1
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Richard E, Darracq B, Littner E, Millot GA, Conte V, Cokelaer T, Engelstädter J, Rocha EPC, Mazel D, Loot C. Belt and braces: Two escape ways to maintain the cassette reservoir of large chromosomal integrons. PLoS Genet 2024; 20:e1011231. [PMID: 38578806 PMCID: PMC11023631 DOI: 10.1371/journal.pgen.1011231] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2023] [Revised: 04/17/2024] [Accepted: 03/19/2024] [Indexed: 04/07/2024] Open
Abstract
Integrons are adaptive devices that capture, stockpile, shuffle and express gene cassettes thereby sampling combinatorial phenotypic diversity. Some integrons called sedentary chromosomal integrons (SCIs) can be massive structures containing hundreds of cassettes. Since most of these cassettes are non-expressed, it is not clear how they remain stable over long evolutionary timescales. Recently, it was found that the experimental inversion of the SCI of Vibrio cholerae led to a dramatic increase of the cassette excision rate associated with a fitness defect. Here, we question the evolutionary sustainability of this apparently counter selected genetic context. Through experimental evolution, we find that the integrase is rapidly inactivated and that the inverted SCI can recover its original orientation by homologous recombination between two insertion sequences (ISs) present in the array. These two outcomes of SCI inversion restore the normal growth and prevent the loss of cassettes, enabling SCIs to retain their roles as reservoirs of functions. These results illustrate a nice interplay between gene orientation, genome rearrangement, bacterial fitness and demonstrate how integrons can benefit from their embedded ISs.
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Affiliation(s)
- Egill Richard
- Institut Pasteur, Université Paris Cité, CNRS UMR3525, Unité Plasticité du Génome Bactérien, Paris, France
- Sorbonne Université, ED515, Paris, France
| | - Baptiste Darracq
- Institut Pasteur, Université Paris Cité, CNRS UMR3525, Unité Plasticité du Génome Bactérien, Paris, France
- Sorbonne Université, ED515, Paris, France
| | - Eloi Littner
- Sorbonne Université, ED515, Paris, France
- Institut Pasteur, Université Paris Cité, CNRS UMR3525, Microbial Evolutionary Genomics, Paris, France
- DGA CBRN Defence, Vert-le-Petit, France
| | - Gael A. Millot
- Institut Pasteur, Université Paris Cité, Bioinformatics and Biostatistics Hub, Paris, France
| | - Valentin Conte
- Institut Pasteur, Université Paris Cité, CNRS UMR3525, Unité Plasticité du Génome Bactérien, Paris, France
| | - Thomas Cokelaer
- Institut Pasteur, Université Paris Cité, Bioinformatics and Biostatistics Hub, Paris, France
- Institut Pasteur, Université Paris Cité, Plateforme Technologique Biomics, Paris, France
| | - Jan Engelstädter
- School of the Environment, The University of Queensland, Brisbane, Australia
| | - Eduardo P. C. Rocha
- Institut Pasteur, Université Paris Cité, CNRS UMR3525, Microbial Evolutionary Genomics, Paris, France
| | - Didier Mazel
- Institut Pasteur, Université Paris Cité, CNRS UMR3525, Unité Plasticité du Génome Bactérien, Paris, France
| | - Céline Loot
- Institut Pasteur, Université Paris Cité, CNRS UMR3525, Unité Plasticité du Génome Bactérien, Paris, France
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2
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Richard E, Darracq B, Littner E, Vit C, Whiteway C, Bos J, Fournes F, Garriss G, Conte V, Lapaillerie D, Parissi V, Rousset F, Skovgaard O, Bikard D, Rocha EPC, Mazel D, Loot C. Cassette recombination dynamics within chromosomal integrons are regulated by toxin-antitoxin systems. SCIENCE ADVANCES 2024; 10:eadj3498. [PMID: 38215203 DOI: 10.1126/sciadv.adj3498] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2023] [Accepted: 12/14/2023] [Indexed: 01/14/2024]
Abstract
Integrons are adaptive bacterial devices that rearrange promoter-less gene cassettes into variable ordered arrays under stress conditions, thereby sampling combinatorial phenotypic diversity. Chromosomal integrons often carry hundreds of silent gene cassettes, with integrase-mediated recombination leading to rampant DNA excision and integration, posing a potential threat to genome integrity. How this activity is regulated and controlled, particularly through selective pressures, to maintain such large cassette arrays is unknown. Here, we show a key role of promoter-containing toxin-antitoxin (TA) cassettes as systems that kill the cell when the overall cassette excision rate is too high. These results highlight the importance of TA cassettes regulating the cassette recombination dynamics and provide insight into the evolution and success of integrons in bacterial genomes.
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Affiliation(s)
- Egill Richard
- Institut Pasteur, Université Paris Cité, CNRS UMR3525, Unité Plasticité du Génome Bactérien, 75015 Paris, France
- Sorbonne Université, ED515, F-75005 Paris, France
| | - Baptiste Darracq
- Institut Pasteur, Université Paris Cité, CNRS UMR3525, Unité Plasticité du Génome Bactérien, 75015 Paris, France
- Sorbonne Université, ED515, F-75005 Paris, France
| | - Eloi Littner
- Sorbonne Université, ED515, F-75005 Paris, France
- Institut Pasteur, Université Paris Cité, CNRS UMR3525, Microbial Evolutionary Genomics, 75015 Paris, France
- DGA CBRN Defence, 91710 Vert-le-Petit, France
| | - Claire Vit
- Institut Pasteur, Université Paris Cité, CNRS UMR3525, Unité Plasticité du Génome Bactérien, 75015 Paris, France
- Sorbonne Université, ED515, F-75005 Paris, France
| | - Clémence Whiteway
- Institut Pasteur, Université Paris Cité, CNRS UMR3525, Unité Plasticité du Génome Bactérien, 75015 Paris, France
| | - Julia Bos
- Institut Pasteur, Université Paris Cité, CNRS UMR3525, Unité Plasticité du Génome Bactérien, 75015 Paris, France
| | - Florian Fournes
- Institut Pasteur, Université Paris Cité, CNRS UMR3525, Unité Plasticité du Génome Bactérien, 75015 Paris, France
| | - Geneviève Garriss
- Institut Pasteur, Université Paris Cité, CNRS UMR3525, Unité Plasticité du Génome Bactérien, 75015 Paris, France
| | - Valentin Conte
- Institut Pasteur, Université Paris Cité, CNRS UMR3525, Unité Plasticité du Génome Bactérien, 75015 Paris, France
| | - Delphine Lapaillerie
- University of Bordeaux, Fundamental Microbiology and Pathogenicity Laboratory, CNRS, UMR 5234, SFR TransBioMed, Bordeaux, France
- Viral DNA Integration and Chromatin Dynamics Network (DyNAVir), France
| | - Vincent Parissi
- University of Bordeaux, Fundamental Microbiology and Pathogenicity Laboratory, CNRS, UMR 5234, SFR TransBioMed, Bordeaux, France
- Viral DNA Integration and Chromatin Dynamics Network (DyNAVir), France
| | - François Rousset
- Institut Pasteur, Université Paris Cité, CNRS UMR6047, Synthetic Biology, 75015 Paris, France
| | - Ole Skovgaard
- Department of Science, Systems and Models, Roskilde University, Roskilde DK-4000, Denmark
| | - David Bikard
- Institut Pasteur, Université Paris Cité, CNRS UMR6047, Synthetic Biology, 75015 Paris, France
| | - Eduardo P C Rocha
- Institut Pasteur, Université Paris Cité, CNRS UMR3525, Microbial Evolutionary Genomics, 75015 Paris, France
| | - 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
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3
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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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4
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Ghaly TM, Rajabal V, Penesyan A, Coleman NV, Paulsen IT, Gillings MR, Tetu SG. Functional enrichment of integrons: Facilitators of antimicrobial resistance and niche adaptation. iScience 2023; 26:108301. [PMID: 38026211 PMCID: PMC10661359 DOI: 10.1016/j.isci.2023.108301] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2023] [Revised: 10/11/2023] [Accepted: 10/19/2023] [Indexed: 12/01/2023] Open
Abstract
Integrons are genetic elements, found among diverse bacteria and archaea, that capture and rearrange gene cassettes to rapidly generate genetic diversity and drive adaptation. Despite their broad taxonomic and geographic prevalence, and their role in microbial adaptation, the functions of gene cassettes remain poorly characterized. Here, using a combination of bioinformatic and experimental analyses, we examined the functional diversity of gene cassettes from different environments. We find that cassettes encode diverse antimicrobial resistance (AMR) determinants, including those conferring resistance to antibiotics currently in the developmental pipeline. Further, we find a subset of cassette functions is universally enriched relative to their broader metagenomes. These are largely involved in (a)biotic interactions, including AMR, phage defense, virulence, biodegradation, and stress tolerance. The remainder of functions are sample-specific, suggesting that they confer localised functions relevant to their microenvironment. Together, they comprise functional profiles different from bulk metagenomes, representing niche-adaptive components of the prokaryotic pangenome.
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Affiliation(s)
- Timothy M. Ghaly
- School of Natural Sciences, Macquarie University, New South Wales 2109, Australia
| | - Vaheesan Rajabal
- School of Natural Sciences, Macquarie University, New South Wales 2109, Australia
- ARC Centre of Excellence in Synthetic Biology, Macquarie University, New South Wales 2109, Australia
| | - Anahit Penesyan
- School of Natural Sciences, Macquarie University, New South Wales 2109, Australia
- ARC Centre of Excellence in Synthetic Biology, Macquarie University, New South Wales 2109, Australia
| | - Nicholas V. Coleman
- School of Natural Sciences, Macquarie University, New South Wales 2109, Australia
| | - Ian T. Paulsen
- School of Natural Sciences, Macquarie University, New South Wales 2109, Australia
- ARC Centre of Excellence in Synthetic Biology, Macquarie University, New South Wales 2109, Australia
| | - Michael R. Gillings
- School of Natural Sciences, Macquarie University, New South Wales 2109, Australia
- ARC Centre of Excellence in Synthetic Biology, Macquarie University, New South Wales 2109, Australia
| | - Sasha G. Tetu
- School of Natural Sciences, Macquarie University, New South Wales 2109, Australia
- ARC Centre of Excellence in Synthetic Biology, Macquarie University, New South Wales 2109, Australia
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5
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Zhu Y, Wang T, Zhu W, Wei Q. Influence of class 2 integron integrase concentration on gene cassette insertion and excision in vivo. Braz J Microbiol 2023; 54:645-653. [PMID: 36808308 PMCID: PMC10235263 DOI: 10.1007/s42770-023-00926-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Accepted: 02/07/2023] [Indexed: 02/23/2023] Open
Abstract
Integron can capture and express antimicrobial resistance gene cassettes and plays important roles in horizontal gene transfer. The establishment of a complete in vitro reaction system will help to reveal integron integrase mediated site-specific recombination process and regulation mechanism. As an enzymatic reaction, the concentration of integrase is assumed to have a great influence on the reaction rate. To determine the influence of different concentrations of integrase on the reaction rate and to find the best range of enzyme concentration were essential to optimizing the in vitro reaction system. In this study, plasmids with gradient transcription levels of class 2 integron integrase gene intI2 under different promoters were constructed. Among plasmids pI2W16, pINTI2N, pI2W, and pI2NW, intI2 transcription levels ranged from about 0.61-fold to 49.65-fold of that in pINTI2N. And the frequencies of gene cassette sat2 integration and excision catalyzed by IntI2 were positively correlated with the transcription levels of intI2 within this range. Western blotting results indicated high expression of IntI2 partly existed in the form of an inclusion body. When compared with Pc of class 1 integron, the spacer sequence of PintI2 can increase the strength of PcW but decrease the strength of PcS. In conclusion, the frequencies of gene cassette integration and excision were positively correlated with the concentration of IntI2. intI2 driving by PcW with PintI2 spacer sequence can obtain the optimum IntI2 concentration required to achieve the maximum recombination efficiency in vivo in this study.
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Affiliation(s)
- Yu Zhu
- Department of Laboratory Medicine, Anhui University of Science and Technology Affiliated Fengxian Hospital, 6600 Nanfeng Road, Shanghai, 201499, China
| | - Tong Wang
- Department of Laboratory Medicine, Anhui University of Science and Technology Affiliated Fengxian Hospital, 6600 Nanfeng Road, Shanghai, 201499, China
| | - Wenwen Zhu
- Department of Laboratory Medicine, Southern Medical University Affiliated Fengxian Hospital, 6600 Nanfeng Road, Shanghai, 201499, China
| | - Quhao Wei
- Department of Laboratory Medicine, Anhui University of Science and Technology Affiliated Fengxian Hospital, 6600 Nanfeng Road, Shanghai, 201499, China.
- Department of Laboratory Medicine, Southern Medical University Affiliated Fengxian Hospital, 6600 Nanfeng Road, Shanghai, 201499, China.
- Department of Laboratory Medicine, Shanghai University of Medicine & Health Sciences Affiliated Sixth People's Hospital South Campus, 6600 Nanfeng Road, Shanghai, 201499, China.
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6
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Sanchez-Cid C, Ghaly TM, Gillings MR, Vogel TM. Sub-inhibitory gentamicin pollution induces gentamicin resistance gene integration in class 1 integrons in the environment. Sci Rep 2023; 13:8612. [PMID: 37244902 DOI: 10.1038/s41598-023-35074-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2023] [Accepted: 05/12/2023] [Indexed: 05/29/2023] Open
Abstract
Antibiotics at sub-inhibitory concentrations are often found in the environment. Here they could impose selective pressure on bacteria, leading to the selection and dissemination of antibiotic resistance, despite being under the inhibitory threshold. The goal of this study was to evaluate the effects of sub-inhibitory concentrations of gentamicin on environmental class 1 integron cassettes in natural river microbial communities. Gentamicin at sub-inhibitory concentrations promoted the integration and selection of gentamicin resistance genes (GmRG) in class 1 integrons after only a one-day exposure. Therefore, sub-inhibitory concentrations of gentamicin induced integron rearrangements, increasing the mobilization potential of gentamicin resistance genes and potentially increasing their dissemination in the environment. This study demonstrates the effects of antibiotics at sub-inhibitory concentrations in the environment and supports concerns about antibiotics as emerging pollutants.
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Affiliation(s)
- Concepcion Sanchez-Cid
- Environmental Microbial Genomics, UMR 5005 Laboratoire Ampère, CNRS, École Centrale de Lyon, Université de Lyon, Écully, France.
| | - Timothy M Ghaly
- School of Natural Sciences, Macquarie University, NSW, 2109, Australia
| | - Michael R Gillings
- School of Natural Sciences, Macquarie University, NSW, 2109, Australia
- ARC Centre of Excellence in Synthetic Biology, Macquarie University, NSW, 2109, Australia
| | - Timothy M Vogel
- Université de Lyon, Université Claude Bernard Lyon 1, UMR CNRS 5557, UMR INRAe 1418, VetAgro Sup, Ecologie Microbienne, F-69622, Villeurbanne, France
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7
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Off-Target Integron Activity Leads to Rapid Plasmid Compensatory Evolution in Response to Antibiotic Selection Pressure. mBio 2023; 14:e0253722. [PMID: 36840554 PMCID: PMC10127599 DOI: 10.1128/mbio.02537-22] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/24/2023] Open
Abstract
Integrons are mobile genetic elements that have played an important role in the dissemination of antibiotic resistance. Under stress, the integron can generate combinatorial variation in resistance cassette expression by cassette reshuffling, accelerating the evolution of resistance. However, the flexibility of the integron integrase site recognition motif hints at potential off-target effects of the integrase on the rest of the genome that may have important evolutionary consequences. Here, we test this hypothesis by selecting for increased-piperacillin-resistance populations of Pseudomonas aeruginosa with a mobile integron containing a difficult-to-mobilize β-lactamase cassette to minimize the potential for adaptive cassette reshuffling. We found that integron activity can decrease the overall survival rate but also improve the fitness of the surviving populations. Off-target inversions mediated by the integron accelerated plasmid adaptation by disrupting costly conjugative genes otherwise mutated in control populations lacking a functional integrase. Plasmids containing integron-mediated inversions were associated with lower plasmid costs and higher stability than plasmids carrying mutations albeit at the cost of a reduced conjugative ability. These findings highlight the potential for integrons to create structural variation that can drive bacterial evolution, and they provide an interesting example showing how antibiotic pressure can drive the loss of conjugative genes. IMPORTANCE Tackling the public health challenge created by antibiotic resistance requires understanding the mechanisms driving its evolution. Mobile integrons are widespread genetic platforms heavily involved in the spread of antibiotic resistance. Through the action of the integrase enzyme, integrons allow bacteria to capture, excise, and shuffle antibiotic resistance gene cassettes. This integrase enzyme is characterized by its ability to recognize a wide range of recombination sites, which allows it to easily capture diverse resistance cassettes but which may also lead to off-target reactions with the rest of the genome. Using experimental evolution, we tested the off-target impact of integron activity. We found that integrons increased the fitness of the surviving bacteria through extensive genomic rearrangements of the plasmids carrying the integrons, reducing their ability to spread horizontally. These results show that integrons not only accelerate resistance evolution but also can generate extensive structural variation, driving bacterial evolution beyond antibiotic resistance.
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8
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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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9
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Ghaly TM, Tetu SG, Penesyan A, Qi Q, Rajabal V, Gillings MR. Discovery of integrons in Archaea: Platforms for cross-domain gene transfer. SCIENCE ADVANCES 2022; 8:eabq6376. [PMID: 36383678 PMCID: PMC9668308 DOI: 10.1126/sciadv.abq6376] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/21/2022] [Accepted: 10/19/2022] [Indexed: 06/16/2023]
Abstract
Horizontal gene transfer between different domains of life is increasingly being recognized as an important evolutionary driver, with the potential to increase the pace of biochemical innovation and environmental adaptation. However, the mechanisms underlying the recruitment of exogenous genes from foreign domains are mostly unknown. Integrons are a family of genetic elements that facilitate this process within Bacteria. However, they have not been reported outside Bacteria, and thus their potential role in cross-domain gene transfer has not been investigated. Here, we discover that integrons are also present in 75 archaeal metagenome-assembled genomes from nine phyla, and are particularly enriched among Asgard archaea. Furthermore, we provide experimental evidence that integrons can facilitate the recruitment of archaeal genes by bacteria. Our findings establish a previously unknown mechanism of cross-domain gene transfer whereby bacteria can incorporate archaeal genes from their surrounding environment via integron activity. These findings have important implications for prokaryotic ecology and evolution.
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Affiliation(s)
- Timothy M. Ghaly
- School of Natural Sciences, Macquarie University, Sydney, New South Wales 2109, Australia
| | - Sasha G. Tetu
- School of Natural Sciences, Macquarie University, Sydney, New South Wales 2109, Australia
- ARC Centre of Excellence in Synthetic Biology, Macquarie University, Sydney, New South Wales 2109, Australia
| | - Anahit Penesyan
- School of Natural Sciences, Macquarie University, Sydney, New South Wales 2109, Australia
- ARC Centre of Excellence in Synthetic Biology, Macquarie University, Sydney, New South Wales 2109, Australia
| | - Qin Qi
- School of Natural Sciences, Macquarie University, Sydney, New South Wales 2109, Australia
| | - Vaheesan Rajabal
- School of Natural Sciences, Macquarie University, Sydney, New South Wales 2109, Australia
- ARC Centre of Excellence in Synthetic Biology, Macquarie University, Sydney, New South Wales 2109, Australia
| | - Michael R. Gillings
- School of Natural Sciences, Macquarie University, Sydney, New South Wales 2109, Australia
- ARC Centre of Excellence in Synthetic Biology, Macquarie University, Sydney, New South Wales 2109, Australia
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10
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Zhu W, Wang T, Zhu Y, Xiao L, Liu W, Wei Q. Two-dimensional PCR for detecting class 1, 2 and 3 integrons. Heliyon 2022; 8:e11844. [DOI: 10.1016/j.heliyon.2022.e11844] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2022] [Revised: 09/29/2022] [Accepted: 11/17/2022] [Indexed: 11/27/2022] Open
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11
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Ghaly TM, Penesyan A, Pritchard A, Qi Q, Rajabal V, Tetu SG, Gillings MR. Methods for the targeted sequencing and analysis of integrons and their gene cassettes from complex microbial communities. Microb Genom 2022; 8. [PMID: 35298369 PMCID: PMC9176274 DOI: 10.1099/mgen.0.000788] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Integrons are microbial genetic elements that can integrate mobile gene cassettes. They are mostly known for spreading antibiotic resistance cassettes among human pathogens. However, beyond clinical settings, gene cassettes encode an extraordinarily diverse range of functions important for bacterial adaptation. The recovery and sequencing of cassettes has promising applications, including: surveillance of clinically important genes, particularly antibiotic resistance determinants; investigating the functional diversity of integron-carrying bacteria; and novel enzyme discovery. Although gene cassettes can be directly recovered using PCR, there are no standardised methods for their amplification and, importantly, for validating sequences as genuine integron gene cassettes. Here, we present reproducible methods for the amplification, sequence processing, and validation of gene cassette amplicons from complex communities. We describe two different PCR assays that either amplify cassettes together with integron integrases, or gene cassettes together within cassette arrays. We compare the performance of Nanopore and Illumina sequencing, and present bioinformatic pipelines that filter sequences to ensure that they represent amplicons from genuine integrons. Using a diverse set of environmental DNAs, we show that our approach can consistently recover thousands of unique cassettes per sample and up to hundreds of different integron integrases. Recovered cassettes confer a wide range of functions, including antibiotic resistance, with as many as 300 resistance cassettes found in a single sample. In particular, we show that class one integrons are collecting and concentrating resistance genes out of the broader diversity of cassette functions. The methods described here can be applied to any environmental or clinical microbiome sample.
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Affiliation(s)
- Timothy M Ghaly
- School of Natural Sciences, Macquarie University, New South Wales 2109, Australia
| | - Anahit Penesyan
- School of Natural Sciences, Macquarie University, New South Wales 2109, Australia.,ARC Centre of Excellence in Synthetic Biology, Macquarie University, New South Wales 2109, Australia
| | - Alexander Pritchard
- Division of Food Sciences, University of Nottingham, Loughborough LE12 5RD, Australia
| | - Qin Qi
- School of Natural Sciences, Macquarie University, New South Wales 2109, Australia
| | - Vaheesan Rajabal
- School of Natural Sciences, Macquarie University, New South Wales 2109, Australia.,ARC Centre of Excellence in Synthetic Biology, Macquarie University, New South Wales 2109, Australia
| | - Sasha G Tetu
- School of Natural Sciences, Macquarie University, New South Wales 2109, Australia.,ARC Centre of Excellence in Synthetic Biology, Macquarie University, New South Wales 2109, Australia
| | - Michael R Gillings
- School of Natural Sciences, Macquarie University, New South Wales 2109, Australia.,ARC Centre of Excellence in Synthetic Biology, Macquarie University, New South Wales 2109, Australia
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12
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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: 2] [Impact Index Per Article: 1.0] [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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13
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Fonseca ÉL, Vicente AC. Integron Functionality and Genome Innovation: An Update on the Subtle and Smart Strategy of Integrase and Gene Cassette Expression Regulation. Microorganisms 2022; 10:microorganisms10020224. [PMID: 35208680 PMCID: PMC8876359 DOI: 10.3390/microorganisms10020224] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Revised: 01/14/2022] [Accepted: 01/15/2022] [Indexed: 12/22/2022] Open
Abstract
Integrons are considered hot spots for bacterial evolution, since these platforms allow one-step genomic innovation by capturing and expressing genes that provide advantageous novelties, such as antibiotic resistance. The acquisition and shuffling of gene cassettes featured by integrons enable the population to rapidly respond to changing selective pressures. However, in order to avoid deleterious effects and fitness burden, the integron activity must be tightly controlled, which happens in an elegant and elaborate fashion, as discussed in detail in the present review. Here, we aimed to provide an up-to-date overview of the complex regulatory networks that permeate the expression and functionality of integrons at both transcriptional and translational levels. It was possible to compile strong shreds of evidence clearly proving that these versatile platforms include functions other than acquiring and expressing gene cassettes. The well-balanced mechanism of integron expression is intricately related with environmental signals, host cell physiology, fitness, and survival, ultimately leading to adaptation on the demand.
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14
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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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15
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Corneloup A, Caumont-Sarcos A, Kamgoue A, Marty B, Le PTN, Siguier P, Guynet C, Ton-Hoang B. TnpAREP and REP sequences dissemination in bacterial genomes: REP recognition determinants. Nucleic Acids Res 2021; 49:6982-6995. [PMID: 34161591 PMCID: PMC8266576 DOI: 10.1093/nar/gkab524] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2020] [Revised: 05/27/2021] [Accepted: 06/17/2021] [Indexed: 11/12/2022] Open
Abstract
REP, diverse palindromic DNA sequences found at high copy number in many bacterial genomes, have been attributed important roles in cell physiology but their dissemination mechanisms are poorly understood. They might represent non-autonomous transposable elements mobilizable by TnpAREP, the first prokaryotic domesticated transposase associated with REP. TnpAREP, fundamentally different from classical transposases, are members of the HuH superfamily and closely related to the transposases of the IS200/IS605 family. We previously showed that Escherichia coli TnpAREP processes cognate single stranded REP in vitro and that this activity requires the integrity of the REP structure, in particular imperfect palindromes interrupted by a bulge and preceded by a conserved DNA motif. A second group of REPs rather carry perfect palindromes, raising questions about how the latter are recognized by their cognate TnpAREP. To get insight into the importance of REP structural and sequence determinants in these two groups, we developed an in vitro activity assay coupled to a mutational analysis for three different TnpAREP/REP duos via a SELEX approach. We also tackled the question of how the cleavage site is selected. This study revealed that two TnpAREP groups have co-evolved with their cognate REPs and use different strategies to recognize their REP substrates.
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Affiliation(s)
- Alix Corneloup
- Laboratoire de Microbiologie et de Génétique Moléculaires (LMGM), CBI, CNRS, Université Toulouse UPS, Toulouse, France
| | - Anne Caumont-Sarcos
- Laboratoire de Microbiologie et de Génétique Moléculaires (LMGM), CBI, CNRS, Université Toulouse UPS, Toulouse, France
| | | | - Brigitte Marty
- Laboratoire de Microbiologie et de Génétique Moléculaires (LMGM), CBI, CNRS, Université Toulouse UPS, Toulouse, France
| | - Phan Thai Nguyen Le
- Laboratoire de Microbiologie et de Génétique Moléculaires (LMGM), CBI, CNRS, Université Toulouse UPS, Toulouse, France
| | - Patricia Siguier
- Laboratoire de Microbiologie et de Génétique Moléculaires (LMGM), CBI, CNRS, Université Toulouse UPS, Toulouse, France
| | - Catherine Guynet
- Laboratoire de Microbiologie et de Génétique Moléculaires (LMGM), CBI, CNRS, Université Toulouse UPS, Toulouse, France
| | - Bao Ton-Hoang
- Laboratoire de Microbiologie et de Génétique Moléculaires (LMGM), CBI, CNRS, Université Toulouse UPS, Toulouse, France
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16
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Zhang J, Liu G, Zhang X, Chang Y, Wang S, He W, Sun W, Chen D, Murchie AIH. Aminoglycoside riboswitch control of the expression of integron associated aminoglycoside resistance adenyltransferases. Virulence 2021; 11:1432-1442. [PMID: 33103573 PMCID: PMC7588185 DOI: 10.1080/21505594.2020.1836910] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022] Open
Abstract
The proliferation of antibiotic resistance has its origins in horizontal gene transfer. The class 1 integrons mediate gene transfer by assimilating antibiotic-resistance genes through site-specific recombination. For the class 1 integrons the first assimilated gene normally encodes an aminoglycoside antibiotic resistance protein which is either an aminoglycoside acetyltransferase (AAC), nucleotidyltransferase - (ANT), or adenyl transferase (AAD). An aminoglycoside-sensing riboswitch RNA in the leader RNA of AAC/AAD that controls the expression of aminoglycoside resistance genes has been previously described. Here we explore the relationship between the recombinant products of integron recombination and a series of candidate riboswitch RNAs in the 5' UTR of aad (aminoglycoside adenyltransferases) genes. The RNA sequences from the 5' UTR of the aad genes from pathogenic strains that are the products of site-specific DNA recombination by class 1 integrons were investigated. Reporter assays, MicroScale Thermophoresis (MST) and covariance analysis revealed that a functional aminoglycoside-sensing riboswitch was selected at the DNA level through integron-mediated site-specific recombination. This study explains the close association between integron recombination and the aminoglycoside-sensing riboswitch RNA.
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Affiliation(s)
- Jun Zhang
- Key Laboratory of Medical Epigenetics and Metabolism, Fudan University Pudong Medical Center, Institutes of Biomedical Sciences, Fudan University , Shanghai, PR China.,Key Laboratory of Metabolism and Molecular Medicine, Ministry of Education, School of Basic Medical Sciences, Fudan University , Shanghai, PR China
| | - Getong Liu
- Key Laboratory of Medical Epigenetics and Metabolism, Fudan University Pudong Medical Center, Institutes of Biomedical Sciences, Fudan University , Shanghai, PR China.,Key Laboratory of Metabolism and Molecular Medicine, Ministry of Education, School of Basic Medical Sciences, Fudan University , Shanghai, PR China
| | - Xuhui Zhang
- Key Laboratory of Medical Epigenetics and Metabolism, Fudan University Pudong Medical Center, Institutes of Biomedical Sciences, Fudan University , Shanghai, PR China.,Key Laboratory of Metabolism and Molecular Medicine, Ministry of Education, School of Basic Medical Sciences, Fudan University , Shanghai, PR China
| | - Yaowen Chang
- Key Laboratory of Medical Epigenetics and Metabolism, Fudan University Pudong Medical Center, Institutes of Biomedical Sciences, Fudan University , Shanghai, PR China.,Key Laboratory of Metabolism and Molecular Medicine, Ministry of Education, School of Basic Medical Sciences, Fudan University , Shanghai, PR China
| | - Shasha Wang
- Key Laboratory of Medical Epigenetics and Metabolism, Fudan University Pudong Medical Center, Institutes of Biomedical Sciences, Fudan University , Shanghai, PR China.,Key Laboratory of Metabolism and Molecular Medicine, Ministry of Education, School of Basic Medical Sciences, Fudan University , Shanghai, PR China
| | - Weizhi He
- Key Laboratory of Medical Epigenetics and Metabolism, Fudan University Pudong Medical Center, Institutes of Biomedical Sciences, Fudan University , Shanghai, PR China.,Key Laboratory of Metabolism and Molecular Medicine, Ministry of Education, School of Basic Medical Sciences, Fudan University , Shanghai, PR China
| | - Wenxia Sun
- Key Laboratory of Medical Epigenetics and Metabolism, Fudan University Pudong Medical Center, Institutes of Biomedical Sciences, Fudan University , Shanghai, PR China.,Key Laboratory of Metabolism and Molecular Medicine, Ministry of Education, School of Basic Medical Sciences, Fudan University , Shanghai, PR China
| | - Dongrong Chen
- Key Laboratory of Medical Epigenetics and Metabolism, Fudan University Pudong Medical Center, Institutes of Biomedical Sciences, Fudan University , Shanghai, PR China.,Key Laboratory of Metabolism and Molecular Medicine, Ministry of Education, School of Basic Medical Sciences, Fudan University , Shanghai, PR China
| | - Alastair I H Murchie
- Key Laboratory of Medical Epigenetics and Metabolism, Fudan University Pudong Medical Center, Institutes of Biomedical Sciences, Fudan University , Shanghai, PR China.,Key Laboratory of Metabolism and Molecular Medicine, Ministry of Education, School of Basic Medical Sciences, Fudan University , Shanghai, PR China
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17
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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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18
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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: 6] [Impact Index Per Article: 1.5] [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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19
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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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20
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The Peril and Promise of Integrons: Beyond Antibiotic Resistance. Trends Microbiol 2020; 28:455-464. [PMID: 31948729 DOI: 10.1016/j.tim.2019.12.002] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2019] [Revised: 11/13/2019] [Accepted: 12/09/2019] [Indexed: 12/11/2022]
Abstract
Integrons are bacterial genetic elements that can capture, rearrange, and express mobile gene cassettes. They are best known for their role in disseminating antibiotic-resistance genes among pathogens. Their ability to rapidly spread resistance phenotypes makes it important to consider what other integron-mediated traits might impact human health in the future, such as increased virulence, pathogenicity, or resistance to novel antimicrobial strategies. Exploring the functional diversity of cassettes and understanding their de novo creation will allow better pre-emptive management of bacterial growth, while also facilitating development of technologies that could harness integron activity. If we can control integrons and cassette formation, we could use integrons as a platform for enzyme discovery and to construct novel biochemical pathways, with applications in bioremediation or biosynthesis of industrial and therapeutic molecules. Integron activity thus holds both peril and promise for humans.
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21
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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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22
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Xiao L, Wang X, Kong N, Cao M, Zhang L, Wei Q, Liu W. Polymorphisms of Gene Cassette Promoters of the Class 1 Integron in Clinical Proteus Isolates. Front Microbiol 2019; 10:790. [PMID: 31068909 PMCID: PMC6491665 DOI: 10.3389/fmicb.2019.00790] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2018] [Accepted: 03/27/2019] [Indexed: 11/21/2022] Open
Abstract
OBJECTIVE To describe the polymorphisms of gene cassette promoters of the class 1 integron in clinical Proteus isolates and their relationship with antibiotic resistance. METHODS Polymorphisms of the gene cassette promoter in 153 strains of Proteus were analyzed by PCR and nucleotide sequencing. Variable regions of atypical class 1 integrons were detected by inverse PCR and nucleotide sequencing. Enterobacterial repetitive intergenic consensus (ERIC)-PCR was used to analyze the phylogenetic relationships of class 1 integron-positive clinical Proteus isolates. Representative beta-lactamase genes (bla), including bla TEM,bla SHV,bla CTX-M-1,bla CTX-M-2,bla CTX-M-8,bla CTX-M-9,bla CTX-M-25 and bla OXA-1, and plasmid-mediated quinolone resistance (PMQR) genes including qnrA, qnrB, qnrC, qnrD, qnrS, oqxA, oqxB, qepA, and aac(6')-Ib were also screened using PCR and sequence analysis. RESULTS Fifteen different gene cassette arrays and 20 different gene cassettes were detected in integron-positive strains. Of them, aadB-aadA2 (37/96) was the most common gene cassette array. Two of these gene cassette arrays (estX-psp-aadA2-cmlA1, estX-psp-aadA2-cmlA1-aadA1a-qacI-tnpA-sul3) have not previously been reported. Three different Pc-P2 variants (PcS, PcWTGN-10, PcH1) were detected among the 96 Proteus strains, with PcH1 being the most common (49/96). Strains carrying the promoters PcS or PcWTGN-10 were more resistant to sulfamethoxazole, gentamicin and tobramycin than those carrying PcH1. Strains with weak promoter (PcH1) harbored significantly more intra- and extra-integron antibiotic resistance genes than isolates with strong promoter (PcWTGN-10). Further, among 153 isolates, representative beta-lactamase genes were detected in 70 isolates (bla TEM-1, 54; bla OXA-1, 40; bla CTX-M-3, 12; bla CTX-M-14, 12; bla CTX-M-65, 5; bla CTX-M-15, 2) and representative PMQR genes were detected in 87 isolates (qnrA, 6; qnrB, 3; qnrC, 5; qnrD, 46; qnrS, 5; oqxA, 7; aac(6')-Ib, 13; aac(6')-Ib-cr, 32). CONCLUSION To the best of our knowledge, this study provides the first evidence for polymorphisms of the class 1 integron variable promoter in clinical Proteus isolates, which generally contain relatively strong promoters. Resistance genotypes showed a higher coincidence rate with the drug-resistant phenotype in strong-promoter-containing strains, resulting in an ability to confer strong resistance to antibiotics among host bacteria and a relatively limited ability to capture gene cassettes. Moreover, strains with relatively weak integron promoters can "afford" a heavier "extra-integron antibiotic resistance gene load". Furthermore, the gene cassettes estX, psp and the gene cassette arrays estX-psp-aadA2-cmlA1, estX-psp-aadA2-cmlA1-aadA1a-qacI-tnpA-sul3 have been confirmed for the first time in clinical Proteus isolates. Beta-lactamase genes and PMQR were investigated, and bla TEM-1 and bla OXA-1 were the most common, with qnrD and aac (6')-Ib-cr also being dominant.
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Affiliation(s)
- Linlin Xiao
- Shanghai University of Medicine & Health Sciences Affiliated Sixth People's Hospital South Campus, Shanghai, China
- Department of Laboratory Medicine, Affiliated Sixth People's Hospital South Campus, Shanghai Jiaotong University, Shanghai, China
- Department of Laboratory Medicine, Shanghai Tenth People's Hospital, Tongji University, Shanghai, China
| | - Xiaotong Wang
- Anhui University of Science and Technology, Anhui, China
| | - Nana Kong
- Anhui University of Science and Technology, Anhui, China
| | - Mei Cao
- Anhui University of Science and Technology, Anhui, China
| | - Long Zhang
- Anhui University of Science and Technology, Anhui, China
| | - Quhao Wei
- Shanghai University of Medicine & Health Sciences Affiliated Sixth People's Hospital South Campus, Shanghai, China
- Department of Laboratory Medicine, Affiliated Sixth People's Hospital South Campus, Shanghai Jiaotong University, Shanghai, China
- Anhui University of Science and Technology, Anhui, China
- Centre of Laboratory Medicine, Zhejiang Provincial People's Hospital, Hangzhou, China
| | - Weiwei Liu
- Department of Laboratory Medicine, Shanghai Tenth People's Hospital, Tongji University, Shanghai, China
- Department of Laboratory Medicine, Shanghai Skin Disease Hospital, Tongji University, Shanghai, China
- Department of Laboratory Medicine, Shanghai First People's Hospital, Shanghai Jiaotong University, Shanghai, China
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23
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Bastedo DP, Lo T, Laflamme B, Desveaux D, Guttman DS. Diversity and Evolution of Type III Secreted Effectors: A Case Study of Three Families. Curr Top Microbiol Immunol 2019; 427:201-230. [DOI: 10.1007/82_2019_165] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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24
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Erkes A, Reschke M, Boch J, Grau J. Evolution of Transcription Activator-Like Effectors in Xanthomonas oryzae. Genome Biol Evol 2018. [PMID: 28637323 PMCID: PMC5512977 DOI: 10.1093/gbe/evx108] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Transcription activator-like effectors (TALEs) are secreted by plant–pathogenic Xanthomonas bacteria into plant cells where they act as transcriptional activators and, hence, are major drivers in reprogramming the plant for the benefit of the pathogen. TALEs possess a highly repetitive DNA-binding domain of typically 34 amino acid (AA) tandem repeats, where AA 12 and 13, termed repeat variable di-residue (RVD), determine target specificity. Different Xanthomonas strains possess different repertoires of TALEs. Here, we study the evolution of TALEs from the level of RVDs determining target specificity down to the level of DNA sequence with focus on rice-pathogenic Xanthomonas oryzae pv. oryzae (Xoo) and Xanthomonas oryzae pv. oryzicola (Xoc) strains. We observe that codon pairs coding for individual RVDs are conserved to a similar degree as the flanking repeat sequence. We find strong indications that TALEs may evolve 1) by base substitutions in codon pairs coding for RVDs, 2) by recombination of N-terminal or C-terminal regions of existing TALEs, or 3) by deletion of individual TALE repeats, and we propose possible mechanisms. We find indications that the reassortment of TALE genes in clusters is mediated by an integron-like mechanism in Xoc. We finally study the effect of the presence/absence and evolutionary modifications of TALEs on transcriptional activation of putative target genes in rice, and find that even single RVD swaps may lead to considerable differences in activation. This correlation allowed a refined prediction of TALE targets, which is the crucial step to decipher their virulence activity.
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Affiliation(s)
- Annett Erkes
- Institute of Computer Science, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
| | - Maik Reschke
- Department of Plant Biotechnology, Leibniz Universität Hannover, Germany
| | - Jens Boch
- Department of Plant Biotechnology, Leibniz Universität Hannover, Germany
| | - Jan Grau
- Institute of Computer Science, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
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25
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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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26
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Wang D, Hou W, Chen J, Yang L, Liu Z, Yin Z, Feng J, Zhou D. Characterization of Novel Integrons, In 1085 and In 1086, and the Surrounding Genes in Plasmids from Enterobacteriaceae, and the Role for attCaadA16 Structural Features during attI1 × attC Integration. Front Microbiol 2017. [PMID: 28626457 PMCID: PMC5454043 DOI: 10.3389/fmicb.2017.01003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
Novel class 1 integrons In1085 and In1086, containing the class D β-lactamase -encoding gene blaOXA, were identified in clinical enterobacterial strains. In this study, we aimed to characterize the genetic contexts of In1085 and In1086, with the goal of identifying putative mechanisms of integron mobilization. Four plasmids, approximately 5.3, 5.3, 5.7, and 6.6 kb, from 71 clinical Enterobacteriaceae strains were found to contain class 1 integrons (In37, In62, In1085, and In1086, respectively). Two of these plasmids, pEco336 and pNsa292, containing In1085 and In1086, respectively, were further characterized by antibiotic susceptibility testing, conjugation experiments, PCR, sequencing, and gene mapping. The OXA-type carbapenemase activities of the parental strains were also assessed. The results revealed that the novel integrons had different genetic environments, and therefore demonstrated diverse biochemical characteristics. Using evolutionary inferences based on the recombination of gene cassettes, we also identified a role for attCaadA16 structural features during attI1 × attC insertion reactions. Our analysis showed that gene cassette insertions in the bottom strand of attCaadA16 in the correct orientation lead to the expression the encoded genes from the Pc promoter. Our study suggests that the genetic features harbored within the integrons are inserted in a discernable pattern, involving the stepwise and parallel evolution of class 1 integron variations under antibiotic selection pressures in a clinical setting.
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Affiliation(s)
- Dongguo Wang
- Department of Clinical Laboratory Medicine, Taizhou Municipal Hospital Affiliated with Taizhou University and the Institute of Molecular Diagnostics of Taizhou UniversityTaizhou, China
| | - Wei Hou
- Department of Infection, Taizhou Municipal Hospital Affiliated with Taizhou UniversityTaizhou, China
| | - Jiayu Chen
- Basic Department, Shaoxing UniversityTaizhou, China
| | - Linjun Yang
- Department of the Thyroid Gland and Breast Surgery, Taizhou Municipal Hospital Affiliated with Taizhou UniversityTaizhou, China
| | - Zhihui Liu
- Department of Stomatology, Taizhou Municipal Hospital Affiliated with the Medical College of Taizhou UniversityTaizhou, China
| | - Zhe Yin
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and EpidemiologyBeijing, China
| | - Jiao Feng
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and EpidemiologyBeijing, China
| | - Dongsheng Zhou
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and EpidemiologyBeijing, China
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27
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Differences in Integron Cassette Excision Dynamics Shape a Trade-Off between Evolvability and Genetic Capacitance. mBio 2017; 8:mBio.02296-16. [PMID: 28351923 PMCID: PMC5371416 DOI: 10.1128/mbio.02296-16] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Integrons ensure a rapid and "on demand" response to environmental stresses driving bacterial adaptation. They are able to capture, store, and reorder functional gene cassettes due to site-specific recombination catalyzed by their integrase. Integrons can be either sedentary and chromosomally located or mobile when they are associated with transposons and plasmids. They are respectively called sedentary chromosomal integrons (SCIs) and mobile integrons (MIs). MIs are key players in the dissemination of antibiotic resistance genes. Here, we used in silico and in vivo approaches to study cassette excision dynamics in MIs and SCIs. We show that the orientation of cassette arrays relative to replication influences attC site folding and cassette excision by placing the recombinogenic strands of attC sites on either the leading or lagging strand template. We also demonstrate that stability of attC sites and their propensity to form recombinogenic structures also regulate cassette excision. We observe that cassette excision dynamics driven by these factors differ between MIs and SCIs. Cassettes with high excision rates are more commonly found on MIs, which favors their dissemination relative to SCIs. This is especially true for SCIs carried in the Vibrio genus, where maintenance of large cassette arrays and vertical transmission are crucial to serve as a reservoir of adaptive functions. These results expand the repertoire of known processes regulating integron recombination that were previously established and demonstrate that, in terms of cassette dynamics, a subtle trade-off between evolvability and genetic capacitance has been established in bacteria.IMPORTANCE The integron system confers upon bacteria a rapid adaptation capability in changing environments. Specifically, integrons are involved in the continuous emergence of bacteria resistant to almost all antibiotic treatments. The international situation is critical, and in 2050, the annual number of deaths caused by multiresistant bacteria could reach 10 million, exceeding the incidence of deaths related to cancer. It is crucial to increase our understanding of antibiotic resistance dissemination and therefore integron recombination dynamics to find new approaches to cope with the worldwide problem of multiresistance. Here, we studied the dynamics of recombination and dissemination of gene encoding cassettes carried on integrons. By combining in silico and in vivo analyses, we show that cassette excision is highly regulated by replication and by the intrinsic properties of cassette recombination sites. We also demonstrated differences in the dynamics of cassette recombination between mobile and sedentary chromosomal integrons (MIs and SCIs). For MIs, a high cassette recombination rate is favored and timed to conditions when generating diversity (upon which selection can act) allows for a rapid response to environmental conditions and stresses. In contrast, for SCIs, cassette excisions are less frequent, limiting cassette loss and ensuring a large pool of cassettes. We therefore confirm a role of SCIs as reservoirs of adaptive functions and demonstrate that the remarkable adaptive success of integron recombination system is due to its intricate regulation.
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