sorbonne Paris Cité, Paris, France
| | - Didier Mazel
- Unité Plasticité du Génome Bactérien, Département Génomes et Génétique, Institut Pasteur, Paris, France. .,CNRS, UMR3525, Paris, France.
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13
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Escudero JA, Nivina A, Kemble HE, Loot C, Tenaillon O, Mazel D. Primary and promiscuous functions coexist during evolutionary innovation through whole protein domain acquisitions. eLife 2020; 9:58061. [PMID: 33319743 PMCID: PMC7790495 DOI: 10.7554/elife.58061] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2020] [Accepted: 12/14/2020] [Indexed: 11/13/2022] Open
Abstract
Molecular examples of evolutionary innovation are scarce and generally involve point mutations. Innovation can occur through larger rearrangements, but here experimental data is extremely limited. Integron integrases innovated from double-strand- toward single-strand-DNA recombination through the acquisition of the I2 α-helix. To investigate how this transition was possible, we have evolved integrase IntI1 to what should correspond to an early innovation state by selecting for its ancestral activity. Using synonymous alleles to enlarge sequence space exploration, we have retrieved 13 mutations affecting both I2 and the multimerization domains of IntI1. We circumvented epistasis constraints among them using a combinatorial library that revealed their individual and collective fitness effects. We obtained up to 104-fold increases in ancestral activity with various asymmetrical trade-offs in single-strand-DNA recombination. We show that high levels of primary and promiscuous functions could have initially coexisted following I2 acquisition, paving the way for a gradual evolution toward innovation.
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Affiliation(s)
- José Antonio Escudero
- Institut Pasteur, Unité de Plasticité du Génome Bactérien, Département Génomes et Génétique, Paris, France.,CNRS, UMR3525, Paris, France.,Molecular Basis of Adaptation, Departamento de Sanidad Animal, Facultad de Veterinaria, Universidad Complutense de Madrid, Madrid, Spain.,VISAVET Health Surveillance Centre. Universidad Complutense Madrid. Avenida Puerta de Hierro, Madrid, Spain
| | - Aleksandra Nivina
- Institut Pasteur, Unité de Plasticité du Génome Bactérien, Département Génomes et Génétique, Paris, France.,CNRS, UMR3525, Paris, France.,Université Paris Descartes, Sorbonne Paris Cité, Paris, France
| | - Harry E Kemble
- Infection, Antimicrobials, Modelling, Evolution, INSERM, UMR 1137, Université Paris Diderot, Université Paris Nord, Paris, France
| | - Céline Loot
- Institut Pasteur, Unité de Plasticité du Génome Bactérien, Département Génomes et Génétique, Paris, France.,CNRS, UMR3525, Paris, France
| | - Olivier Tenaillon
- Infection, Antimicrobials, Modelling, Evolution, INSERM, UMR 1137, Université Paris Diderot, Université Paris Nord, Paris, France
| | - Didier Mazel
- Institut Pasteur, Unité de Plasticité du Génome Bactérien, Département Génomes et Génétique, Paris, France.,CNRS, UMR3525, Paris, France
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14
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Nivina A, Grieb MS, Loot C, Bikard D, Cury J, Shehata L, Bernardes J, Mazel D. Structure-specific DNA recombination sites: Design, validation, and machine learning-based refinement. SCIENCE ADVANCES 2020; 6:eaay2922. [PMID: 32832653 PMCID: PMC7439510 DOI: 10.1126/sciadv.aay2922] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/04/2019] [Accepted: 06/12/2020] [Indexed: 06/11/2023]
Abstract
Recombination systems are widely used as bioengineering tools, but their sites have to be highly similar to a consensus sequence or to each other. To develop a recombination system free of these constraints, we turned toward attC sites from the bacterial integron system: single-stranded DNA hairpins specifically recombined by the integrase. Here, we present an algorithm that generates synthetic attC sites with conserved structural features and minimal sequence-level constraints. We demonstrate that all generated sites are functional, their recombination efficiency can reach 60%, and they can be embedded into protein coding sequences. To improve recombination of less efficient sites, we applied large-scale mutagenesis and library enrichment coupled to next-generation sequencing and machine learning. Our results validated the efficiency of this approach and allowed us to refine synthetic attC design principles. They can be embedded into virtually any sequence and constitute a unique example of a structure-specific DNA recombination system.
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Affiliation(s)
- Aleksandra Nivina
- Unité Plasticité du Génome Bactérien, Institut Pasteur, 75724 Paris, France
- CNRS UMR 3525, 75724 Paris, France
- Paris Descartes, Sorbonne Paris Cité, Paris, France
| | - Maj Svea Grieb
- Unité Plasticité du Génome Bactérien, Institut Pasteur, 75724 Paris, France
- CNRS UMR 3525, 75724 Paris, France
| | - Céline Loot
- Unité Plasticité du Génome Bactérien, Institut Pasteur, 75724 Paris, France
- CNRS UMR 3525, 75724 Paris, France
| | - David Bikard
- Unité Plasticité du Génome Bactérien, Institut Pasteur, 75724 Paris, France
- CNRS UMR 3525, 75724 Paris, France
| | - Jean Cury
- Unité Plasticité du Génome Bactérien, Institut Pasteur, 75724 Paris, France
- CNRS UMR 3525, 75724 Paris, France
- Paris Descartes, Sorbonne Paris Cité, Paris, France
| | - Laila Shehata
- Unité Plasticité du Génome Bactérien, Institut Pasteur, 75724 Paris, France
- CNRS UMR 3525, 75724 Paris, France
| | - Juliana Bernardes
- Laboratoire de Biologie Computationnelle et Quantitative, Sorbonne Universités, CNRS UMR 7238,75005 Paris, France
| | - Didier Mazel
- Unité Plasticité du Génome Bactérien, Institut Pasteur, 75724 Paris, France
- CNRS UMR 3525, 75724 Paris, France
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15
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Das B, Verma J, Kumar P, Ghosh A, Ramamurthy T. Antibiotic resistance in Vibrio cholerae: Understanding the ecology of resistance genes and mechanisms. Vaccine 2020; 38 Suppl 1:A83-A92. [DOI: 10.1016/j.vaccine.2019.06.031] [Citation(s) in RCA: 66] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2019] [Revised: 04/11/2019] [Accepted: 06/04/2019] [Indexed: 11/29/2022]
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16
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Mukhortava A, Pöge M, Grieb MS, Nivina A, Loot C, Mazel D, Schlierf M. Structural heterogeneity of attC integron recombination sites revealed by optical tweezers. Nucleic Acids Res 2019; 47:1861-1870. [PMID: 30566629 PMCID: PMC6393395 DOI: 10.1093/nar/gky1258] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2018] [Revised: 12/02/2018] [Accepted: 12/04/2018] [Indexed: 11/12/2022] Open
Abstract
A predominant tool for adaptation in Gram-negative bacteria is the functional genetic platform called integron. Integrons capture and rearrange promoterless gene cassettes in a unique recombination process involving the recognition of folded single-stranded DNA hairpins—so-called attC sites—with a strong preference for the attC bottom strand. While structural elements have been identified to promote this preference, their mechanistic action remains incomplete. Here, we used high-resolution single-molecule optical tweezers (OT) to characterize secondary structures formed by the attC bottom (\documentclass[12pt]{minimal}
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}{}${{att}}{{{C}}_{{\rm{bs}}}}$\end{document}) and top (\documentclass[12pt]{minimal}
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}{}${{att}}{{{C}}_{{\rm{ts}}}}$\end{document}) strands of the paradigmatic attCaadA7 site. We found for both sequences two structures—a straight, canonical hairpin and a kinked hairpin. Remarkably, the recombination-preferred \documentclass[12pt]{minimal}
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}{}${{att}}{{{C}}_{{\rm{bs}}}}$\end{document} predominantly formed the straight hairpin, while the \documentclass[12pt]{minimal}
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}{}${{att}}{{{C}}_{{\rm{ts}}}}$\end{document} preferentially adopted the kinked structure, which exposes only one complete recombinase binding box. By a mutational analysis, we identified three bases in the unpaired central spacer, which could invert the preferred conformations and increase the recombination frequency of the \documentclass[12pt]{minimal}
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}{}${{att}}{{{C}}_{{\rm{ts}}}}$\end{document}in vivo. A bioinformatics screen revealed structural bias toward a straight, canonical hairpin conformation in the bottom strand of many antibiotic resistance cassettes attC sites. Thus, we anticipate that structural fine tuning could be a mechanism in many biologically active DNA hairpins.
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Affiliation(s)
- Ann Mukhortava
- B CUBE - Center for Molecular Bioengineering, TU Dresden, Tatzberg 41, 01307 Dresden, Germany
| | - Matthias Pöge
- B CUBE - Center for Molecular Bioengineering, TU Dresden, Tatzberg 41, 01307 Dresden, Germany
| | - Maj Svea Grieb
- B CUBE - Center for Molecular Bioengineering, TU Dresden, Tatzberg 41, 01307 Dresden, Germany
| | - Aleksandra Nivina
- Institut Pasteur, Unité de Plasticité du Génome Bactérien, Département Génomes et Génétique, 28 Rue du Dr Roux, 75015 Paris, France.,CNRS, UMR3525, 28 Rue du Dr Roux, 75015 Paris, France.,Paris Descartes University, 75006 Paris, France
| | - Celine Loot
- Institut Pasteur, Unité de Plasticité du Génome Bactérien, Département Génomes et Génétique, 28 Rue du Dr Roux, 75015 Paris, France.,CNRS, UMR3525, 28 Rue du Dr Roux, 75015 Paris, France
| | - Didier Mazel
- Institut Pasteur, Unité de Plasticité du Génome Bactérien, Département Génomes et Génétique, 28 Rue du Dr Roux, 75015 Paris, France.,CNRS, UMR3525, 28 Rue du Dr Roux, 75015 Paris, France
| | - Michael Schlierf
- B CUBE - Center for Molecular Bioengineering, TU Dresden, Tatzberg 41, 01307 Dresden, Germany
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17
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Engineered toxin–intein antimicrobials can selectively target and kill antibiotic-resistant bacteria in mixed populations. Nat Biotechnol 2019; 37:755-760. [DOI: 10.1038/s41587-019-0105-3] [Citation(s) in RCA: 70] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2018] [Accepted: 03/13/2019] [Indexed: 01/21/2023]
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18
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Escudero JA, Nivina A, Cambray G, López-Igual R, Loot C, Mazel D. Recoding of synonymous genes to expand evolutionary landscapes requires control of secondary structure affecting translation. Biotechnol Bioeng 2018; 115:184-191. [DOI: 10.1002/bit.26450] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2017] [Revised: 08/23/2017] [Accepted: 09/08/2017] [Indexed: 11/08/2022]
Affiliation(s)
- Jose A. Escudero
- Institut Pasteur; Unité de Plasticité du Génome Bactérien; Département Génomes et Génétique; Paris France
- CNRS; UMR3525; Paris France
- Departamento de Sanidad Animal; Facultad de Veterinaria; Universidad Complutense de Madrid; Madrid Spain
- VISAVET Health Surveillance Centre; Universidad Complutense Madrid; Madrid Spain
| | - Aleksandra Nivina
- Institut Pasteur; Unité de Plasticité du Génome Bactérien; Département Génomes et Génétique; Paris France
- CNRS; UMR3525; Paris France
- Université Paris Descartes; Sorbonne Paris Cité; Paris France
| | | | - Rocío López-Igual
- Institut Pasteur; Unité de Plasticité du Génome Bactérien; Département Génomes et Génétique; Paris France
- CNRS; UMR3525; Paris France
| | - Celine Loot
- Institut Pasteur; Unité de Plasticité du Génome Bactérien; Département Génomes et Génétique; Paris France
- CNRS; UMR3525; Paris France
| | - Didier Mazel
- Institut Pasteur; Unité de Plasticité du Génome Bactérien; Département Génomes et Génétique; Paris France
- CNRS; UMR3525; Paris France
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19
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Grieb MS, Nivina A, Cheeseman BL, Hartmann A, Mazel D, Schlierf M. Dynamic stepwise opening of integron attC DNA hairpins by SSB prevents toxicity and ensures functionality. Nucleic Acids Res 2017; 45:10555-10563. [PMID: 28985409 PMCID: PMC5737091 DOI: 10.1093/nar/gkx670] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2017] [Accepted: 07/22/2017] [Indexed: 11/22/2022] Open
Abstract
Biologically functional DNA hairpins are found in archaea, prokaryotes and eukaryotes, playing essential roles in various DNA transactions. However, during DNA replication, hairpin formation can stall the polymerase and is therefore prevented by the single-stranded DNA binding protein (SSB). Here, we address the question how hairpins maintain their functional secondary structure despite SSB’s presence. As a model hairpin, we used the recombinogenic form of the attC site, essential for capturing antibiotic-resistance genes in the integrons of bacteria. We found that attC hairpins have a conserved high GC-content near their apical loop that creates a dynamic equilibrium between attC fully opened by SSB and a partially structured attC-6–SSB complex. This complex is recognized by the recombinase IntI, which extrudes the hairpin upon binding while displacing SSB. We anticipate that this intriguing regulation mechanism using a base pair distribution to balance hairpin structure formation and genetic stability is key to the dissemination of antibiotic resistance genes among bacteria and might be conserved among other functional hairpins.
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Affiliation(s)
- Maj Svea Grieb
- B CUBE - Center for Molecular Bioengineering, Technische Universität Dresden, Arnoldstraße 18, 01307 Dresden, Germany
| | - Aleksandra Nivina
- Institut Pasteur, Unité Plasticité du Génome Bactérien, Département Génomes et Génétique, 28 rue du Dr. Roux, 75724 Paris, France.,CNRS UMR3525, 75724 Paris, France.,Paris Descartes University, 75006 Paris, France
| | - Bevan L Cheeseman
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstr. 108, 01307 Dresden, Germany
| | - Andreas Hartmann
- B CUBE - Center for Molecular Bioengineering, Technische Universität Dresden, Arnoldstraße 18, 01307 Dresden, Germany
| | - Didier Mazel
- Institut Pasteur, Unité Plasticité du Génome Bactérien, Département Génomes et Génétique, 28 rue du Dr. Roux, 75724 Paris, France.,CNRS UMR3525, 75724 Paris, France
| | - Michael Schlierf
- B CUBE - Center for Molecular Bioengineering, Technische Universität Dresden, Arnoldstraße 18, 01307 Dresden, Germany
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20
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Gillings MR. Class 1 integrons as invasive species. Curr Opin Microbiol 2017; 38:10-15. [DOI: 10.1016/j.mib.2017.03.002] [Citation(s) in RCA: 72] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2017] [Revised: 03/02/2017] [Accepted: 03/07/2017] [Indexed: 02/05/2023]
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21
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Bland MJ, Ducos-Galand M, Val ME, Mazel D. An att site-based recombination reporter system for genome engineering and synthetic DNA assembly. BMC Biotechnol 2017; 17:62. [PMID: 28705159 PMCID: PMC5512741 DOI: 10.1186/s12896-017-0382-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2017] [Accepted: 07/09/2017] [Indexed: 11/25/2022] Open
Abstract
Background Direct manipulation of the genome is a widespread technique for genetic studies and synthetic biology applications. The tyrosine and serine site-specific recombination systems of bacteriophages HK022 and ΦC31 are widely used for stable directional exchange and relocation of DNA sequences, making them valuable tools in these contexts. We have developed site-specific recombination tools that allow the direct selection of recombination events by embedding the attB site from each system within the β-lactamase resistance coding sequence (bla). Results The HK and ΦC31 tools were developed by placing the attB sites from each system into the signal peptide cleavage site coding sequence of bla. All possible open reading frames (ORFs) were inserted and tested for recombination efficiency and bla activity. Efficient recombination was observed for all tested ORFs (3 for HK, 6 for ΦC31) as shown through a cointegrate formation assay. The bla gene with the embedded attB site was functional for eight of the nine constructs tested. Conclusions The HK/ΦC31 att-bla system offers a simple way to directly select recombination events, thus enhancing the use of site-specific recombination systems for carrying out precise, large-scale DNA manipulation, and adding useful tools to the genetics toolbox. We further show the power and flexibility of bla to be used as a reporter for recombination.
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Affiliation(s)
- Michael J Bland
- Unité Plasticité du Génome Bactérien, Département Génomes et Génétique, Institut Pasteur, 75015, Paris, France.,UMR3525, Centre National de la Recherche Scientifique, 75015, Paris, France
| | - Magaly Ducos-Galand
- Unité Plasticité du Génome Bactérien, Département Génomes et Génétique, Institut Pasteur, 75015, Paris, France.,UMR3525, Centre National de la Recherche Scientifique, 75015, Paris, France
| | - Marie-Eve Val
- Unité Plasticité du Génome Bactérien, Département Génomes et Génétique, Institut Pasteur, 75015, Paris, France.,UMR3525, Centre National de la Recherche Scientifique, 75015, Paris, France
| | - Didier Mazel
- Unité Plasticité du Génome Bactérien, Département Génomes et Génétique, Institut Pasteur, 75015, Paris, France. .,UMR3525, Centre National de la Recherche Scientifique, 75015, Paris, France.
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22
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Gillings MR, Paulsen IT, Tetu SG. Genomics and the evolution of antibiotic resistance. Ann N Y Acad Sci 2016; 1388:92-107. [DOI: 10.1111/nyas.13268] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2016] [Accepted: 09/06/2016] [Indexed: 12/21/2022]
Affiliation(s)
| | - Ian T. Paulsen
- Department of Chemistry and Biomolecular Sciences; Macquarie University; Sydney Australia
| | - Sasha G. Tetu
- Department of Chemistry and Biomolecular Sciences; Macquarie University; Sydney Australia
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23
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Gillings MR. Lateral gene transfer, bacterial genome evolution, and the Anthropocene. Ann N Y Acad Sci 2016; 1389:20-36. [DOI: 10.1111/nyas.13213] [Citation(s) in RCA: 82] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2016] [Revised: 07/20/2016] [Accepted: 07/28/2016] [Indexed: 11/26/2022]
Affiliation(s)
- Michael R. Gillings
- Genes to Geoscience Research Centre, Department of Biological Sciences Macquarie University Sydney New South Wales Australia
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24
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Abstract
The integron is a powerful system which, by capturing, stockpiling, and rearranging new functions carried by gene encoding cassettes, confers upon bacteria a rapid adaptation capability in changing environments. Chromosomally located integrons (CI) have been identified in a large number of environmental Gram-negative bacteria. Integron evolutionary history suggests that these sedentary CIs acquired mobility among bacterial species through their association with transposable elements and conjugative plasmids. As a result of massive antibiotic use, these so-called mobile integrons are now widespread in clinically relevant bacteria and are considered to be the principal agent in the emergence and rise of antibiotic multiresistance in Gram-negative bacteria. Cassette rearrangements are catalyzed by the integron integrase, a site-specific tyrosine recombinase. Central to these reactions is the single-stranded DNA nature of one of the recombination partners, the attC site. This makes the integron a unique recombination system. This review describes the current knowledge on this atypical recombination mechanism, its implications in the reactions involving the different types of sites, attC and attI, and focuses on the tight regulation exerted by the host on integron activity through the control of attC site folding. Furthermore, cassette and integrase expression are also highly controlled by host regulatory networks and the bacterial stress (SOS) response. These intimate connections to the host make the integron a genetically stable and efficient system, granting the bacteria a low cost, highly adaptive evolution potential "on demand".
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Unmasking the ancestral activity of integron integrases reveals a smooth evolutionary transition during functional innovation. Nat Commun 2016; 7:10937. [PMID: 26961432 PMCID: PMC4792948 DOI: 10.1038/ncomms10937] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2015] [Accepted: 02/03/2016] [Indexed: 12/28/2022] Open
Abstract
Tyrosine (Y)-recombinases have evolved to deliver mechanistically different reactions on a variety of substrates, but these evolutionary transitions are poorly understood. Among them, integron integrases are hybrid systems recombining single- and double-stranded DNA partners. These reactions are asymmetric and need a replicative resolution pathway, an exception to the canonical second strand exchange model of Y-recombinases. Integron integrases possess a specific domain for this specialized pathway. Here we show that despite this, integrases are still capable of efficiently operating the ancestral second strand exchange in symmetrical reactions between double-stranded substrates. During these reactions, both strands are reactive and Holliday junction resolution can follow either pathway. A novel deep-sequencing approach allows mapping of the crossover point for the second strand exchange. The persistence of the ancestral activity in integrases illustrates their robustness and shows that innovation towards new recombination substrates and resolution pathways was a smooth evolutionary process. The integron integrases have evolved to perform recombination of single and double stranded DNA. Here the authors show that the ancestral pathway is still functional at double stranded sites, revealing the evolution towards the modern resolution pathway.
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Oliveira-Pinto C, Costa PS, Reis MP, Chartone-Souza E, Nascimento AMA. Diversity of gene cassettes and the abundance of the class 1 integron-integrase gene in sediment polluted by metals. Extremophiles 2016; 20:283-9. [PMID: 26961777 DOI: 10.1007/s00792-016-0820-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2015] [Accepted: 02/23/2016] [Indexed: 11/25/2022]
Abstract
The integron-gene cassette system has typically been associated with antibiotic-resistant pathogens. However, the diversity of gene cassettes and the abundance of class 1 integrons outside of the clinical context are not fully explored. Primers targeting the conserved segments of attC recombination sites were used to amplify gene cassettes from the sediment of the Mina stream, which exhibited a higher degree of stress to metal pollution in the dry season than the rainy season. Of the 143 total analyzed sequences, 101 had no matches to proteins in the database, where cassette open reading frames could be identified by homology with database entries. There was a predominance of sequences encoding essential cellular functions. Each season that was sampled yielded a specific pool of gene cassettes. Real-time PCR revealed that 8.5 and 41.6 % of bacterial cells potentially harbored a class 1 integron in the rainy and dry seasons, respectively. In summary, our findings demonstrate that most of the gene cassettes have no ascribable function and, apparently, historically metal-contaminated sediment favors the maintenance of bacteria containing the intI1 gene. Thus, the diversity of gene cassettes is far from being fully explored deserving further attention.
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Affiliation(s)
- Clarisse Oliveira-Pinto
- Departamento de Biologia Geral, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Av. Antônio Carlos 6627, Belo Horizonte, Minas Gerais, 31270-901, Brazil
| | - Patrícia S Costa
- Departamento de Biologia Geral, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Av. Antônio Carlos 6627, Belo Horizonte, Minas Gerais, 31270-901, Brazil
| | - Mariana P Reis
- Departamento de Biologia Geral, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Av. Antônio Carlos 6627, Belo Horizonte, Minas Gerais, 31270-901, Brazil
| | - Edmar Chartone-Souza
- Departamento de Biologia Geral, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Av. Antônio Carlos 6627, Belo Horizonte, Minas Gerais, 31270-901, Brazil
| | - Andréa M A Nascimento
- Departamento de Biologia Geral, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Av. Antônio Carlos 6627, Belo Horizonte, Minas Gerais, 31270-901, Brazil.
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27
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Abstract
Integrons are versatile gene acquisition systems commonly found in bacterial genomes. They are ancient elements that are a hot spot for genomic complexity, generating phenotypic diversity and shaping adaptive responses. In recent times, they have had a major role in the acquisition, expression, and dissemination of antibiotic resistance genes. Assessing the ongoing threats posed by integrons requires an understanding of their origins and evolutionary history. This review examines the functions and activities of integrons before the antibiotic era. It shows how antibiotic use selected particular integrons from among the environmental pool of these elements, such that integrons carrying resistance genes are now present in the majority of Gram-negative pathogens. Finally, it examines the potential consequences of widespread pollution with the novel integrons that have been assembled via the agency of human antibiotic use and speculates on the potential uses of integrons as platforms for biotechnology.
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Gillings MR, Gaze WH, Pruden A, Smalla K, Tiedje JM, Zhu YG. Using the class 1 integron-integrase gene as a proxy for anthropogenic pollution. ISME JOURNAL 2014; 9:1269-79. [PMID: 25500508 PMCID: PMC4438328 DOI: 10.1038/ismej.2014.226] [Citation(s) in RCA: 825] [Impact Index Per Article: 82.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/13/2014] [Revised: 09/18/2014] [Accepted: 10/23/2014] [Indexed: 12/14/2022]
Abstract
Around all human activity, there are zones of pollution with pesticides, heavy metals, pharmaceuticals, personal care products and the microorganisms associated with human waste streams and agriculture. This diversity of pollutants, whose concentration varies spatially and temporally, is a major challenge for monitoring. Here, we suggest that the relative abundance of the clinical class 1 integron-integrase gene, intI1, is a good proxy for pollution because: (1) intI1 is linked to genes conferring resistance to antibiotics, disinfectants and heavy metals; (2) it is found in a wide variety of pathogenic and nonpathogenic bacteria; (3) its abundance can change rapidly because its host cells can have rapid generation times and it can move between bacteria by horizontal gene transfer; and (4) a single DNA sequence variant of intI1 is now found on a wide diversity of xenogenetic elements, these being complex mosaic DNA elements fixed through the agency of human selection. Here we review the literature examining the relationship between anthropogenic impacts and the abundance of intI1, and outline an approach by which intI1 could serve as a proxy for anthropogenic pollution.
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Affiliation(s)
- Michael R Gillings
- Department of Biological Sciences, Genes to Geoscience Research Centre, Macquarie University, Sydney, New South Wales, Australia
| | - William H Gaze
- European Centre for Environment and Human Health, University of Exeter Medical School, Royal Cornwall Hospital, Truro, UK
| | - Amy Pruden
- Via Department of Civil and Environmental Engineering, Virginia Tech, Blacksburg, VA, USA
| | - Kornelia Smalla
- Institute for Epidemiology and Pathogen Diagnostics, Julius Kühn-Institut, Federal Research Centre for Cultivated Plants, Braunschweig, Germany
| | - James M Tiedje
- Center for Microbial Ecology, Michigan State University, East Lansing, MI, USA
| | - Yong-Guan Zhu
- Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen, China
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29
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López-Pérez M, Gonzaga A, Ivanova EP, Rodriguez-Valera F. Genomes of Alteromonas australica, a world apart. BMC Genomics 2014; 15:483. [PMID: 24942065 PMCID: PMC4119200 DOI: 10.1186/1471-2164-15-483] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2014] [Accepted: 06/13/2014] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Alteromonas is a genus of marine bacteria that is very easy to isolate and grow in the laboratory. There are genomes available of the species Alteromonas macleodii from different locations around the world and an Alteromonas sp. isolated from a sediment in Korea. We have analyzed the genomes of two strains classified by 16S rRNA (>99% similarity) as the recently described species Alteromonas australica, and isolated from opposite ends of the world; A. australica DE170 was isolated in the South Adriatic (Mediterranean) at 1000 m depth while A. australica H17T was isolated from a sea water sample collected in St Kilda Beach, Tasman Sea. RESULTS Although these two strains belong to a clearly different species from A. macleodii, the overall synteny is well preserved and the flexible genomic islands seem to code for equivalent functions and be located at similar positions. Actually the genomes of all the Alteromonas species known to date seem to preserve synteny quite well with the only exception of the sediment isolate SN2. Among the specific metabolic features found for the A. australica isolates there is the degradation of xylan and production of cellulose as extracellular polymeric substance by DE170 or the potential ethanol/methanol degradation by H17T. CONCLUSIONS The genomes of the two A. australica isolates are not more different than those of strains of A. macleodii isolated from the same sample. Actually the recruitment from metagenomes indicates that all the available genomes are found in most tropical-temperate marine samples analyzed and that they live in consortia of several species and multiple clones within each. Overall the hydrolytic activities of the Alteromonas genus as a whole are impressive and fit with its known capabilities to exploit sudden inputs of organic matter in their environment.
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Affiliation(s)
| | | | | | - Francisco Rodriguez-Valera
- División de Microbiología, Evolutionary Genomics Group, Universidad Miguel Hernández, Apartado 18, San Juan, 03550 Alicante, Spain.
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Krin E, Cambray G, Mazel D. The superintegron integrase and the cassette promoters are co-regulated in Vibrio cholerae. PLoS One 2014; 9:e91194. [PMID: 24614503 PMCID: PMC3948777 DOI: 10.1371/journal.pone.0091194] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2013] [Accepted: 02/10/2014] [Indexed: 12/23/2022] Open
Abstract
Chromosome 2 of Vibrio cholerae carries a chromosomal superintegron, composed of an integrase, a cassette integration site (attI) and an array of mostly promoterless gene cassettes. We determined the precise location of the promoter, Pc, which drives the transcription of the first cassettes of the V. cholerae superintegron. We found that cassette mRNA starts 65 bp upstream of the attI site, so that the inversely oriented promoters Pc and Pint (integrase promoter) partly overlap, allowing for their potential co-regulation. Pint was previously shown to be induced during the SOS response and is further controlled by the catabolite repression cAMP-CRP complex. We found that cassette expression from Pc was also controlled by the cAMP-CRP complex, but is not part of the SOS regulon. Pint and Pc promoters were both found to be induced in rich medium, at high temperature, high salinity and at the end of exponential growth phase, although at very different levels and independently of sigma factor RpoS. All these results show that expression from the integrase and cassette promoters can take place at the same time, thus leading to coordinated excisions and integrations within the superintegron and potentially coupling cassette shuffling to immediate selective advantage.
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Affiliation(s)
- Evelyne Krin
- Institut Pasteur, Unité de Plasticité du Génome Bactérien, Département Génomes et Génétique, Paris, France
- CNRS, UMR 3525, Paris, France
| | - Guillaume Cambray
- Institut Pasteur, Unité de Plasticité du Génome Bactérien, Département Génomes et Génétique, Paris, France
| | - Didier Mazel
- Institut Pasteur, Unité de Plasticité du Génome Bactérien, Département Génomes et Génétique, Paris, France
- CNRS, UMR 3525, Paris, France
- * E-mail:
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31
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Rapa RA, Labbate M. The function of integron-associated gene cassettes in Vibrio species: the tip of the iceberg. Front Microbiol 2013; 4:385. [PMID: 24367362 PMCID: PMC3856429 DOI: 10.3389/fmicb.2013.00385] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2013] [Accepted: 11/25/2013] [Indexed: 12/17/2022] Open
Abstract
The integron is a genetic element that incorporates mobile genes termed gene cassettes into a reserved genetic site via site-specific recombination. It is best known for its role in antibiotic resistance with one type of integron, the class 1 integron, a major player in the dissemination of antibiotic resistance genes across Gram negative pathogens and commensals. However, integrons are ancient structures with over 100 classes (including class 1) present in bacteria from the broader environment. While, the class 1 integron is only one example of an integron being mobilized into the clinical environment, it is by far the most successful. Unlike clinical class 1 integrons which are largely found on plasmids, other integron classes are found on the chromosomes of bacteria and carry diverse gene cassettes indicating a non-antibiotic resistance role(s). However, there is very limited knowledge on what these alternative roles are. This is particularly relevant to Vibrio species where gene cassettes make up approximately 1-3% of their entire genome. In this review, we discuss how emphasis on class 1 integron research has resulted in a limited understanding by the wider research community on the role of integrons in the broader environment. This has the capacity to be counterproductive in solving or improving the antibiotic resistance problem into the future. Furthermore, there is still a significant lack of knowledge on how gene cassettes in Vibrio species drive adaptation and evolution. From research in Vibrio rotiferianus DAT722, new insight into how gene cassettes affect cellular physiology offers new alternative roles for the gene cassette resource. At least a subset of gene cassettes are involved in host surface polysaccharide modification suggesting that gene cassettes may be important in processes such as bacteriophage resistance, adhesion/biofilm formation, protection from grazers and bacterial aggregation.
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Affiliation(s)
- Rita A Rapa
- ithree Institute, University of Technology Sydney, NSW, Australia ; Department of Medical and Molecular Biosciences, University of Technology Sydney, NSW, Australia
| | - Maurizio Labbate
- ithree Institute, University of Technology Sydney, NSW, Australia ; Department of Medical and Molecular Biosciences, University of Technology Sydney, NSW, Australia
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32
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Multiple Pathways of Genome Plasticity Leading to Development of Antibiotic Resistance. Antibiotics (Basel) 2013; 2:288-315. [PMID: 27029305 PMCID: PMC4790341 DOI: 10.3390/antibiotics2020288] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2013] [Revised: 05/21/2013] [Accepted: 05/23/2013] [Indexed: 02/05/2023] Open
Abstract
The emergence of multi-resistant bacterial strains is a major source of concern and has been correlated with the widespread use of antibiotics. The origins of resistance are intensively studied and many mechanisms involved in resistance have been identified, such as exogenous gene acquisition by horizontal gene transfer (HGT), mutations in the targeted functions, and more recently, antibiotic tolerance through persistence. In this review, we focus on factors leading to integron rearrangements and gene capture facilitating antibiotic resistance acquisition, maintenance and spread. The role of stress responses, such as the SOS response, is discussed.
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Loot C, Ducos-Galand M, Escudero JA, Bouvier M, Mazel D. Replicative resolution of integron cassette insertion. Nucleic Acids Res 2012; 40:8361-70. [PMID: 22740653 PMCID: PMC3458562 DOI: 10.1093/nar/gks620] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Site-specific recombination catalyzed by tyrosine recombinases follows a common pathway consisting of two consecutive strand exchanges. The first strand exchange generates a Holliday junction (HJ), which is resolved by a second strand exchange. In integrons, attC sites recombine as folded single-stranded substrates. Only one of the two attC site strands, the bottom one, is efficiently bound and cleaved by the integrase during the insertion of gene cassettes at the double-stranded attI site. Due to the asymmetry of this complex, a second strand exchange on the attC bottom strand (bs) would form linearized abortive recombination products. We had proposed that HJ resolution would rely on an uncharacterized mechanism, probably replication. Using an attC site carried on a plasmid with each strand specifically tagged, we followed the destiny of each strand after recombination. We demonstrated that only one strand, the one carrying the attC bs, is exchanged. Furthermore, we show that the recombination products contain the attC site bs and its entire de novo synthesized complementary strand. Therefore, we demonstrate the replicative resolution of single-strand recombination in integrons and rule out the involvement of a second strand exchange of any kind in the attC × attI reaction.
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Affiliation(s)
- Céline Loot
- Institut Pasteur, Unité Plasticité du Génome Bactérien, CNRS UMR3525, Paris 75724, France
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Connecting environment and genome plasticity in the characterization of transformation-induced SOS regulation and carbon catabolite control of the Vibrio cholerae integron integrase. J Bacteriol 2012; 194:1659-67. [PMID: 22287520 DOI: 10.1128/jb.05982-11] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The human pathogen Vibrio cholerae carries a chromosomal superintegron (SI). The SI contains an array of hundreds of gene cassettes organized in tandem which are stable under conditions when no particular stress is applied to bacteria (such as during laboratory growth). Rearrangements of these cassettes are catalyzed by the activity of the associated integron integrase. Understanding the regulation of integrase expression is pivotal to fully comprehending the role played by this genetic reservoir for bacterial adaptation and its connection with the development of antibiotic resistance. Our previous work established that the integrase is regulated by the bacterial SOS response and that it is induced during bacterial conjugation. Here, we show that transformation, another horizontal gene transfer (HGT) mechanism, also triggers integrase expression through SOS induction, underlining the importance of HGT in genome plasticity. Moreover, we report a new cyclic AMP (cAMP)-cAMP receptor protein (CRP)-dependent regulation mechanism of the integrase, highlighting the influence of the extracellular environment on chromosomal gene content. Altogether, our data suggest an interplay between different stress responses and regulatory pathways for the modulation of the recombinase expression, thus showing how the SI remodeling mechanism is merged into bacterial physiology.
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35
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Gestal AM, Liew EF, Coleman NV. Natural transformation with synthetic gene cassettes: new tools for integron research and biotechnology. Microbiology (Reading) 2011; 157:3349-3360. [DOI: 10.1099/mic.0.051623-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Integrons are genetic elements that can capture and express genes packaged as gene cassettes. Here we report new methods that allow integrons to be studied and manipulated in their native bacterial hosts. Synthetic gene cassettes encoding gentamicin resistance (aadB) and green fluorescence (gfp), or lactose metabolism (lacZY), were made by PCR and self-ligation, converted to large tandem arrays by multiple displacement amplification, and introduced into Escherichia coli or Pseudomonas stutzeri strains via electroporation or natural transformation. Recombinants (GmR or Lac+) were obtained at frequencies ranging from 101 to 106 c.f.u. (µg DNA)−1. Cassettes were integrated by site-specific recombination at the integron attI site in nearly all cases examined (370/384), including both promoterless and promoter-containing cassettes. Fluorometric analysis of gfp-containing recombinants revealed that expression levels from the integron-associated promoter PC were five- to 10-fold higher in the plasmid-borne integron In3 compared with the P. stutzeri chromosomal integrons. Integration of lacZY cassettes into P. stutzeri integrons allowed the bacteria to grow on lactose, and the lacZY gene cassette was stably maintained in the absence of selection. This study is believed to be the first to show natural transformation by gene cassettes, and integron-mediated capture of catabolic gene cassettes.
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Affiliation(s)
- Alicia M. Gestal
- School of Molecular Bioscience, Building G08, The University of Sydney, NSW 2006, Australia
| | - Elissa F. Liew
- School of Molecular Bioscience, Building G08, The University of Sydney, NSW 2006, Australia
| | - Nicholas V. Coleman
- School of Molecular Bioscience, Building G08, The University of Sydney, NSW 2006, Australia
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Ke X, Gu B, Pan S, Tong M. Epidemiology and molecular mechanism of integron-mediated antibiotic resistance in Shigella. Arch Microbiol 2011; 193:767-74. [PMID: 21842348 DOI: 10.1007/s00203-011-0744-3] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2011] [Revised: 07/27/2011] [Accepted: 08/02/2011] [Indexed: 01/15/2023]
Abstract
Integrons are gene capture and expression systems that are characterized by the presence of an integrase gene. This encodes an integrase, a recombined site, and a promoter. They are able to capture gene cassettes from the environment and incorporate them using site-specific recombination. The role of integrons and gene cassettes in the dissemination of multidrug resistance in Gram-negative bacteria is significant. In Shigella species, antimicrobial resistance is often associated with the presence of class 1 and class 2 integrons that contain resistance gene cassettes. Multiple and complex expression regulation mechanisms involving mobile genetic elements in integrons have been developed in the evolution of Shigella strains. Knowledge of the epidemiology and molecular mechanisms of antimicrobial resistance in this important pathogen is essential for the implementation of intervention strategies. This review was conducted to introduce the structures and functions of integrons in Shigella species and mechanisms that control integron-mediated events linked to antibiotic resistance.
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Affiliation(s)
- Xing Ke
- Department of Laboratory Medicine, The First Affiliated Hospital of Nanjing Medical University, Nanjing 210029, China
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37
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Stokes HW, Gillings MR. Gene flow, mobile genetic elements and the recruitment of antibiotic resistance genes into Gram-negative pathogens. FEMS Microbiol Rev 2011; 35:790-819. [PMID: 21517914 DOI: 10.1111/j.1574-6976.2011.00273.x] [Citation(s) in RCA: 376] [Impact Index Per Article: 28.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Antibiotics were one of the great discoveries of the 20th century. However, resistance appeared even in the earliest years of the antibiotic era. Antibiotic resistance continues to become worse, despite the ever-increasing resources devoted to combat the problem. One of the most important factors in the development of resistance to antibiotics is the remarkable ability of bacteria to share genetic resources via Lateral Gene Transfer (LGT). LGT occurs on a global scale, such that in theory, any gene in any organism anywhere in the microbial biosphere might be mobilized and spread. With sufficiently strong selection, any gene may spread to a point where it establishes a global presence. From an antibiotic resistance perspective, this means that a resistance phenotype can appear in a diverse range of infections around the globe nearly simultaneously. We discuss the forces and agents that make this LGT possible and argue that the problem of resistance can ultimately only be managed by understanding the problem from a broad ecological and evolutionary perspective. We also argue that human activities are exacerbating the problem by increasing the tempo of LGT and bacterial evolution for many traits that are important to humans.
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Affiliation(s)
- Hatch W Stokes
- The i3 Institute, University of Technology, Broadway 2007, Sydney, NSW, Australia.
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Spread of the qnrVC quinolone resistance determinant in Vibrio cholerae. Antimicrob Agents Chemother 2011; 55:457. [PMID: 21183688 DOI: 10.1128/aac.00998-10] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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Cambray G, Sanchez-Alberola N, Campoy S, Guerin É, Da Re S, González-Zorn B, Ploy MC, Barbé J, Mazel D, Erill I. Prevalence of SOS-mediated control of integron integrase expression as an adaptive trait of chromosomal and mobile integrons. Mob DNA 2011; 2:6. [PMID: 21529368 PMCID: PMC3108266 DOI: 10.1186/1759-8753-2-6] [Citation(s) in RCA: 96] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2010] [Accepted: 04/30/2011] [Indexed: 11/26/2022] Open
Abstract
Background Integrons are found in hundreds of environmental bacterial species, but are mainly known as the agents responsible for the capture and spread of antibiotic-resistance determinants between Gram-negative pathogens. The SOS response is a regulatory network under control of the repressor protein LexA targeted at addressing DNA damage, thus promoting genetic variation in times of stress. We recently reported a direct link between the SOS response and the expression of integron integrases in Vibrio cholerae and a plasmid-borne class 1 mobile integron. SOS regulation enhances cassette swapping and capture in stressful conditions, while freezing the integron in steady environments. We conducted a systematic study of available integron integrase promoter sequences to analyze the extent of this relationship across the Bacteria domain. Results Our results showed that LexA controls the expression of a large fraction of integron integrases by binding to Escherichia coli-like LexA binding sites. In addition, the results provide experimental validation of LexA control of the integrase gene for another Vibrio chromosomal integron and for a multiresistance plasmid harboring two integrons. There was a significant correlation between lack of LexA control and predicted inactivation of integrase genes, even though experimental evidence also indicates that LexA regulation may be lost to enhance expression of integron cassettes. Conclusions Ancestral-state reconstruction on an integron integrase phylogeny led us to conclude that the ancestral integron was already regulated by LexA. The data also indicated that SOS regulation has been actively preserved in mobile integrons and large chromosomal integrons, suggesting that unregulated integrase activity is selected against. Nonetheless, additional adaptations have probably arisen to cope with unregulated integrase activity. Identifying them may be fundamental in deciphering the uneven distribution of integrons in the Bacteria domain.
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Affiliation(s)
- Guillaume Cambray
- Institut Pasteur, Unité Plasticité du Génome Bactérien, CNRS URA 2171, 75015 Paris, France
| | - Neus Sanchez-Alberola
- Departament de Genètica i de Microbiologia, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain.,Department of Biological Sciences, University of Maryland Baltimore County, Baltimore 21228, USA
| | - Susana Campoy
- Departament de Genètica i de Microbiologia, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain
| | - Émilie Guerin
- Université de Limoges, Faculté de Médecine, EA3175, INSERM, Equipe Avenir, Limoges 87000, France
| | - Sandra Da Re
- Université de Limoges, Faculté de Médecine, EA3175, INSERM, Equipe Avenir, Limoges 87000, France
| | - Bruno González-Zorn
- Departamento de Sanidad Animal, Facultad de Veterinaria, and VISAVET, Universidad Complutense de Madrid, 28040 Madrid, Spain
| | - Marie-Cécile Ploy
- Université de Limoges, Faculté de Médecine, EA3175, INSERM, Equipe Avenir, Limoges 87000, France
| | - Jordi Barbé
- Department of Biological Sciences, University of Maryland Baltimore County, Baltimore 21228, USA
| | - Didier Mazel
- Institut Pasteur, Unité Plasticité du Génome Bactérien, CNRS URA 2171, 75015 Paris, France
| | - Ivan Erill
- Department of Biological Sciences, University of Maryland Baltimore County, Baltimore 21228, USA
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Hazen TH, Pan L, Gu JD, Sobecky PA. The contribution of mobile genetic elements to the evolution and ecology of Vibrios. FEMS Microbiol Ecol 2011; 74:485-99. [PMID: 20662928 DOI: 10.1111/j.1574-6941.2010.00937.x] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
An increase in the frequency of seafood-borne gastroenteritis in humans and Vibrio-related disease of fish and invertebrates has generated interest in the ecology of disease-causing Vibrios and the mechanisms driving their evolution. Genome sequencing studies have indicated a substantial contribution of horizontal gene transfer (HGT) to the evolution of Vibrios. Of particular interest is the contribution of HGT to the evolution of Vibrios pathogens and the adaptation of disease-causing Vibrios for survival in diverse environments. In this review, we discuss the diversity and distribution of mobile genetic elements (MGEs) isolated from Vibrios and the contribution of these elements to the expansion of the ecological and pathogenic niches of the host strain. Much of the research on Vibrio MGEs has focused on understanding phages and plasmids and we will primarily discuss the evolution of these elements and also briefly highlight the other diverse elements characterized from Vibrios, which includes genomic islands and conjugative elements.
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Affiliation(s)
- Tracy H Hazen
- School of Biology, Georgia Institute of Technology, Atlanta, GA, USA
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Huguet-Tapia JC, Badger JH, Loria R, Pettis GS. Streptomyces turgidiscabies Car8 contains a modular pathogenicity island that shares virulence genes with other actinobacterial plant pathogens. Plasmid 2011; 65:118-24. [DOI: 10.1016/j.plasmid.2010.11.002] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2010] [Revised: 11/02/2010] [Accepted: 11/08/2010] [Indexed: 10/18/2022]
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Larouche A, Roy PH. Effect of attC structure on cassette excision by integron integrases. Mob DNA 2011; 2:3. [PMID: 21332975 PMCID: PMC3053210 DOI: 10.1186/1759-8753-2-3] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2010] [Accepted: 02/18/2011] [Indexed: 11/10/2022] Open
Abstract
Background Integrons are genetic elements able to integrate and disseminate genes as cassettes by a site-specific recombination mechanism. These elements contain a gene coding for an integrase that carries out recombination by interacting with two different target sites; the attI site in cis with the integrase and the palindromic attC site of a gene cassette. Integron integrases (IntIs) bind specifically to the bottom strand of attC sites. The extrahelical bases resulting from folding of attC bottom strands are important for the recognition by integrases. These enzymes are directly involved in the accumulation and formation of new cassette arrangements in the variable region of integrons. Thus, it is important to better understand interactions between IntIs and their substrates. Results We compared the ability of five IntIs to carry out excision of several cassettes flanked by different attC sites. The results showed that for most cassettes, IntI1 was the most active integrase. However, IntI2*179E and SonIntIA could easily excise cassettes containing the attCdfrA1 site located upstream, whereas IntI1 and IntI3 had only a weak excision activity for these cassettes. Analysis of the secondary structure adopted by the bottom strand of attCdfrA1 has shown that the identity of the extrahelical bases and the distance between them (A-N7-8-C) differ from those of attCs contained in the cassettes most easily excisable by IntI1 (T-N6-G). We used the attCdfrA1 site upstream of the sat2 gene cassette as a template and varied the identity and spacing between the extrahelical bases in order to determine how these modifications influence the ability of IntI1, IntI2*179E, IntI3 and SonIntIA to excise cassettes. Our results show that IntI1 is more efficient in cassette excision using T-N6-G or T-N6-C attCs while IntI3 recognizes only a limited range of attCs. IntI2*179E and SonIntIA are more tolerant of changes to the identity and spacing of extrahelical bases. Conclusions This study provides new insights into the factors that influence the efficiency of cassette excision by integron integrases. It also suggests that IntI2 and SonIntIA have an evolutionary path that is different from IntI1 and IntI3, in their ability to recognize and excise cassettes.
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Affiliation(s)
- André Larouche
- Centre de Recherche en Infectiologie, Centre Hospitalier Universitaire de Québec, Québec, Canada.
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Vibrio cholerae triggers SOS and mutagenesis in response to a wide range of antibiotics: a route towards multiresistance. Antimicrob Agents Chemother 2011; 55:2438-41. [PMID: 21300836 DOI: 10.1128/aac.01549-10] [Citation(s) in RCA: 148] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Antibiotic resistance development has been linked to the bacterial SOS stress response. In Escherichia coli, fluoroquinolones are known to induce SOS, whereas other antibiotics, such as aminoglycosides, tetracycline, and chloramphenicol, do not. Here we address whether various antibiotics induce SOS in Vibrio cholerae. Reporter green fluorescent protein (GFP) fusions were used to measure the response of SOS-regulated promoters to subinhibitory concentrations of antibiotics. We show that unlike the situation with E. coli, all these antibiotics induce SOS in V. cholerae.
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Erauso G, Lakhal F, Bidault-Toffin A, Le Chevalier P, Bouloc P, Paillard C, Jacq A. Evidence for the role of horizontal transfer in generating pVT1, a large mosaic conjugative plasmid from the clam pathogen, Vibrio tapetis. PLoS One 2011; 6:e16759. [PMID: 21326607 PMCID: PMC3033894 DOI: 10.1371/journal.pone.0016759] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2010] [Accepted: 12/29/2010] [Indexed: 02/05/2023] Open
Abstract
The marine bacterium Vibrio tapetis is the causative agent of the brown ring disease, which affects the clam Ruditapes philippinarum and causes heavy economic losses in North of Europe and in Eastern Asia. Further characterization of V. tapetis isolates showed that all the investigated strains harbored at least one large plasmid. We determined the sequence of the 82,266 bp plasmid pVT1 from the CECT4600(T) reference strain and analyzed its genetic content. pVT1 is a mosaic plasmid closely related to several conjugative plasmids isolated from Vibrio vulnificus strains and was shown to be itself conjugative in Vibrios. In addition, it contains DNA regions that have similarity with several other plasmids from marine bacteria (Vibrio sp., Shewanella sp., Listonella anguillarum and Photobacterium profundum). pVT1 contains a number of mobile elements, including twelve Insertion Sequences or inactivated IS genes and an RS1 phage element related to the CTXphi phage of V. cholerae. The genetic organization of pVT1 underscores an important role of horizontal gene transfer through conjugative plasmid shuffling and transposition events in the acquisition of new genetic resources and in generating the pVT1 modular organization. In addition, pVT1 presents a copy number of 9, relatively high for a conjugative plasmid, and appears to belong to a new type of replicon, which may be specific to Vibrionaceae and Shewanelleacae.
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Affiliation(s)
- Gaël Erauso
- Laboratoire des Sciences de l'Environnement Marin, UMR 6539, Institut Universitaire Européen de la Mer, Université de Bretagne Occidentale, CNRS, Plouzané, France
| | - Fatma Lakhal
- Institut de Génétique et Microbiologie, UMR 8621, Université Paris-Sud 11, CNRS, IFR115, Orsay, France
| | - Adeline Bidault-Toffin
- Laboratoire des Sciences de l'Environnement Marin, UMR 6539, Institut Universitaire Européen de la Mer, Université de Bretagne Occidentale, CNRS, Plouzané, France
| | - Patrick Le Chevalier
- Laboratoire Universitaire de Biodiversité et Ecologie Microbienne, Université de Bretagne Occidentale, Quimper, France
| | - Philippe Bouloc
- Institut de Génétique et Microbiologie, UMR 8621, Université Paris-Sud 11, CNRS, IFR115, Orsay, France
| | - Christine Paillard
- Laboratoire des Sciences de l'Environnement Marin, UMR 6539, Institut Universitaire Européen de la Mer, Université de Bretagne Occidentale, CNRS, Plouzané, France
| | - Annick Jacq
- Institut de Génétique et Microbiologie, UMR 8621, Université Paris-Sud 11, CNRS, IFR115, Orsay, France
- * E-mail:
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Affiliation(s)
- Guillaume Cambray,
- Institut Pasteur, Unité Plasticité du Génome Bactérien, Département Génomes et Génétique, F-75015 Paris, France;
- CNRS, URA2171, F-75015 Paris, France
| | - Anne-Marie Guerout,
- Institut Pasteur, Unité Plasticité du Génome Bactérien, Département Génomes et Génétique, F-75015 Paris, France;
- CNRS, URA2171, F-75015 Paris, France
| | - Didier Mazel
- Institut Pasteur, Unité Plasticité du Génome Bactérien, Département Génomes et Génétique, F-75015 Paris, France;
- CNRS, URA2171, F-75015 Paris, France
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Baharoglu Z, Bikard D, Mazel D. Conjugative DNA transfer induces the bacterial SOS response and promotes antibiotic resistance development through integron activation. PLoS Genet 2010; 6:e1001165. [PMID: 20975940 PMCID: PMC2958807 DOI: 10.1371/journal.pgen.1001165] [Citation(s) in RCA: 189] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2010] [Accepted: 09/17/2010] [Indexed: 11/21/2022] Open
Abstract
Conjugation is one mechanism for intra- and inter-species horizontal gene transfer among bacteria. Conjugative elements have been instrumental in many bacterial species to face the threat of antibiotics, by allowing them to evolve and adapt to these hostile conditions. Conjugative plasmids are transferred to plasmidless recipient cells as single-stranded DNA. We used lacZ and gfp fusions to address whether conjugation induces the SOS response and the integron integrase. The SOS response controls a series of genes responsible for DNA damage repair, which can lead to recombination and mutagenesis. In this manuscript, we show that conjugative transfer of ssDNA induces the bacterial SOS stress response, unless an anti-SOS factor is present to alleviate this response. We also show that integron integrases are up-regulated during this process, resulting in increased cassette rearrangements. Moreover, the data we obtained using broad and narrow host range plasmids strongly suggests that plasmid transfer, even abortive, can trigger chromosomal gene rearrangements and transcriptional switches in the recipient cell. Our results highlight the importance of environments concentrating disparate bacterial communities as reactors for extensive genetic adaptation of bacteria. Bacteria exchange DNA in their natural environments. The process called conjugation consists of DNA transfer by cell contact from one bacterium to another. Conjugative circular plasmids have been identified as shuttles and reservoirs for adaptive genes. It is now established that such lateral gene transfer plays an essential role, especially for the antibiotic resistance development and dissemination among bacteria. Moreover, integrons, platforms of mobile gene cassettes, have been instrumental in this phenomenon, through their successful association with conjugative resistance plasmids. We demonstrate in this study that the conjugative transfer of plasmids triggers a bacterial stress response—the SOS response—in recipient cells and can impact the cassette content of integrons. The SOS response is already known to induce various genome modifications. Human and animal pathogens cohabit with environmental bacteria, in niches which will favor DNA exchange. SOS induction during conjugation is thus most probably able to impact a wide range of genomes. Bacterial SOS response could then be a suitable target for co-treatment of infections in order to prevent exchange of antibiotic resistance/adaptation genes.
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Affiliation(s)
- Zeynep Baharoglu
- Institut Pasteur, Unité Plasticité du Génome Bactérien, Département Génomes et Génétique, Paris, France
- CNRS, URA2171, Paris, France
| | - David Bikard
- Institut Pasteur, Unité Plasticité du Génome Bactérien, Département Génomes et Génétique, Paris, France
- CNRS, URA2171, Paris, France
| | - Didier Mazel
- Institut Pasteur, Unité Plasticité du Génome Bactérien, Département Génomes et Génétique, Paris, France
- CNRS, URA2171, Paris, France
- * E-mail:
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Johansson C, Boukharta L, Eriksson J, Aqvist J, Sundström L. Mutagenesis and homology modeling of the Tn21 integron integrase IntI1. Biochemistry 2010; 48:1743-53. [PMID: 19199791 DOI: 10.1021/bi8020235] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Horizontal DNA transfer between bacteria is widespread and a major cause of antibiotic resistance. For logistic reasons, single or combined genes are shuttled between vectors such as plasmids and bacterial chromosomes. Special elements termed integrons operate in such shuttling and are therefore vital for horizontal gene transfer. Shorter elements carrying genes, cassettes, are integrated in the integrons, or excised from them, by virtue of a recombination site, attC, positioned in the 3' end of each unit. It is a remarkable and possibly restricting elementary feature of attC that it must be single-stranded while the partner target site, attI, may be double-stranded. The integron integrases belong to the tyrosine recombinase family, and this work reports mutations of the integrase IntI1 from transposon Tn21, chosen within a well-conserved region characteristic of the integron integrases. The mutated proteins were tested for binding to a bottom strand of an attC substrate, by using an electrophoresis mobility shift assay. To aid in interpreting the results, a homology model was constructed on the basis of the crystal structure of integron integrase VchIntIA from Vibrio cholerae bound to its cognate attC substrate VCRbs. The local stability and hydrogen bonding network of key domains of the modeled structure were further examined using molecular dynamics simulations. The homology model allowed us to interpret the roles of several amino acid residues, four of which were clearly binding assay responsive upon mutagenesis. Notably, we also observed features indicating that IntI1 may be more prone to base-specific contacts with VCRbs than VchIntIA.
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Affiliation(s)
- Carolina Johansson
- Department of Medical Biochemistry and Microbiology, Uppsala University, BMC, Box 582, 751 23 Uppsala, Sweden
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Bikard D, Julié-Galau S, Cambray G, Mazel D. The synthetic integron: an in vivo genetic shuffling device. Nucleic Acids Res 2010; 38:e153. [PMID: 20534632 PMCID: PMC2926619 DOI: 10.1093/nar/gkq511] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
As the field of synthetic biology expands, strategies and tools for the rapid construction of new biochemical pathways will become increasingly valuable. Purely rational design of complex biological pathways is inherently limited by the current state of our knowledge. Selection of optimal arrangements of genetic elements from randomized libraries may well be a useful approach for successful engineering. Here, we propose the construction and optimization of metabolic pathways using the inherent gene shuffling activity of a natural bacterial site-specific recombination system, the integron. As a proof of principle, we constructed and optimized a functional tryptophan biosynthetic operon in Escherichia coli. The trpA-E genes along with ‘regulatory’ elements were delivered as individual recombination cassettes in a synthetic integron platform. Integrase-mediated recombination generated thousands of genetic combinations overnight. We were able to isolate a large number of arrangements displaying varying fitness and tryptophan production capacities. Several assemblages required as many as six recombination events and produced as much as 11-fold more tryptophan than the natural gene order in the same context.
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Affiliation(s)
- David Bikard
- Institut Pasteur, Département Génomes et Génétique, Paris, France
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Inverse correlation between promoter strength and excision activity in class 1 integrons. PLoS Genet 2010; 6:e1000793. [PMID: 20066027 PMCID: PMC2791841 DOI: 10.1371/journal.pgen.1000793] [Citation(s) in RCA: 138] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2009] [Accepted: 11/27/2009] [Indexed: 01/24/2023] Open
Abstract
Class 1 integrons are widespread genetic elements that allow bacteria to capture and express gene cassettes that are usually promoterless. These integrons play a major role in the dissemination of antibiotic resistance among Gram-negative bacteria. They typically consist of a gene (intI) encoding an integrase (that catalyzes the gene cassette movement by site-specific recombination), a recombination site (attI1), and a promoter (Pc) responsible for the expression of inserted gene cassettes. The Pc promoter can occasionally be combined with a second promoter designated P2, and several Pc variants with different strengths have been described, although their relative distribution is not known. The Pc promoter in class 1 integrons is located within the intI1 coding sequence. The Pc polymorphism affects the amino acid sequence of IntI1 and the effect of this feature on the integrase recombination activity has not previously been investigated. We therefore conducted an extensive in silico study of class 1 integron sequences in order to assess the distribution of Pc variants. We also measured these promoters' strength by means of transcriptional reporter gene fusion experiments and estimated the excision and integration activities of the different IntI1 variants. We found that there are currently 13 Pc variants, leading to 10 IntI1 variants, that have a highly uneven distribution. There are five main Pc-P2 combinations, corresponding to five promoter strengths, and three main integrases displaying similar integration activity but very different excision efficiency. Promoter strength correlates with integrase excision activity: the weaker the promoter, the stronger the integrase. The tight relationship between the aptitude of class 1 integrons to recombine cassettes and express gene cassettes may be a key to understanding the short-term evolution of integrons. Dissemination of integron-driven drug resistance is therefore more complex than previously thought.
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Abstract
Ciprofloxacin was introduced for treatment of patients with cholera in Bangladesh because of resistance to other agents, but its utility has been compromised by the decreasing ciprofloxacin susceptibility of Vibrio cholerae over time. We correlated levels of susceptibility and temporal patterns with the occurrence of mutation in gyrA, which encodes a subunit of DNA gyrase, followed by mutation in parC, which encodes a subunit of DNA topoisomerase IV. We found that ciprofloxacin activity was more recently further compromised in strains containing qnrVC3, which encodes a pentapeptide repeat protein of the Qnr subfamily, members of which protect topoisomerases from quinolone action. We show that qnrVC3 confers transferable low-level quinolone resistance and is present within a member of the SXT integrating conjugative element family found commonly on the chromosomes of multidrug-resistant strains of V. cholerae and on the chromosomes of Escherichia coli transconjugants constructed in the laboratory. Thus, progressive increases in quinolone resistance in V. cholerae are linked to cumulative mutations in quinolone targets and most recently to a qnr gene on a mobile multidrug resistance element, resulting in further challenges for the antimicrobial therapy of cholera.
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