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Ardissone S, Greub G. The Chlamydia-related Waddlia chondrophila encodes functional type II toxin-antitoxin systems. Appl Environ Microbiol 2024; 90:e0068123. [PMID: 38214519 PMCID: PMC10880633 DOI: 10.1128/aem.00681-23] [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: 04/25/2023] [Accepted: 11/13/2023] [Indexed: 01/13/2024] Open
Abstract
Bacterial toxin-antitoxin (TA) systems are widespread in chromosomes and plasmids of free-living microorganisms, but only a few have been identified in obligate intracellular species. We found seven putative type II TA modules in Waddlia chondrophila, a Chlamydia-related species that is able to infect a very broad series of eukaryotic hosts, ranging from protists to mammalian cells. The RNA levels of Waddlia TA systems are significantly upregulated by iron starvation and novobiocin, but they are not affected by antibiotics such as β-lactams and glycopeptides, which suggests different mechanisms underlying stress responses. Five of the identified TA modules, including HigBA1 and MazEF1, encoded on the Waddlia cryptic plasmid, proved to be functional when expressed in a heterologous host. TA systems have been associated with the maintenance of mobile genetic elements, bacterial defense against bacteriophages, and persistence upon exposure to adverse conditions. As their RNA levels are upregulated upon exposure to adverse conditions, Waddlia TA modules may be involved in survival to stress. Moreover, as Waddlia can infect a wide range of hosts including free-living amoebae, TA modules could also represent an innate immunity system to fight against bacteriophages and other microorganisms with which Waddlia has to share its replicative niche.IMPORTANCEThe response to adverse conditions, such as exposure to antibiotics, nutrient starvation and competition with other microorganisms, is essential for the survival of a bacterial population. TA systems are modules composed of two elements, a toxic protein and an antitoxin (protein or RNA) that counteracts the toxin. Although many aspects of TA biological functions still await to be elucidated, TAs have often been implicated in bacterial response to stress, including the response to nutrient starvation, antibiotic treatment and bacteriophage infection. TAs are ubiquitous in free-living bacteria but rare in obligate intracellular species such as chlamydiae. We identified functional TA systems in Waddlia chondrophila, a chlamydial species with a strikingly broad host range compared to other chlamydiae. Our work contributes to understand how obligate intracellular bacteria react to adverse conditions that might arise from competition with other viruses/bacteria for the same replicative niche and would threaten their ability to replicate.
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Affiliation(s)
- Silvia Ardissone
- Institute of Microbiology, Lausanne University Hospital and Lausanne University, Lausanne, Switzerland
| | - Gilbert Greub
- Institute of Microbiology, Lausanne University Hospital and Lausanne University, Lausanne, Switzerland
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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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Garcia-Rodriguez G, Girardin Y, Kumar Singh R, Volkov AN, Van Dyck J, Muruganandam G, Sobott F, Charlier D, Loris R. Toxin:antitoxin ratio sensing autoregulation of the Vibrio cholerae parDE2 module. SCIENCE ADVANCES 2024; 10:eadj2403. [PMID: 38181072 PMCID: PMC10776004 DOI: 10.1126/sciadv.adj2403] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2023] [Accepted: 12/04/2023] [Indexed: 01/07/2024]
Abstract
The parDE family of toxin-antitoxin (TA) operons is ubiquitous in bacterial genomes and, in Vibrio cholerae, is an essential component to maintain the presence of chromosome II. Here, we show that transcription of the V. cholerae parDE2 (VcparDE) operon is regulated in a toxin:antitoxin ratio-dependent manner using a molecular mechanism distinct from other type II TA systems. The repressor of the operon is identified as an assembly with a 6:2 stoichiometry with three interacting ParD2 dimers bridged by two ParE2 monomers. This assembly docks to a three-site operator containing 5'- GGTA-3' motifs. Saturation of this TA complex with ParE2 toxin results in disruption of the interface between ParD2 dimers and the formation of a TA complex of 2:2 stoichiometry. The latter is operator binding-incompetent as it is incompatible with the required spacing of the ParD2 dimers on the operator.
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Affiliation(s)
- Gabriela Garcia-Rodriguez
- Structural Biology Brussels, Department of Biotechnology, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussel, Belgium
- Structural Biology Research Center, Vlaams Instituut voor Biotechnologie, Pleinlaan 2, B-1050 Brussel, Belgium
| | - Yana Girardin
- Structural Biology Brussels, Department of Biotechnology, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussel, Belgium
- Structural Biology Research Center, Vlaams Instituut voor Biotechnologie, Pleinlaan 2, B-1050 Brussel, Belgium
| | - Ranjan Kumar Singh
- Structural Biology Brussels, Department of Biotechnology, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussel, Belgium
- Structural Biology Research Center, Vlaams Instituut voor Biotechnologie, Pleinlaan 2, B-1050 Brussel, Belgium
| | - Alexander N. Volkov
- Structural Biology Brussels, Department of Biotechnology, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussel, Belgium
- Structural Biology Research Center, Vlaams Instituut voor Biotechnologie, Pleinlaan 2, B-1050 Brussel, Belgium
- Jean Jeener NMR Centre, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussel, Belgium
| | - Jeroen Van Dyck
- Department of Chemistry, Universiteit Antwerpen, Groenenborgerlaan 171, Antwerpen 2020, Belgium
| | - Gopinath Muruganandam
- Structural Biology Brussels, Department of Biotechnology, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussel, Belgium
- Structural Biology Research Center, Vlaams Instituut voor Biotechnologie, Pleinlaan 2, B-1050 Brussel, Belgium
| | - Frank Sobott
- Astbury Centre for Structural Molecular Biology and School of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT, UK
| | - Daniel Charlier
- Research Group of Microbiology, Department of Bioengineering Sciences, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussel, Belgium
| | - Remy Loris
- Structural Biology Brussels, Department of Biotechnology, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussel, Belgium
- Structural Biology Research Center, Vlaams Instituut voor Biotechnologie, Pleinlaan 2, B-1050 Brussel, Belgium
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4
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Lin JD, Stogios PJ, Abe KT, Wang A, MacPherson J, Skarina T, Gingras AC, Savchenko A, Ensminger AW. Functional diversification despite structural congruence in the HipBST toxin-antitoxin system of Legionella pneumophila. mBio 2023; 14:e0151023. [PMID: 37819088 PMCID: PMC10653801 DOI: 10.1128/mbio.01510-23] [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: 06/16/2023] [Accepted: 08/29/2023] [Indexed: 10/13/2023] Open
Abstract
IMPORTANCE Toxin-antitoxin (TA) systems are parasitic genetic elements found in almost all bacterial genomes. They are exchanged horizontally between cells and are typically poorly conserved across closely related strains and species. Here, we report the characterization of a tripartite TA system in the bacterial pathogen Legionella pneumophila that is highly conserved across Legionella species genomes. This system (denoted HipBSTLp) is a distant homolog of the recently discovered split-HipA system in Escherichia coli (HipBSTEc). We present bioinformatic, molecular, and structural analyses of the divergence between these two systems and the functionality of this newly described TA system family. Furthermore, we provide evidence to refute previous claims that the toxin in this system (HipTLp) possesses bifunctionality as an L. pneumophila virulence protein. Overall, this work expands our understanding of the split-HipA system architecture and illustrates the potential for undiscovered biology in these abundant genetic elements.
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Affiliation(s)
- Jordan D. Lin
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - Peter J. Stogios
- Department of Chemical Engineering and Applied Chemistry, University of Toronto, Toronto, Ontario, Canada
| | - Kento T. Abe
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
- Lunenfeld-Tanenbaum Research Institute, Sinai Health, Toronto, Ontario, Canada
| | - Avril Wang
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - John MacPherson
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - Tatiana Skarina
- Department of Chemical Engineering and Applied Chemistry, University of Toronto, Toronto, Ontario, Canada
| | - Anne-Claude Gingras
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
- Lunenfeld-Tanenbaum Research Institute, Sinai Health, Toronto, Ontario, Canada
| | - Alexei Savchenko
- Department of Chemical Engineering and Applied Chemistry, University of Toronto, Toronto, Ontario, Canada
- Department of Microbiology, Immunology and Infectious Diseases, University of Calgary, Calgary, Alberta, Canada
- Center for Structural Genomics of Infectious Diseases (CSGID), University of Calgary, Calgary, Alberta, Canada
| | - Alexander W. Ensminger
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
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5
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Hsueh BY, Ferrell MJ, Sanath-Kumar R, Bedore AM, Waters CM. Replication cycle timing determines phage sensitivity to a cytidine deaminase toxin/antitoxin bacterial defense system. PLoS Pathog 2023; 19:e1011195. [PMID: 37683045 PMCID: PMC10511110 DOI: 10.1371/journal.ppat.1011195] [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: 02/09/2023] [Revised: 09/20/2023] [Accepted: 07/21/2023] [Indexed: 09/10/2023] Open
Abstract
Toxin-antitoxin (TA) systems are ubiquitous two-gene loci that bacteria use to regulate cellular processes such as phage defense. Here, we demonstrate the mechanism by which a novel type III TA system, avcID, is activated and confers resistance to phage infection. The toxin of the system (AvcD) is a deoxycytidylate deaminase that converts deoxycytidines (dC) to dexoyuridines (dU), while the RNA antitoxin (AvcI) inhibits AvcD activity. We have shown that AvcD deaminated dC nucleotides upon phage infection, but the molecular mechanism that activated AvcD was unknown. Here we show that the activation of AvcD arises from phage-induced inhibition of host transcription, leading to degradation of the labile AvcI. AvcD activation and nucleotide depletion not only decreases phage replication but also increases the formation of defective phage virions. Surprisingly, infection of phages such as T7 that are not inhibited by AvcID also lead to AvcI RNA antitoxin degradation and AvcD activation, suggesting that depletion of AvcI is not sufficient to confer protection against some phage. Rather, our results support that phage with a longer replication cycle like T5 are sensitive to AvcID-mediated protection while those with a shorter replication cycle like T7 are resistant.
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Affiliation(s)
- Brian Y. Hsueh
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, United States of America
| | - Micah J. Ferrell
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, United States of America
| | - Ram Sanath-Kumar
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, United States of America
| | - Amber M. Bedore
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, United States of America
| | - Christopher M. Waters
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, United States of America
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6
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Hsueh BY, Sanath-Kumar R, Bedore AM, Waters CM. Time to lysis determines phage sensitivity to a cytidine deaminase toxin/antitoxin bacterial defense system. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.02.09.527960. [PMID: 36798279 PMCID: PMC9934689 DOI: 10.1101/2023.02.09.527960] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
Toxin-antitoxin (TA) systems are ubiquitous two-gene loci that bacteria use to regulate cellular processes such as phage defense. Here, we demonstrate the mechanism by which a novel type III TA system, avcID , is activated and confers resistance to phage infection. The toxin of the system (AvcD) is a deoxycytidylate deaminase that converts deoxycytidines (dC) to dexoyuridines (dU), while the RNA antitoxin (AvcI) inhibits AvcD activity. We have shown that AvcD deaminated dC nucleotides upon phage infection, but the molecular mechanism that activated AvcD was unknown. Here we show that the activation of AvcD arises from phage-induced shutoff of host transcription, leading to degradation of the labile AvcI. AvcD activation and nucleotide depletion not only decreases phage replication but also increases the formation of defective phage virions. Surprisingly, infection of phages such as T7 that are not inhibited by AvcID also lead to AvcI RNA antitoxin degradation and AvcD activation, suggesting that depletion of AvcI is not sufficient to confer protection against some phage. Rather, our results support that phage with a longer lysis time like T5 are sensitive to AvcID-mediated protection while those with a shorter lysis time like T7 are resistant. AUTHOR’S SUMMARY Numerous diverse antiphage defense systems have been discovered in the past several years, but the mechanisms of how these systems are activated upon phage infection and why these systems protect against some phage but not others are poorly understood. The AvcID toxin-antitoxin phage defense system depletes nucleotides of the dC pool inside the host upon phage infection. We show that phage inhibition of host cell transcription activates this system by depleting the AvcI inhibitory sRNA, which inhibits production of phage and leads to the formation of defective virions. Additionally, we determined that phage lysis time is a key factor that influences sensitivity to AvcID with faster replicating phage exhibiting resistance to its effects. This study has implications for understanding the factors that influence bacterial host/phage dynamics.
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Affiliation(s)
- Brian Y. Hsueh
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, USA, 48824
| | - Ram Sanath-Kumar
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, USA, 48824
| | - Amber M. Bedore
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, USA, 48824
| | - Christopher M. Waters
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, USA, 48824
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7
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Krin E, Baharoglu Z, Sismeiro O, Varet H, Coppée JY, Mazel D. Systematic transcriptome analysis allows the identification of new type I and type II Toxin/Antitoxin systems located in the superintegron of Vibrio cholerae. Res Microbiol 2023; 174:103997. [PMID: 36347445 DOI: 10.1016/j.resmic.2022.103997] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2022] [Revised: 10/27/2022] [Accepted: 10/28/2022] [Indexed: 11/07/2022]
Abstract
Vibrio cholerae N16961 genome encodes 18 type II Toxin/Antitoxin (TA) systems, all but one located inside gene cassettes of its chromosomal superintegron (SI). This study aims to investigate additional TA systems in this genome. We screened for all two-genes operons of uncharacterized function by analyzing previous RNAseq data. Assays on nine candidates, revealed one additional functional type II TA encoded by the VCA0497-0498 operon, carried inside a SI cassette. We showed that VCA0498 antitoxin alone and in complex with VCA0497 represses its own operon promoter. VCA0497-0498 is the second element of the recently identified dhiT/dhiA superfamily uncharacterized type II TA system. RNAseq analysis revealed that another SI cassette encodes a novel type I TA system: VCA0495 gene and its two associated antisense non-coding RNAs, ncRNA495 and ncRNA496. Silencing of both antisense ncRNAs lead to cell death, demonstrating the type I TA function. Both VCA0497 and VCA0495 toxins do not show any homology to functionally characterized toxins, however our preliminary data suggest that their activity may end up in mRNA degradation, directly or indirectly. Our findings increase the TA systems number carried in this SI to 19, preferentially located in its distal end, confirming their importance in this large cassette array.
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Affiliation(s)
- Evelyne Krin
- Institut Pasteur, Université Paris Cité, CNRS UMR 3525, Unité de Plasticité du Génome Bactérien, 28 rue du Docteur Roux, F-75015 Paris, France.
| | - Zeynep Baharoglu
- Institut Pasteur, Université Paris Cité, CNRS UMR 3525, Unité de Plasticité du Génome Bactérien, 28 rue du Docteur Roux, F-75015 Paris, France.
| | - Odile Sismeiro
- Institut Pasteur, Université Paris Cité, Transcriptome and EpiGenome, Biomics Center for Innovation and Technological Research, 28 rue du Docteur Roux, F-75015 Paris, France.
| | - Hugo Varet
- Institut Pasteur, Université Paris Cité, Transcriptome and EpiGenome, Biomics Center for Innovation and Technological Research, 28 rue du Docteur Roux, F-75015 Paris, France.
| | - Jean-Yves Coppée
- Institut Pasteur, Université Paris Cité, Transcriptome and EpiGenome, Biomics Center for Innovation and Technological Research, 28 rue du Docteur Roux, F-75015 Paris, France.
| | - Didier Mazel
- Institut Pasteur, Université Paris Cité, CNRS UMR 3525, Unité de Plasticité du Génome Bactérien, 28 rue du Docteur Roux, F-75015 Paris, France.
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8
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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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9
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Ferrarini MG, Dell’Aglio E, Vallier A, Balmand S, Vincent-Monégat C, Hughes S, Gillet B, Parisot N, Zaidman-Rémy A, Vieira C, Heddi A, Rebollo R. Efficient compartmentalization in insect bacteriomes protects symbiotic bacteria from host immune system. MICROBIOME 2022; 10:156. [PMID: 36163269 PMCID: PMC9513942 DOI: 10.1186/s40168-022-01334-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/02/2022] [Accepted: 07/25/2022] [Indexed: 06/16/2023]
Abstract
BACKGROUND Many insects house symbiotic intracellular bacteria (endosymbionts) that provide them with essential nutrients, thus promoting the usage of nutrient-poor habitats. Endosymbiont seclusion within host specialized cells, called bacteriocytes, often organized in a dedicated organ, the bacteriome, is crucial in protecting them from host immune defenses while avoiding chronic host immune activation. Previous evidence obtained in the cereal weevil Sitophilus oryzae has shown that bacteriome immunity is activated against invading pathogens, suggesting endosymbionts might be targeted and impacted by immune effectors during an immune challenge. To pinpoint any molecular determinants associated with such challenges, we conducted a dual transcriptomic analysis of S. oryzae's bacteriome subjected to immunogenic peptidoglycan fragments. RESULTS We show that upon immune challenge, the bacteriome actively participates in the innate immune response via induction of antimicrobial peptides (AMPs). Surprisingly, endosymbionts do not undergo any transcriptomic changes, indicating that this potential threat goes unnoticed. Immunohistochemistry showed that TCT-induced AMPs are located outside the bacteriome, excluding direct contact with the endosymbionts. CONCLUSIONS This work demonstrates that endosymbiont protection during an immune challenge is mainly achieved by efficient confinement within bacteriomes, which provides physical separation between host systemic response and endosymbionts. Video Abstract.
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Affiliation(s)
- Mariana Galvão Ferrarini
- Univ Lyon, INRAE, INSA-Lyon, BF2I, UMR 203, 69621 Villeurbanne, France
- Laboratoire de Biométrie et Biologie Evolutive, UMR5558, Université Lyon 1, Université Lyon, Villeurbanne, France
| | - Elisa Dell’Aglio
- Univ Lyon, INRAE, INSA-Lyon, BF2I, UMR 203, 69621 Villeurbanne, France
| | - Agnès Vallier
- Univ Lyon, INRAE, INSA-Lyon, BF2I, UMR 203, 69621 Villeurbanne, France
| | - Séverine Balmand
- Univ Lyon, INRAE, INSA-Lyon, BF2I, UMR 203, 69621 Villeurbanne, France
| | | | - Sandrine Hughes
- UMR5242, Institut de Génomique Fonctionnelle de Lyon (IGFL), Ecole Normale Supérieure de Lyon, Centre National de la Recherche Scientifique (CNRS), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon (Univ Lyon), F-69007 Lyon, France
| | - Benjamin Gillet
- UMR5242, Institut de Génomique Fonctionnelle de Lyon (IGFL), Ecole Normale Supérieure de Lyon, Centre National de la Recherche Scientifique (CNRS), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon (Univ Lyon), F-69007 Lyon, France
| | - Nicolas Parisot
- Univ Lyon, INSA-Lyon, INRAE, BF2I, UMR 203, 69621 Villeurbanne, France
| | - Anna Zaidman-Rémy
- Univ Lyon, INSA-Lyon, INRAE, BF2I, UMR 203, 69621 Villeurbanne, France
| | - Cristina Vieira
- Laboratoire de Biométrie et Biologie Evolutive, UMR5558, Université Lyon 1, Université Lyon, Villeurbanne, France
| | - Abdelaziz Heddi
- Univ Lyon, INSA-Lyon, INRAE, BF2I, UMR 203, 69621 Villeurbanne, France
| | - Rita Rebollo
- Univ Lyon, INRAE, INSA-Lyon, BF2I, UMR 203, 69621 Villeurbanne, France
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10
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Martinez J, Ant TH, Murdochy SM, Tong L, da Silva Filipe A, Sinkins SP. Genome sequencing and comparative analysis of Wolbachia strain wAlbA reveals Wolbachia-associated plasmids are common. PLoS Genet 2022; 18:e1010406. [PMID: 36121852 PMCID: PMC9560607 DOI: 10.1371/journal.pgen.1010406] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2022] [Revised: 10/13/2022] [Accepted: 09/02/2022] [Indexed: 11/18/2022] Open
Abstract
Wolbachia are widespread maternally-transmitted bacteria of arthropods that often spread by manipulating their host's reproduction through cytoplasmic incompatibility (CI). Their invasive potential is currently being harnessed in field trials aiming to control mosquito-borne diseases. Wolbachia genomes commonly harbour prophage regions encoding the cif genes which confer their ability to induce CI. Recently, a plasmid-like element was discovered in wPip, a Wolbachia strain infecting Culex mosquitoes; however, it is unclear how common such extra-chromosomal elements are in Wolbachia. Here we sequenced the complete genome of wAlbA, a strain of the symbiont found in Aedes albopictus, after eliminating the co-infecting and higher density wAlbB strain that previously made sequencing of wAlbA challenging. We show that wAlbA is associated with two new plasmids and identified additional Wolbachia plasmids and related chromosomal islands in over 20% of publicly available Wolbachia genome datasets. These plasmids encode a variety of accessory genes, including several phage-like DNA packaging genes as well as genes potentially contributing to host-symbiont interactions. In particular, we recovered divergent homologues of the cif genes in both Wolbachia- and Rickettsia-associated plasmids. Our results indicate that plasmids are common in Wolbachia and raise fundamental questions around their role in symbiosis. In addition, our comparative analysis provides useful information for the future development of genetic tools to manipulate and study Wolbachia symbionts.
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Affiliation(s)
- Julien Martinez
- MRC-University of Glasgow Centre for Virus Research, Glasgow, United Kingdom
| | - Thomas H. Ant
- MRC-University of Glasgow Centre for Virus Research, Glasgow, United Kingdom
| | - Shivan M. Murdochy
- MRC-University of Glasgow Centre for Virus Research, Glasgow, United Kingdom
| | - Lily Tong
- MRC-University of Glasgow Centre for Virus Research, Glasgow, United Kingdom
| | - Ana da Silva Filipe
- MRC-University of Glasgow Centre for Virus Research, Glasgow, United Kingdom
| | - Steven P. Sinkins
- MRC-University of Glasgow Centre for Virus Research, Glasgow, United Kingdom
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11
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Dai Z, Wu T, Xu S, Zhou L, Tang W, Hu E, Zhan L, Chen M, Yu G. Characterization of toxin-antitoxin systems from public sequencing data: A case study in Pseudomonas aeruginosa. Front Microbiol 2022; 13:951774. [PMID: 36051757 PMCID: PMC9424990 DOI: 10.3389/fmicb.2022.951774] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2022] [Accepted: 07/15/2022] [Indexed: 11/13/2022] Open
Abstract
The toxin-antitoxin (TA) system is a widely distributed group of genetic modules that play important roles in the life of prokaryotes, with mobile genetic elements (MGEs) contributing to the dissemination of antibiotic resistance gene (ARG). The diversity and richness of TA systems in Pseudomonas aeruginosa, as one of the bacterial species with ARGs, have not yet been completely demonstrated. In this study, we explored the TA systems from the public genomic sequencing data and genome sequences. A small scale of genomic sequencing data in 281 isolates was selected from the NCBI SRA database, reassembling the genomes of these isolates led to the findings of abundant TA homologs. Furthermore, remapping these identified TA modules on 5,437 genome/draft genomes uncovers a great diversity of TA modules in P. aeruginosa. Moreover, manual inspection revealed several TA systems that were not yet reported in P. aeruginosa including the hok-sok, cptA-cptB, cbeA-cbtA, tomB-hha, and ryeA-sdsR. Additional annotation revealed that a large number of MGEs were closely distributed with TA. Also, 16% of ARGs are located relatively close to TA. Our work confirmed a wealth of TA genes in the unexplored P. aeruginosa pan-genomes, expanded the knowledge on P. aeruginosa, and provided methodological tips on large-scale data mining for future studies. The co-occurrence of MGE, ARG, and TA may indicate a potential interaction in their dissemination.
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12
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Song X, Lin Z, Yuan W. Toxin-antitoxin systems in pathogenic Vibrio species: a mini review from a structure perspective. 3 Biotech 2022; 12:125. [PMID: 35542053 DOI: 10.1007/s13205-022-03178-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2022] [Accepted: 03/31/2022] [Indexed: 11/01/2022] Open
Abstract
Toxin-antitoxin (TA) genetic modules have been found to widely exist in bacterial chromosomes and mobile genetic elements. They are composed of stable toxins and less stable antitoxins that can counteract the toxicity of toxins. The interactions between toxins and antitoxins could play critical roles in the virulence and persistence of pathogenic bacteria. There are at least eight types of TA systems which have been identified in a variety of bacteria. Vibrio, a genus of Gram-negative bacteria, is widespread in aquatic environments and can cause various human diseases, such as epidemic cholera. In this review, we mainly explore the structures and functions of TA modules found in common Vibrio pathogens, mainly V. cholerae, for better understanding of TA action mechanisms in pathogenic bacteria.
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13
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Tansirichaiya S, Winje E, Wigand J, Al-Haroni M. Inverse PCR-based detection reveal novel mobile genetic elements and their associated genes in the human oral metagenome. BMC Oral Health 2022; 22:210. [PMID: 35624467 PMCID: PMC9137128 DOI: 10.1186/s12903-022-02209-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2021] [Accepted: 05/03/2022] [Indexed: 11/20/2022] Open
Abstract
The human oral cavity is one of the hotspots harboring multiple mobile genetic elements (MGEs), which are segments of DNA that can move either within bacterial genomes or between bacterial cells that can facilitate the spreading of genetic materials, including antimicrobial resistance genes. It is, therefore, important to investigate genes associated with the MGEs as they have a high probability of dissemination within the bacterial population under selective pressure from human activities. As one-third of oral bacteria are not yet culturable in the laboratory condition, therefore, in this work, it is aimed to detect and identify the genetic contexts of MGEs in the oral cavity through an inverse PCR (IPCR)-based approach on the oral metagenomic. The human oral metagenome was extracted from saliva samples collected from healthy individuals in Tromsø, Norway. The extracted DNA was partially digested with the HindIII restriction enzyme and self-circularized by ligation. DNA primers targeting each MGE were designed to amplify outwards from the MGEs and used for the IPCR on the circularized DNA products. The IPCR amplicons were cloned into a pCR-XL-2-TOP vector, screened, and sequenced. Out of 40 IPCR amplicons, we confirmed and verified the genetic contexts of 11 samples amplified with primers targeting integron gene cassettes (GCs), IS431 composite transposons, and Tn916 conjugative transposons (tet(M) and xis-int). Novel integron GCs, MGEs, and variants of Tn916 conjugative transposons were identified, which is the first report using the IPCR technique to detect the genetic contexts of MGEs in the oral metagenomic DNA.
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Affiliation(s)
- Supathep Tansirichaiya
- Department of Microbiology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand
- Department of Clinical Dentistry, Faculty of Health Sciences, UiT the Arctic University of Norway, 9037, Tromsø, Norway
- Centre for New Antimicrobial Strategies, UiT the Arctic University of Norway, Tromsø, Norway
| | - Endre Winje
- Department of Clinical Dentistry, Faculty of Health Sciences, UiT the Arctic University of Norway, 9037, Tromsø, Norway
| | - Johannes Wigand
- Department of Clinical Dentistry, Faculty of Health Sciences, UiT the Arctic University of Norway, 9037, Tromsø, Norway
| | - Mohammed Al-Haroni
- Department of Clinical Dentistry, Faculty of Health Sciences, UiT the Arctic University of Norway, 9037, Tromsø, Norway.
- Centre for New Antimicrobial Strategies, UiT the Arctic University of Norway, Tromsø, Norway.
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14
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Ma L, Yang W, Huang S, Liu R, Li H, Huang X, Xiong J, Liu X. Integrative Assessments on Molecular Taxonomy of Acidiferrobacter thiooxydans ZJ and Its Environmental Adaptation Based on Mobile Genetic Elements. Front Microbiol 2022; 13:826829. [PMID: 35250944 PMCID: PMC8889020 DOI: 10.3389/fmicb.2022.826829] [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: 12/01/2021] [Accepted: 01/07/2022] [Indexed: 11/13/2022] Open
Abstract
Acidiferrobacter spp. are facultatively anaerobic acidophiles that belong to a distinctive Acidiferrobacteraceae family, which are similar to Ectothiorhodospiraceae phylogenetically, and are closely related to Acidithiobacillia class/subdivision physiologically. The limited genome information has kept them from being studied on molecular taxonomy and environmental adaptation in depth. Herein, Af. thiooxydans ZJ was isolated from acid mine drainage (AMD), and the complete genome sequence was reported to scan its genetic constitution for taxonomic and adaptative feature exploration. The genome has a single chromosome of 3,302,271 base pairs (bp), with a GC content of 63.61%. The phylogenetic tree based on OrthoANI highlighted the unique position of Af. thiooxydans ZJ, which harbored more unique genes among the strains from Ectothiorhodospiraceae and Acidithiobacillaceae by pan-genome analysis. The diverse mobile genetic elements (MGEs), such as insertion sequence (IS), clustered regularly interspaced short palindromic repeat (CRISPR), prophage, and genomic island (GI), have been identified and characterized in Af. thiooxydans ZJ. The results showed that Af. thiooxydans ZJ may effectively resist the infection of foreign viruses and gain functional gene fragments or clusters to shape its own genome advantageously. This study will offer more evidence of the genomic plasticity and improve our understanding of evolutionary adaptation mechanisms to extreme AMD environment, which could expand the potential utilization of Af. thiooxydans ZJ as an iron and sulfur oxidizer in industrial bioleaching.
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Affiliation(s)
- Liyuan Ma
- Hubei Key Laboratory of Yangtze Catchment Environmental Aquatic Science, School of Environmental Studies, China University of Geosciences, Wuhan, China.,Key Laboratory of Biometallurgy of Ministry of Education, Central South University, Changsha, China
| | - Weiyi Yang
- Hubei Key Laboratory of Yangtze Catchment Environmental Aquatic Science, School of Environmental Studies, China University of Geosciences, Wuhan, China
| | - Shanshan Huang
- Key Laboratory of Biometallurgy of Ministry of Education, Central South University, Changsha, China
| | - Rui Liu
- Hubei Key Laboratory of Yangtze Catchment Environmental Aquatic Science, School of Environmental Studies, China University of Geosciences, Wuhan, China
| | - Huiying Li
- Key Laboratory of Biometallurgy of Ministry of Education, Central South University, Changsha, China
| | - Xinping Huang
- Hubei Key Laboratory of Yangtze Catchment Environmental Aquatic Science, School of Environmental Studies, China University of Geosciences, Wuhan, China
| | - Junming Xiong
- Hubei Key Laboratory of Yangtze Catchment Environmental Aquatic Science, School of Environmental Studies, China University of Geosciences, Wuhan, China
| | - Xueduan Liu
- Key Laboratory of Biometallurgy of Ministry of Education, Central South University, Changsha, China
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15
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Choi E, Huh A, Oh C, Oh JI, Kang HY, Hwang J. Functional characterization of HigBA toxin-antitoxin system in an Arctic bacterium, Bosea sp. PAMC 26642. J Microbiol 2022; 60:192-206. [PMID: 35102526 DOI: 10.1007/s12275-022-1619-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2021] [Revised: 12/15/2021] [Accepted: 12/20/2021] [Indexed: 01/02/2023]
Abstract
Toxin-antitoxin (TA) systems are growth-controlling genetic elements consisting of an intracellular toxin protein and its cognate antitoxin. TA systems have been spread among microbial genomes through horizontal gene transfer and are now prevalent in most bacterial and archaeal genomes. Under normal growth conditions, antitoxins tightly counteract the activity of the toxins. Upon stresses, antitoxins are inactivated, releasing activated toxins, which induce growth arrest or cell death. In this study, among nine functional TA modules in Bosea sp. PAMC 26642 living in Arctic lichen, we investigated the functionality of BoHigBA2. BohigBA2 is located close to a genomic island and adjacent to flagellar gene clusters. The expression of BohigB2 induced the inhibition of E. coli growth at 37°C, which was more manifest at 18°C, and this growth defect was reversed when BohigA2 was co-expressed, suggesting that this BoHigBA2 module might be an active TA module in Bosea sp. PAMC 26642. Live/dead staining and viable count analyses revealed that the BoHigB2 toxin had a bactericidal effect, causing cell death. Furthermore, we demonstrated that BoHigB2 possessed mRNA-specific ribonuclease activity on various mRNAs and cleaved only mRNAs being translated, which might impede overall translation and consequently lead to cell death. Our study provides the insight to understand the cold adaptation of Bosea sp. PAMC 26642 living in the Arctic.
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Affiliation(s)
- Eunsil Choi
- Department of Microbiology, Pusan National University, Busan, 46241, Republic of Korea.,Microbiological Resource Research Institute, Pusan National University, Busan, 46241, Republic of Korea
| | - Ahhyun Huh
- Department of Microbiology, Pusan National University, Busan, 46241, Republic of Korea
| | - Changmin Oh
- Department of Microbiology, Pusan National University, Busan, 46241, Republic of Korea
| | - Jeong-Il Oh
- Department of Microbiology, Pusan National University, Busan, 46241, Republic of Korea.,Microbiological Resource Research Institute, Pusan National University, Busan, 46241, Republic of Korea
| | - Ho Young Kang
- Department of Microbiology, Pusan National University, Busan, 46241, Republic of Korea.,Microbiological Resource Research Institute, Pusan National University, Busan, 46241, Republic of Korea
| | - Jihwan Hwang
- Department of Microbiology, Pusan National University, Busan, 46241, Republic of Korea. .,Microbiological Resource Research Institute, Pusan National University, Busan, 46241, Republic of Korea.
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16
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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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17
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Abstract
Toxin-antitoxin systems are widespread in bacterial genomes. They are usually composed of two elements: a toxin that inhibits an essential cellular process and an antitoxin that counteracts its cognate toxin. In the past decade, a number of new toxin-antitoxin systems have been described, bringing new growth inhibition mechanisms to light as well as novel modes of antitoxicity. However, recent advances in the field profoundly questioned the role of these systems in bacterial physiology, stress response and antimicrobial persistence. This shifted the paradigm of the functions of toxin-antitoxin systems to roles related to interactions between hosts and their mobile genetic elements, such as viral defence or plasmid stability. In this Review, we summarize the recent progress in understanding the biology and evolution of these small genetic elements, and discuss how genomic conflicts could shape the diversification of toxin-antitoxin systems.
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18
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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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19
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Lau MSH, Sheng L, Zhang Y, Minton NP. Development of a Suite of Tools for Genome Editing in Parageobacillus thermoglucosidasius and Their Use to Identify the Potential of a Native Plasmid in the Generation of Stable Engineered Strains. ACS Synth Biol 2021; 10:1739-1749. [PMID: 34197093 DOI: 10.1021/acssynbio.1c00138] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The relentless rise in the levels of atmospheric greenhouse gases caused by the exploitation of fossil fuel necessitates the development of more environmentally friendly routes to the manufacture of chemicals and fuels. The exploitation of a fermentative process that uses a thermophilic chassis represents an attractive option. Its use, however, is hindered by a dearth of genetic tools. Here we expand on those available for the engineering of the industrial chassis Parageobacillus thermoglucosidasius through the assembly and testing of a range of promoters, ribosome binding sites, reporter genes, and the implementation of CRISPR/Cas9 genome editing based on two different thermostable Cas9 nucleases. The latter were used to demonstrate that the deletion of the two native plasmids carried by P. thermoglucosidasius, pNCI001 and pNCI002, either singly or in combination, had no discernible effects on the overall phenotypic characteristics of the organism. Through the CRISPR/Cas9-mediated insertion of the gene encoding a novel fluorescent reporter, eCGP123, we showed that pNCI001 exhibited a high degree of segregational stability. As the relatively higher copy number of pNCI001 led to higher levels of eCGP123 expression than when the same gene was integrated into the chromosome, we propose that pNCI001 represents the preferred option for the integration of metabolic operons when stable commercial strains are required.
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Affiliation(s)
- Matthew S. H. Lau
- BBSRC/EPSRC Synthetic Biology Research Centre (SBRC), Biodiscovery Institute, School of Life Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, U.K
| | - Lili Sheng
- BBSRC/EPSRC Synthetic Biology Research Centre (SBRC), Biodiscovery Institute, School of Life Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, U.K
| | - Ying Zhang
- BBSRC/EPSRC Synthetic Biology Research Centre (SBRC), Biodiscovery Institute, School of Life Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, U.K
| | - Nigel P. Minton
- BBSRC/EPSRC Synthetic Biology Research Centre (SBRC), Biodiscovery Institute, School of Life Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, U.K
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20
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Garcia-Rodriguez G, Girardin Y, Volkov AN, Singh RK, Muruganandam G, Van Dyck J, Sobott F, Versées W, Charlier D, Loris R. Entropic pressure controls the oligomerization of the Vibrio cholerae ParD2 antitoxin. Acta Crystallogr D Struct Biol 2021; 77:904-920. [PMID: 34196617 PMCID: PMC8251345 DOI: 10.1107/s2059798321004873] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2021] [Accepted: 05/07/2021] [Indexed: 11/22/2022] Open
Abstract
ParD2 is the antitoxin component of the parDE2 toxin-antitoxin module from Vibrio cholerae and consists of an ordered DNA-binding domain followed by an intrinsically disordered ParE-neutralizing domain. In the absence of the C-terminal intrinsically disordered protein (IDP) domain, V. cholerae ParD2 (VcParD2) crystallizes as a doughnut-shaped hexadecamer formed by the association of eight dimers. This assembly is stabilized via hydrogen bonds and salt bridges rather than by hydrophobic contacts. In solution, oligomerization of the full-length protein is restricted to a stable, open decamer or dodecamer, which is likely to be a consequence of entropic pressure from the IDP tails. The relative positioning of successive VcParD2 dimers mimics the arrangement of Streptococcus agalactiae CopG dimers on their operator and allows an extended operator to wrap around the VcParD2 oligomer.
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Affiliation(s)
- Gabriela Garcia-Rodriguez
- Structural Biology Brussels, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium
- VIB–VUB Center for Structural Biology, Vlaams Instituut voor Biotechnologie, Pleinlaan 2, 1050 Brussels, Belgium
| | - Yana Girardin
- Structural Biology Brussels, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium
- VIB–VUB Center for Structural Biology, Vlaams Instituut voor Biotechnologie, Pleinlaan 2, 1050 Brussels, Belgium
| | - Alexander N. Volkov
- Structural Biology Brussels, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium
- VIB–VUB Center for Structural Biology, Vlaams Instituut voor Biotechnologie, Pleinlaan 2, 1050 Brussels, Belgium
- Jean Jeener NMR Center, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium
| | - Ranjan Kumar Singh
- Structural Biology Brussels, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium
- VIB–VUB Center for Structural Biology, Vlaams Instituut voor Biotechnologie, Pleinlaan 2, 1050 Brussels, Belgium
| | - Gopinath Muruganandam
- Structural Biology Brussels, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium
- VIB–VUB Center for Structural Biology, Vlaams Instituut voor Biotechnologie, Pleinlaan 2, 1050 Brussels, Belgium
| | - Jeroen Van Dyck
- Department of Chemistry, Universiteit Antwerpen, Groenenborgerlaan 171, 2020 Antwerp, Belgium
| | - Frank Sobott
- Department of Chemistry, Universiteit Antwerpen, Groenenborgerlaan 171, 2020 Antwerp, Belgium
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - Wim Versées
- Structural Biology Brussels, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium
- VIB–VUB Center for Structural Biology, Vlaams Instituut voor Biotechnologie, Pleinlaan 2, 1050 Brussels, Belgium
| | - Daniel Charlier
- Research Group of Microbiology, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium
| | - Remy Loris
- Structural Biology Brussels, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium
- VIB–VUB Center for Structural Biology, Vlaams Instituut voor Biotechnologie, Pleinlaan 2, 1050 Brussels, Belgium
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21
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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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22
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Kamruzzaman M, Wu AY, Iredell JR. Biological Functions of Type II Toxin-Antitoxin Systems in Bacteria. Microorganisms 2021; 9:microorganisms9061276. [PMID: 34208120 PMCID: PMC8230891 DOI: 10.3390/microorganisms9061276] [Citation(s) in RCA: 51] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2021] [Revised: 06/04/2021] [Accepted: 06/07/2021] [Indexed: 12/14/2022] Open
Abstract
After the first discovery in the 1980s in F-plasmids as a plasmid maintenance system, a myriad of toxin-antitoxin (TA) systems has been identified in bacterial chromosomes and mobile genetic elements (MGEs), including plasmids and bacteriophages. TA systems are small genetic modules that encode a toxin and its antidote and can be divided into seven types based on the nature of the antitoxin molecules and their mechanism of action to neutralise toxins. Among them, type II TA systems are widely distributed in chromosomes and plasmids and the best studied so far. Maintaining genetic material may be the major function of type II TA systems associated with MGEs, but the chromosomal TA systems contribute largely to functions associated with bacterial physiology, including the management of different stresses, virulence and pathogenesis. Due to growing interest in TA research, extensive work has been conducted in recent decades to better understand the physiological roles of these chromosomally encoded modules. However, there are still controversies about some of the functions associated with different TA systems. This review will discuss the most current findings and the bona fide functions of bacterial type II TA systems.
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Affiliation(s)
- Muhammad Kamruzzaman
- Centre for Infectious Diseases and Microbiology, The Westmead Institute for Medical Research, The University of Sydney, Westmead, NSW 2145, Australia;
- Correspondence: (M.K.); (J.R.I.)
| | - Alma Y. Wu
- Centre for Infectious Diseases and Microbiology, The Westmead Institute for Medical Research, The University of Sydney, Westmead, NSW 2145, Australia;
| | - Jonathan R. Iredell
- Centre for Infectious Diseases and Microbiology, The Westmead Institute for Medical Research, The University of Sydney, Westmead, NSW 2145, Australia;
- Westmead Hospital, Westmead, NSW 2145, Australia
- Correspondence: (M.K.); (J.R.I.)
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23
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Abstract
Toxin-antitoxin modules function in the genetic stability of mobile genetic elements, bacteriophage defense, and antibiotic tolerance. A gain-of-function mutation of the Escherichia coli K-12 hipBA module can induce antibiotic tolerance in a subpopulation of bacterial cells, a phenomenon known as persistence. HipA is a Ser/Thr kinase that phosphorylates and inactivates glutamyl tRNA synthetase, inhibiting cellular translation and inducing the stringent response. Additional characterized HipA homologues include HipT from pathogenic E. coli O127 and YjjJ of E. coli K-12, which are encoded by tricistronic hipBST and monocistronic operons, respectively. The apparent diversity of HipA homologues in bacterial genomes inspired us to investigate overall phylogeny. Here, we present a comprehensive phylogenetic analysis of the Hip kinases in bacteria and archaea that expands on this diversity by revealing seven novel kinase families. Kinases of one family, encoded by monocistronic operons, consist of an N-terminal core kinase domain, a HipS-like domain, and a HIRAN (HIP116 Rad5p N-terminal) domain. HIRAN domains bind single- or double-stranded DNA ends. Moreover, five types of bicistronic kinase operons encode putative antitoxins with HipS-HIRAN, HipS, γδ-resolvase, or Stl repressor-like domains. Finally, our analysis indicates that reversion of hipBA gene order happened independently several times during evolution.
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24
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Xia K, Ma J, Liang X. Impacts of type II toxin-antitoxin systems on cell physiology and environmental behavior in acetic acid bacteria. Appl Microbiol Biotechnol 2021; 105:4357-4367. [PMID: 34021811 DOI: 10.1007/s00253-021-11357-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2021] [Revised: 05/08/2021] [Accepted: 05/16/2021] [Indexed: 12/19/2022]
Abstract
Acetic acid bacteria (AAB) are a group of Gram-negative and strictly aerobic microorganisms widely used in vinegar industry, especially the species belonging to the genera Acetobacter and Komagataeibacter. The environments inhabited by AAB during the vinegar fermentation, in particular those natural traditional bioprocesses, are complex and dynamically changed, usually accompanied by diverse microorganisms, bacteriophages, and the increasing acetic acid concentration. For this reason, how AAB survive to such harsh niches has always been an interesting research field. Previous omic analyses (e.g., genomics, proteomics, and transcriptomics) have provided abundant clues for the metabolic pathways and bioprocesses indispensable for the acid stress adaptation of AAB. Nevertheless, it is far from fully understanding what factors regulate these modular mechanisms overtly and covertly upon shifting environments. Bacterial toxin-antitoxin systems (TAS), usually consisting of a pair of genes encoding a stable toxin and an unstable antitoxin that is capable of counteracting the toxin, have been uncovered to have a variety of biological functions. Recent studies focusing on the role of TAS in Acetobacter pasteurianus suggest that TAS contribute substantially to the acid stress resistance. In this mini review, we discuss the biological functions of type II TAS in the context of AAB with regard to the acid stress resistance, persister formation and resuscitation, genome stability, and phage immunity. KEY POINTS: • Type II TAS act as regulators in the acid stress resistance of AAB. • Type II TAS are implicated in the formation of acid-tolerant persister cells in AAB. • Type II TAS are potential factors responsible for phage immunity and genome stability.
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Affiliation(s)
- Kai Xia
- School of Food Science and Biotechnology, Zhejiang Gongshang University, Hangzhou, 310018, China
| | - Jiawen Ma
- School of Food Science and Biotechnology, Zhejiang Gongshang University, Hangzhou, 310018, China.,Institute of Food Biotechnology, Zhejiang Gongshang University, Hangzhou, 310018, China
| | - Xinle Liang
- School of Food Science and Biotechnology, Zhejiang Gongshang University, Hangzhou, 310018, China. .,Institute of Food Biotechnology, Zhejiang Gongshang University, Hangzhou, 310018, China.
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25
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Luo X, Lin J, Yan J, Kuang X, Su H, Lin W, Luo L. Characterization of DinJ-YafQ toxin-antitoxin module in Tetragenococcus halophilus: activity, interplay, and evolution. Appl Microbiol Biotechnol 2021; 105:3659-3672. [PMID: 33877415 DOI: 10.1007/s00253-021-11297-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2021] [Revised: 04/05/2021] [Accepted: 04/12/2021] [Indexed: 11/26/2022]
Abstract
Tetragenococcus halophilus is a moderately halophilic lactic acid bacterium widely used in high-salt food fermentation because of its coping ability under various stress conditions. Bacterial toxin-antitoxin (TA) modules are widely distributed and play important roles in stress response, but those specific for genus Tetragenococcus have never been explored. Here, a bona fide TA module named DinJ1-YafQ1tha was characterized in T. halophilus. The toxin protein YafQ1tha acts as a ribonuclease, and its overexpression severely inhibits Escherichia coli growth. These toxic effects can be eliminated by introducing DinJ1tha, indicating that YafQ1tha activity is blocked by the formed DinJ1-YafQ1tha complex. In vivo and in vitro assays showed that DinJ1tha alone or DinJ1-YafQ1tha complex can repress the transcription of dinJ1-yafQ1tha operon by binding directly to the promoter sequence. In addition, dinJ1-yafQ1tha is involved in plasmid maintenance and stress response, and its transcriptional level is regulated by various stresses. These findings reveal the possible roles of DinJ1-YafQ1tha system in the stress adaptation processes of T. halophilus during fermentation. A single antitoxin DinJ2tha without a cognate toxin protein was also found. Its sequence shows low similarity to that of DinJ1tha, indicating that this antitoxin may have evolved from a different ancestor. Moreover, DinJ2tha can cross-interact with noncognate toxin YafQ1tha and cross-regulate with dinJ1-yafQ1tha operon. In summary, DinJ-YafQtha characterization may be helpful in investigating the key roles of TA systems in T. halophilus and serves as a foundation for further research. KEY POINTS: • dinJ1-yafQ1tha is the first functional TA module characterized in T. halophilus and upregulated significantly upon osmotic and acidic stress. • DinJ2tha can exhibit physical and transcriptional interplay with DinJ1-YafQ1tha. • dinJ2tha may be acquired from bacteria in distant affiliation and inserted into the T. halophilus genome through horizontal gene transfer.
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Affiliation(s)
- Xiaotong Luo
- School of Biology and Biological Engineering, South China University of Technology, Guangzhou, 510006, People's Republic of China
- Guangdong Provincial Key Laboratory of Fermentation and Enzyme Engineering, South China University of Technology, Guangzhou, 510006, People's Republic of China
| | - Jieting Lin
- School of Biology and Biological Engineering, South China University of Technology, Guangzhou, 510006, People's Republic of China
- Guangdong Provincial Key Laboratory of Fermentation and Enzyme Engineering, South China University of Technology, Guangzhou, 510006, People's Republic of China
| | - Junwei Yan
- School of Biology and Biological Engineering, South China University of Technology, Guangzhou, 510006, People's Republic of China
- Guangdong Provincial Key Laboratory of Fermentation and Enzyme Engineering, South China University of Technology, Guangzhou, 510006, People's Republic of China
| | - Xiaoxian Kuang
- School of Biology and Biological Engineering, South China University of Technology, Guangzhou, 510006, People's Republic of China
- Guangdong Provincial Key Laboratory of Fermentation and Enzyme Engineering, South China University of Technology, Guangzhou, 510006, People's Republic of China
| | - Hantao Su
- School of Biology and Biological Engineering, South China University of Technology, Guangzhou, 510006, People's Republic of China
- Guangdong Provincial Key Laboratory of Fermentation and Enzyme Engineering, South China University of Technology, Guangzhou, 510006, People's Republic of China
| | - Weifeng Lin
- School of Food Science and Engineering, South China University of Technology, Guangzhou, 510006, People's Republic of China
| | - Lixin Luo
- School of Biology and Biological Engineering, South China University of Technology, Guangzhou, 510006, People's Republic of China.
- Guangdong Provincial Key Laboratory of Fermentation and Enzyme Engineering, South China University of Technology, Guangzhou, 510006, People's Republic of China.
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26
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Antitoxin autoregulation of M. tuberculosis toxin-antitoxin expression through negative cooperativity arising from multiple inverted repeat sequences. Biochem J 2020; 477:2401-2419. [PMID: 32519742 PMCID: PMC7319586 DOI: 10.1042/bcj20200368] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2020] [Revised: 06/06/2020] [Accepted: 06/10/2020] [Indexed: 12/20/2022]
Abstract
Toxin-antitoxin systems play key roles in bacterial adaptation, including protection from antibiotic assault and infection by bacteriophages. The type IV toxin-antitoxin system AbiE encodes a DUF1814 nucleotidyltransferase-like toxin, and a two-domain antitoxin. In Streptococcus agalactiae, the antitoxin AbiEi negatively autoregulates abiE expression through positively co-operative binding to inverted repeats within the promoter. The human pathogen Mycobacterium tuberculosis encodes four DUF1814 putative toxins, two of which have antitoxins homologous to AbiEi. One such M. tuberculosis antitoxin, named Rv2827c, is required for growth and whilst the structure has previously been solved, the mode of regulation is unknown. To complete the gaps in our understanding, we first solved the structure of S. agalactiae AbiEi to 1.83 Å resolution for comparison with M. tuberculosis Rv2827c. AbiEi contains an N-terminal DNA binding domain and C-terminal antitoxicity domain, with bilateral faces of opposing charge. The overall AbiEi fold is similar to Rv2827c, though smaller, and with a 65° difference in C-terminal domain orientation. We further demonstrate that, like AbiEi, Rv2827c can autoregulate toxin-antitoxin operon expression. In contrast with AbiEi, the Prv2827c promoter contains two sets of inverted repeats, which bind Rv2827c with differing affinities depending on the sequence consensus. Surprisingly, Rv2827c bound with negative co-operativity to the full Prv2827c promoter, demonstrating an unexpectedly complex form of transcriptional regulation.
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27
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Klimkaitė L, Armalytė J, Skerniškytė J, Sužiedėlienė E. The Toxin-Antitoxin Systems of the Opportunistic Pathogen Stenotrophomonas maltophilia of Environmental and Clinical Origin. Toxins (Basel) 2020; 12:E635. [PMID: 33019620 PMCID: PMC7650669 DOI: 10.3390/toxins12100635] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2020] [Revised: 09/22/2020] [Accepted: 09/25/2020] [Indexed: 12/16/2022] Open
Abstract
Stenotrophomonas maltophilia is a ubiquitous environmental bacterium that has recently emerged as a multidrug-resistant opportunistic pathogen causing bloodstream, respiratory, and urinary tract infections. The connection between the commensal environmental S. maltophilia and the opportunistic pathogen strains is still under investigation. Bacterial toxin-antitoxin (TA) systems have been previously associated with pathogenic traits, such as biofilm formation and resistance to antibiotics, which are important in clinical settings. The same species of the bacterium can possess various sets of TAs, possibly influencing their overall stress response. While the TA systems of other important opportunistic pathogens have been researched, nothing is known about the TA systems of S. maltophilia. Here, we report the identification and characterization of S. maltophilia type II TA systems and their prevalence in the isolates of clinical and environmental origins. We found 49 putative TA systems by bioinformatic analysis in S. maltophilia genomes. Despite their even spread in sequenced S. maltophilia genomes, we observed that relBE, hicAB, and previously undescribed COG3832-ArsR operons were present solely in clinical S. maltophilia isolates collected in Lithuania, while hipBA was more frequent in the environmental ones. The kill-rescue experiments in Escherichia coli proved higBA, hicAB, and relBE systems to be functional TA modules. Together with different TA profiles, the clinical S. maltophilia isolates exhibited stronger biofilm formation, increased antibiotic, and serum resistance compared to environmental isolates. Such tendencies suggest that certain TA systems could be used as indicators of virulence traits.
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Affiliation(s)
| | - Julija Armalytė
- Institute of Biosciences, Life Sciences Center, Vilnius University, LT-1025 Vilnius, Lithuania; (L.K.); (J.S.)
| | | | - Edita Sužiedėlienė
- Institute of Biosciences, Life Sciences Center, Vilnius University, LT-1025 Vilnius, Lithuania; (L.K.); (J.S.)
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28
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Zaveri A, Wang R, Botella L, Sharma R, Zhu L, Wallach JB, Song N, Jansen RS, Rhee KY, Ehrt S, Schnappinger D. Depletion of the DarG antitoxin in Mycobacterium tuberculosis triggers the DNA-damage response and leads to cell death. Mol Microbiol 2020; 114:641-652. [PMID: 32634279 PMCID: PMC7689832 DOI: 10.1111/mmi.14571] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2020] [Revised: 06/28/2020] [Accepted: 07/01/2020] [Indexed: 01/01/2023]
Abstract
Of the ~80 putative toxin-antitoxin (TA) modules encoded by the bacterial pathogen Mycobacterium tuberculosis (Mtb), three contain antitoxins essential for bacterial viability. One of these, Rv0060 (DNA ADP-ribosyl glycohydrolase, DarGMtb ), functions along with its cognate toxin Rv0059 (DNA ADP-ribosyl transferase, DarTMtb ), to mediate reversible DNA ADP-ribosylation (Jankevicius et al., 2016). We demonstrate that DarTMtb -DarGMtb form a functional TA pair and essentiality of darGMtb is dependent on the presence of darTMtb , but simultaneous deletion of both darTMtb -darGMtb does not alter viability of Mtb in vitro or in mice. The antitoxin, DarGMtb , forms a cytosolic complex with DNA-repair proteins that assembles independently of either DarTMtb or interaction with DNA. Depletion of DarGMtb alone is bactericidal, a phenotype that is rescued by expression of an orthologous antitoxin, DarGTaq , from Thermus aquaticus. Partial depletion of DarGMtb triggers a DNA-damage response and sensitizes Mtb to drugs targeting DNA metabolism and respiration. Induction of the DNA-damage response is essential for Mtb to survive partial DarGMtb -depletion and leads to a hypermutable phenotype.
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Affiliation(s)
- Anisha Zaveri
- Department of Microbiology and Immunology, Weill Cornell Medicine, New York, NY, USA
| | - Ruojun Wang
- Department of Microbiology and Immunology, Weill Cornell Medicine, New York, NY, USA
| | - Laure Botella
- Department of Microbiology and Immunology, Weill Cornell Medicine, New York, NY, USA
| | - Ritu Sharma
- Department of Microbiology and Immunology, Weill Cornell Medicine, New York, NY, USA
| | - Linnan Zhu
- Department of Microbiology and Immunology, Weill Cornell Medicine, New York, NY, USA
| | - Joshua B Wallach
- Department of Microbiology and Immunology, Weill Cornell Medicine, New York, NY, USA
| | - Naomi Song
- Department of Microbiology and Immunology, Weill Cornell Medicine, New York, NY, USA
| | - Robert S Jansen
- Department of Medicine, Weill Cornell Medicine, New York, NY, USA
| | - Kyu Y Rhee
- Department of Medicine, Weill Cornell Medicine, New York, NY, USA
| | - Sabine Ehrt
- Department of Microbiology and Immunology, Weill Cornell Medicine, New York, NY, USA
| | - Dirk Schnappinger
- Department of Microbiology and Immunology, Weill Cornell Medicine, New York, NY, USA
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29
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Buongermino Pereira M, Österlund T, Eriksson KM, Backhaus T, Axelson-Fisk M, Kristiansson E. A comprehensive survey of integron-associated genes present in metagenomes. BMC Genomics 2020; 21:495. [PMID: 32689930 PMCID: PMC7370490 DOI: 10.1186/s12864-020-06830-5] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2019] [Accepted: 06/15/2020] [Indexed: 12/19/2022] Open
Abstract
Background Integrons are genomic elements that mediate horizontal gene transfer by inserting and removing genetic material using site-specific recombination. Integrons are commonly found in bacterial genomes, where they maintain a large and diverse set of genes that plays an important role in adaptation and evolution. Previous studies have started to characterize the wide range of biological functions present in integrons. However, the efforts have so far mainly been limited to genomes from cultivable bacteria and amplicons generated by PCR, thus targeting only a small part of the total integron diversity. Metagenomic data, generated by direct sequencing of environmental and clinical samples, provides a more holistic and unbiased analysis of integron-associated genes. However, the fragmented nature of metagenomic data has previously made such analysis highly challenging. Results Here, we present a systematic survey of integron-associated genes in metagenomic data. The analysis was based on a newly developed computational method where integron-associated genes were identified by detecting their associated recombination sites. By processing contiguous sequences assembled from more than 10 terabases of metagenomic data, we were able to identify 13,397 unique integron-associated genes. Metagenomes from marine microbial communities had the highest occurrence of integron-associated genes with levels more than 100-fold higher than in the human microbiome. The identified genes had a large functional diversity spanning over several functional classes. Genes associated with defense mechanisms and mobility facilitators were most overrepresented and more than five times as common in integrons compared to other bacterial genes. As many as two thirds of the genes were found to encode proteins of unknown function. Less than 1% of the genes were associated with antibiotic resistance, of which several were novel, previously undescribed, resistance gene variants. Conclusions Our results highlight the large functional diversity maintained by integrons present in unculturable bacteria and significantly expands the number of described integron-associated genes.
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Affiliation(s)
- Mariana Buongermino Pereira
- Department of Mathematical Sciences, Chalmers University of Technology, Gothenburg, Sweden.,Centre for Antibiotic Resistance Research (CARe) at University of Gothenburg, Gothenburg, Sweden
| | - Tobias Österlund
- Department of Mathematical Sciences, Chalmers University of Technology, Gothenburg, Sweden.,Centre for Antibiotic Resistance Research (CARe) at University of Gothenburg, Gothenburg, Sweden
| | - K Martin Eriksson
- Department of Biological and Environmental Sciences, University of Gothenburg, Gothenburg, Sweden.,Gothenburg Centre for Sustainable Development, Chalmers University of Technology, Gothenburg, Sweden
| | - Thomas Backhaus
- Centre for Antibiotic Resistance Research (CARe) at University of Gothenburg, Gothenburg, Sweden.,Department of Biological and Environmental Sciences, University of Gothenburg, Gothenburg, Sweden
| | - Marina Axelson-Fisk
- Department of Mathematical Sciences, Chalmers University of Technology, Gothenburg, Sweden
| | - Erik Kristiansson
- Department of Mathematical Sciences, Chalmers University of Technology, Gothenburg, Sweden. .,Centre for Antibiotic Resistance Research (CARe) at University of Gothenburg, Gothenburg, Sweden.
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30
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Cai Y, Usher B, Gutierrez C, Tolcan A, Mansour M, Fineran PC, Condon C, Neyrolles O, Genevaux P, Blower TR. A nucleotidyltransferase toxin inhibits growth of Mycobacterium tuberculosis through inactivation of tRNA acceptor stems. SCIENCE ADVANCES 2020; 6:eabb6651. [PMID: 32923609 PMCID: PMC7450476 DOI: 10.1126/sciadv.abb6651] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2020] [Accepted: 06/12/2020] [Indexed: 05/12/2023]
Abstract
Toxin-antitoxin systems are widespread stress-responsive elements, many of whose functions remain largely unknown. Here, we characterize the four DUF1814-family nucleotidyltransferase-like toxins (MenT1-4) encoded by the human pathogen Mycobacterium tuberculosis. Toxin MenT3 inhibited growth of M. tuberculosis when not antagonized by its cognate antitoxin, MenA3. We solved the structures of toxins MenT3 and MenT4 to 1.6 and 1.2 Å resolution, respectively, and identified the biochemical activity and target of MenT3. MenT3 blocked in vitro protein expression and prevented tRNA charging in vivo. MenT3 added pyrimidines (C or U) to the 3'-CCA acceptor stems of uncharged tRNAs and exhibited strong substrate specificity in vitro, preferentially targeting tRNASer from among the 45 M. tuberculosis tRNAs. Our study identifies a previously unknown mechanism that expands the range of enzymatic activities used by bacterial toxins, uncovering a new way to block protein synthesis and potentially treat tuberculosis and other infections.
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Affiliation(s)
- Yiming Cai
- Laboratoire de Microbiologie et Génétique Moléculaires, Centre de Biologie Intégrative, Université de Toulouse, CNRS, UPS, 118 route de Narbonne, 31400 Toulouse, France
| | - Ben Usher
- Department of Biosciences, Durham University, South Road, Durham DH1 3LE, UK
| | - Claude Gutierrez
- Institut de Pharmacologie et de Biologie Structurale, IPBS, Université de Toulouse, CNRS, UPS, 205 route de Narbonne, 31400 Toulouse, France
| | - Anastasia Tolcan
- UMR8261 (CNRS, Université de Paris), Institut de Biologie Physico-Chimique, 13 rue Pierre et Marie Curie, 75005 Paris, France
| | - Moise Mansour
- Laboratoire de Microbiologie et Génétique Moléculaires, Centre de Biologie Intégrative, Université de Toulouse, CNRS, UPS, 118 route de Narbonne, 31400 Toulouse, France
| | - Peter C. Fineran
- Department of Microbiology and Immunology, University of Otago, PO Box 56, Dunedin 9054, New Zealand
- Genetics Otago, University of Otago, PO Box 56, Dunedin 9054, New Zealand
- Bio-protection Research Centre, University of Otago, PO Box 56, Dunedin 9054, New Zealand
| | - Ciarán Condon
- UMR8261 (CNRS, Université de Paris), Institut de Biologie Physico-Chimique, 13 rue Pierre et Marie Curie, 75005 Paris, France
| | - Olivier Neyrolles
- Institut de Pharmacologie et de Biologie Structurale, IPBS, Université de Toulouse, CNRS, UPS, 205 route de Narbonne, 31400 Toulouse, France
| | - Pierre Genevaux
- Laboratoire de Microbiologie et Génétique Moléculaires, Centre de Biologie Intégrative, Université de Toulouse, CNRS, UPS, 118 route de Narbonne, 31400 Toulouse, France
| | - Tim R. Blower
- Department of Biosciences, Durham University, South Road, Durham DH1 3LE, UK
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31
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Jurėnas D, Van Melderen L. The Variety in the Common Theme of Translation Inhibition by Type II Toxin-Antitoxin Systems. Front Genet 2020; 11:262. [PMID: 32362907 PMCID: PMC7180214 DOI: 10.3389/fgene.2020.00262] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2019] [Accepted: 03/05/2020] [Indexed: 12/12/2022] Open
Abstract
Type II Toxin–antitoxin (TA) modules are bacterial operons that encode a toxic protein and its antidote, which form a self-regulating genetic system. Antitoxins put a halter on toxins in many ways that distinguish different types of TA modules. In type II TA modules, toxin and antitoxin are proteins that form a complex which physically sequesters the toxin, thereby preventing its toxic activity. Type II toxins inhibit various cellular processes, however, the translation process appears to be their favorite target and nearly every step of this complex process is inhibited by type II toxins. The structural features, enzymatic activities and target specificities of the different toxin families are discussed. Finally, this review emphasizes that the structural folds presented by these toxins are not restricted to type II TA toxins or to one particular cellular target, and discusses why so many of them evolved to target translation as well as the recent developments regarding the role(s) of these systems in bacterial physiology and evolution.
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Affiliation(s)
- Dukas Jurėnas
- Laboratoire d'Ingénierie des Systèmes Macromoléculaires, Institut de Microbiologie de la Méditerranée, CNRS, Aix-Marseille Université, Marseille, France
| | - Laurence Van Melderen
- Cellular and Molecular Microbiology, Faculté des Sciences, Université libre de Bruxelles, Gosselies, Belgium
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32
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Aghera NK, Prabha J, Tandon H, Chattopadhyay G, Vishwanath S, Srinivasan N, Varadarajan R. Mechanism of CcdA-Mediated Rejuvenation of DNA Gyrase. Structure 2020; 28:562-572.e4. [PMID: 32294467 DOI: 10.1016/j.str.2020.03.006] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2019] [Revised: 02/17/2020] [Accepted: 03/17/2020] [Indexed: 12/13/2022]
Abstract
Most biological processes involve formation of transient complexes where binding of a ligand allosterically modulates function. The ccd toxin-antitoxin system is involved in plasmid maintenance and bacterial persistence. The CcdA antitoxin accelerates dissociation of CcdB from its complex with DNA gyrase, binds and neutralizes CcdB, but the mechanistic details are unclear. Using a series of experimental and computational approaches, we demonstrate the formation of transient ternary and quaternary CcdA:CcdB:gyrase complexes and delineate the molecular steps involved in the rejuvenation process. Binding of region 61-72 of CcdA to CcdB induces the vital structural and dynamic changes required to facilitate dissociation from gyrase, region 50-60 enhances the dissociation process through additional allosteric effects, and segment 37-49 prevents gyrase rebinding. This study provides insights into molecular mechanisms responsible for recovery of CcdB-poisoned cells from a persister-like state. Similar methodology can be used to characterize other important transient, macromolecular complexes.
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Affiliation(s)
- Nilesh K Aghera
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560 012, India
| | - Jyothi Prabha
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560 012, India
| | - Himani Tandon
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560 012, India
| | | | - Sneha Vishwanath
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560 012, India
| | | | - Raghavan Varadarajan
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560 012, India; Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur P.O., Bangalore 560 004, India.
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Abstract
Type II toxin-antitoxin (TA) systems are small genetic elements composed of a toxic protein and its cognate antitoxin protein, the latter counteracting the toxicity of the former. While TA systems were initially discovered on plasmids, functioning as addiction modules through a phenomenon called postsegregational killing, they were later shown to be massively present in bacterial chromosomes, often in association with mobile genetic elements. Extensive research has been conducted in recent decades to better understand the physiological roles of these chromosomally encoded modules and to characterize the conditions leading to their activation. Type II toxin-antitoxin (TA) systems are small genetic elements composed of a toxic protein and its cognate antitoxin protein, the latter counteracting the toxicity of the former. While TA systems were initially discovered on plasmids, functioning as addiction modules through a phenomenon called postsegregational killing, they were later shown to be massively present in bacterial chromosomes, often in association with mobile genetic elements. Extensive research has been conducted in recent decades to better understand the physiological roles of these chromosomally encoded modules and to characterize the conditions leading to their activation. The diversity of their proposed roles, ranging from genomic stabilization and abortive phage infection to stress modulation and antibiotic persistence, in conjunction with the poor understanding of TA system regulation, resulted in the generation of simplistic models, often refuted by contradictory results. This review provides an epistemological and critical retrospective on TA modules and highlights fundamental questions concerning their roles and regulations that still remain unanswered.
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Reassessing the Role of the Type II MqsRA Toxin-Antitoxin System in Stress Response and Biofilm Formation: mqsA Is Transcriptionally Uncoupled from mqsR. mBio 2019; 10:mBio.02678-19. [PMID: 31848281 PMCID: PMC6918082 DOI: 10.1128/mbio.02678-19] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Toxin-antitoxin (TA) systems are broadly distributed modules whose biological roles remain mostly unknown. The mqsRA system is a noncanonical TA system in which the toxin and antitoxins genes are organized in operon but with the particularity that the toxin gene precedes that of the antitoxin. This system was shown to regulate global processes such as resistance to bile salts, motility, and biofilm formation. In addition, the MqsA antitoxin was shown to be a master regulator that represses the transcription of the csgD, cspD, and rpoS global regulator genes, thereby displaying a pleiotropic regulatory role. Here, we identified two promoters located in the toxin sequence driving the constitutive expression of mqsA, allowing thereby excess production of the MqsA antitoxin compared to the MqsR toxin. Our results show that both antitoxin-specific and operon promoters are not regulated by stresses such as amino acid starvation, oxidative shock, or bile salts. Moreover, we show that the MqsA antitoxin is not a global regulator as suggested, since the expression of csgD, cspD and rpoS is similar in wild-type and ΔmqsRA mutant strains. Moreover, these two strains behave similarly in terms of biofilm formation and sensitivity to oxidative stress or bile salts.IMPORTANCE There is growing controversy regarding the role of chromosomal toxin-antitoxin systems in bacterial physiology. mqsRA is a peculiar toxin-antitoxin system, as the gene encoding the toxin precedes that of the antitoxin. This system was previously shown to play a role in stress response and biofilm formation. In this work, we identified two promoters specifically driving the constitutive expression of the antitoxin, thereby decoupling the expression of antitoxin from the toxin. We also showed that mqsRA contributes neither to the regulation of biofilm formation nor to the sensitivity to oxidative stress and bile salts. Finally, we were unable to confirm that the MqsA antitoxin is a global regulator. Altogether, our data are ruling out the involvement of the mqsRA system in Escherichia coli regulatory networks.
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Abstract
Abstract
Purpose
The aquaculture sector is a major contributor to the economic and nutritional security for a number of countries. India’s total seafood exports for the year 2017–2018 accounted for US$ Million 7082. One of the major setbacks in this sector is the frequent outbreaks of diseases often due to bacterial pathogens. Vibriosis is one of the major diseases caused by bacteria of Vibrio spp., causing significant economic loss to the aquaculture sector. The objective of this study was to understand the genetic composition of Vibrio spp.
Methods
Thirty-five complete genomes were downloaded from GenBank comprising seven vibrio species, namely, Vibrio alginolyticus, V. anguillarum, V. campbellii, V. harveyi, V. furnissii, V. parahaemolyticus, and V. vulnificus. Pan-genome analysis was carried out with coding sequences (CDS) generated from all the Vibrio genomes. In addition, genomes were mined for genes coding for toxin-antitoxin systems, antibiotic resistance, genomic islands, and virulence factors.
Results
Results revealed an open pan-genome comprising of 2004 core, 8249 accessory, and 6780 unique genes. Downstream analysis of genomes and the identified unique genes resulted in 312 antibiotic resistance genes, 430 genes coding for toxin and antitoxin systems along with 4802, and 4825 putative virulent genes from genomic island regions and unique gene sets, respectively.
Conclusion
Pan-genome and other downstream analytical procedures followed in this study have the potential to predict strain-specific genes and their association with habitat and pathogenicity.
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Zamakhaev MV, Goncharenko AV, Shumkov MS. Toxin-Antitoxin Systems and Bacterial Persistence (Review). APPL BIOCHEM MICRO+ 2019. [DOI: 10.1134/s0003683819060140] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Towards Exploring Toxin-Antitoxin Systems in Geobacillus: A Screen for Type II Toxin-Antitoxin System Families in a Thermophilic Genus. Int J Mol Sci 2019; 20:ijms20235869. [PMID: 31771094 PMCID: PMC6929052 DOI: 10.3390/ijms20235869] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2019] [Revised: 11/12/2019] [Accepted: 11/20/2019] [Indexed: 12/19/2022] Open
Abstract
The toxin-antitoxin (TA) systems have been attracting attention due to their role in regulating stress responses in prokaryotes and their biotechnological potential. Much recognition has been given to type II TA system of mesophiles, while thermophiles have received merely limited attention. Here, we are presenting the putative type II TA families encoded on the genomes of four Geobacillus strains. We employed the TA finder tool to mine for TA-coding genes and manually curated the results using protein domain analysis tools. We also used the NCBI BLAST, Operon Mapper, ProOpDB, and sequence alignment tools to reveal the geobacilli TA features. We identified 28 putative TA pairs, distributed over eight TA families. Among the identified TAs, 15 represent putative novel toxins and antitoxins, belonging to the MazEF, MNT-HEPN, ParDE, RelBE, and XRE-COG2856 TA families. We also identified a potentially new TA composite, AbrB-ParE. Furthermore, we are suggesting the Geobacillus acetyltransferase TA (GacTA) family, which potentially represents one of the unique TA families with a reverse gene order. Moreover, we are proposing a hypothesis on the xre-cog2856 gene expression regulation, which seems to involve the c-di-AMP. This study aims for highlighting the significance of studying TAs in Geobacillus and facilitating future experimental research.
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A ParDE-family toxin antitoxin system in major resistance plasmids of Enterobacteriaceae confers antibiotic and heat tolerance. Sci Rep 2019; 9:9872. [PMID: 31285520 PMCID: PMC6614396 DOI: 10.1038/s41598-019-46318-1] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2019] [Accepted: 06/26/2019] [Indexed: 11/16/2022] Open
Abstract
Toxin-antitoxin (TA) systems were initially discovered as plasmid addiction systems on low-copy-number plasmids. Thousands of TA loci have since been identified on chromosomes, plasmids and mobile elements in bacteria and archaea with diverse roles in bacterial physiology and in maintenance of genetic elements. Here, we identified and characterised a plasmid mediated type II TA system in Enterobacteriaceae as a member of the ParDE super family. This system (hereafter, ParDEI) is distributed among IncI and IncF-type antibiotic resistance and virulence plasmids found in avian and human-source Escherichia coli and Salmonella. It is found that ParDEI is a plasmid stability and stress response module that increases tolerance of aminoglycoside, quinolone and β-lactam antibiotics in E. coli by ~100–1,000-fold, and thus to levels beyond those achievable in the course of antibiotic therapy for human infections. ParDEI also confers a clear survival advantage at 42 °C and expression of the ParEI toxin in trans induces the SOS response, inhibits cell division and promotes biofilm formation. This transmissible high-level antibiotic tolerance is likely to be an important factor in the success of the IncI and IncF plasmids which carry it and the important pathogens in which these are resident.
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Tansirichaiya S, Mullany P, Roberts AP. Promoter activity of ORF-less gene cassettes isolated from the oral metagenome. Sci Rep 2019; 9:8388. [PMID: 31182805 PMCID: PMC6557892 DOI: 10.1038/s41598-019-44640-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2018] [Accepted: 05/17/2019] [Indexed: 01/09/2023] Open
Abstract
Integrons are genetic elements consisting of a functional platform for recombination and expression of gene cassettes (GCs). GCs usually carry promoter-less open reading frames (ORFs), encoding proteins with various functions including antibiotic resistance. The transcription of GCs relies mainly on a cassette promoter (PC), located upstream of an array of GCs. Some integron GCs, called ORF-less GCs, contain no identifiable ORF with a small number shown to be involved in antisense mRNA mediated gene regulation. In this study, the promoter activity of ORF-less GCs, previously recovered from the oral metagenome, was verified by cloning them upstream of a gusA reporter, proving they can function as a promoter, presumably allowing bacteria to adapt to multiple stresses within the complex physico-chemical environment of the human oral cavity. A bi-directional promoter detection system was also developed allowing direct identification of clones with promoter-containing GCs on agar plates. Novel promoter-containing GCs were identified from the human oral metagenomic DNA using this construct, called pBiDiPD. This is the first demonstration and detection of promoter activity of ORF-less GCs from Treponema bacteria and the development of an agar plate-based detection system will enable similar studies in other environments.
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Affiliation(s)
- Supathep Tansirichaiya
- Department of Microbial Diseases, University College London, Eastman Dental Institute, 256 Gray's Inn Road, London, WC1X 8LD, UK.,Department of Clinical Dentistry, Faculty of Health Sciences, UiT the Arctic University of Norway, Tromsø, Norway
| | - Peter Mullany
- Department of Microbial Diseases, University College London, Eastman Dental Institute, 256 Gray's Inn Road, London, WC1X 8LD, UK
| | - Adam P Roberts
- Department of Microbial Diseases, University College London, Eastman Dental Institute, 256 Gray's Inn Road, London, WC1X 8LD, UK. .,Department of Tropical Disease Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK.
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Soutourina O. Type I Toxin-Antitoxin Systems in Clostridia. Toxins (Basel) 2019; 11:toxins11050253. [PMID: 31064056 PMCID: PMC6563280 DOI: 10.3390/toxins11050253] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2019] [Revised: 04/30/2019] [Accepted: 05/02/2019] [Indexed: 12/20/2022] Open
Abstract
Type I toxin-antitoxin (TA) modules are abundant in both bacterial plasmids and chromosomes and usually encode a small hydrophobic toxic protein and an antisense RNA acting as an antitoxin. The RNA antitoxin neutralizes toxin mRNA by inhibiting its translation and/or promoting its degradation. This review summarizes our current knowledge of the type I TA modules identified in Clostridia species focusing on the recent findings in the human pathogen Clostridium difficile. More than ten functional type I TA modules have been identified in the genome of this emerging enteropathogen that could potentially contribute to its fitness and success inside the host. Despite the absence of sequence homology, the comparison of these newly identified type I TA modules with previously studied systems in other Gram-positive bacteria, i.e., Bacillus subtilis and Staphylococcus aureus, revealed some important common traits. These include the conservation of characteristic sequence features for small hydrophobic toxic proteins, the localization of several type I TA within prophage or prophage-like regions and strong connections with stress response. Potential functions in the stabilization of genome regions, adaptations to stress conditions and interactions with CRISPR-Cas defence system, as well as promising applications of TA for genome-editing and antimicrobial developments are discussed.
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Affiliation(s)
- Olga Soutourina
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Université Paris-Saclay, 91198 Gif-sur-Yvette CEDEX, France.
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Spread and Persistence of Virulence and Antibiotic Resistance Genes: A Ride on the F Plasmid Conjugation Module. EcoSal Plus 2019; 8. [PMID: 30022749 DOI: 10.1128/ecosalplus.esp-0003-2018] [Citation(s) in RCA: 55] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The F plasmid or F-factor is a large, 100-kbp, circular conjugative plasmid of Escherichia coli and was originally described as a vector for horizontal gene transfer and gene recombination in the late 1940s. Since then, F and related F-like plasmids have served as role models for bacterial conjugation. At present, more than 200 different F-like plasmids with highly related DNA transfer genes, including those for the assembly of a type IV secretion apparatus, are completely sequenced. They belong to the phylogenetically related MOBF12A group. F-like plasmids are present in enterobacterial hosts isolated from clinical as well as environmental samples all over the world. As conjugative plasmids, F-like plasmids carry genetic modules enabling plasmid replication, stable maintenance, and DNA transfer. In this plasmid backbone of approximately 60 kbp, the DNA transfer genes occupy the largest and mostly conserved part. Subgroups of MOBF12A plasmids can be defined based on the similarity of TraJ, a protein required for DNA transfer gene expression. In addition, F-like plasmids harbor accessory cargo genes, frequently embedded within transposons and/or integrons, which harness their host bacteria with antibiotic resistance and virulence genes, causing increasingly severe problems for the treatment of infectious diseases. Here, I focus on key genetic elements and their encoded proteins present on the F-factor and other typical F-like plasmids belonging to the MOBF12A group of conjugative plasmids.
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Bardaji L, Añorga M, Echeverría M, Ramos C, Murillo J. The toxic guardians - multiple toxin-antitoxin systems provide stability, avoid deletions and maintain virulence genes of Pseudomonas syringae virulence plasmids. Mob DNA 2019; 10:7. [PMID: 30728866 PMCID: PMC6354349 DOI: 10.1186/s13100-019-0149-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2018] [Accepted: 01/18/2019] [Indexed: 02/05/2023] Open
Abstract
Background Pseudomonas syringae is a γ-proteobacterium causing economically relevant diseases in practically all cultivated plants. Most isolates of this pathogen contain native plasmids collectively carrying many pathogenicity and virulence genes. However, P. syringae is generally an opportunistic pathogen primarily inhabiting environmental reservoirs, which could exert a low selective pressure for virulence plasmids. Additionally, these plasmids usually contain a large proportion of repeated sequences, which could compromise plasmid integrity. Therefore, the identification of plasmid stability determinants and mechanisms to preserve virulence genes is essential to understand the evolution of this pathogen and its adaptability to agroecosystems. Results The three virulence plasmids of P. syringae pv. savastanoi NCPPB 3335 contain from one to seven functional stability determinants, including three highly active toxin-antitoxin systems (TA) in both pPsv48A and pPsv48C. The TA systems reduced loss frequency of pPsv48A by two orders of magnitude, whereas one of the two replicons of pPsv48C likely confers stable inheritance by itself. Notably, inactivation of the TA systems from pPsv48C exposed the plasmid to high-frequency deletions promoted by mobile genetic elements. Thus, recombination between two copies of MITEPsy2 caused the deletion of an 8.3 kb fragment, with a frequency of 3.8 ± 0.3 × 10− 3. Likewise, one-ended transposition of IS801 generated plasmids containing deletions of variable size, with a frequency of 5.5 ± 2.1 × 10− 4, of which 80% had lost virulence gene idi. These deletion derivatives were stably maintained in the population by replication mediated by repJ, which is adjacent to IS801. IS801 also promoted deletions in plasmid pPsv48A, either by recombination or one-ended transposition. In all cases, functional TA systems contributed significantly to reduce the occurrence of plasmid deletions in vivo. Conclusions Virulence plasmids from P. syringae harbour a diverse array of stability determinants with a variable contribution to plasmid persistence. Importantly, we showed that multiple plasmid-borne TA systems have a prominent role in preserving plasmid integrity and ensuring the maintenance of virulence genes in free-living conditions. This strategy is likely widespread amongst native plasmids of P. syringae and other bacteria. Electronic supplementary material The online version of this article (10.1186/s13100-019-0149-4) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Leire Bardaji
- 1Institute for Multidisciplinary Applied Biology, Universidad Pública de Navarra, 31192 Mutilva, Spain
| | - Maite Añorga
- 1Institute for Multidisciplinary Applied Biology, Universidad Pública de Navarra, 31192 Mutilva, Spain
| | - Myriam Echeverría
- 1Institute for Multidisciplinary Applied Biology, Universidad Pública de Navarra, 31192 Mutilva, Spain
| | - Cayo Ramos
- 2Instituto de Hortofruticultura Subtropical y Mediterránea «La Mayora», Universidad de Málaga-CSIC, Área de Genética, Universidad de Málaga, Campus de Teatinos s/n, 29010 Málaga, Spain
| | - Jesús Murillo
- 1Institute for Multidisciplinary Applied Biology, Universidad Pública de Navarra, 31192 Mutilva, Spain
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A toxin-antitoxin system is essential for the stability of mosquitocidal plasmid pBsph of Lysinibacillus sphaericus. Microbiol Res 2018; 214:114-122. [PMID: 30031473 DOI: 10.1016/j.micres.2018.06.013] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2018] [Revised: 06/13/2018] [Accepted: 06/23/2018] [Indexed: 11/22/2022]
Abstract
Lysinibacillus sphaericus C3-41 carries a large low-copy-number plasmid pBsph, which encodes binary toxin proteins. Our previous study found that the transcriptional activator TubX plays an important role in the newly identified type Ⅲ TubRZC replication/partition system in pBsph, and that a vector consisting of tubRZC and tubX is not as stable as pBsph, indicating the presence of other maintenance module(s). In this study, we identified that orf9 and orf10 are necessary for the stability of pBsph by a series of deletion and complementation experiments. Bioinformatics analysis showed that ORF9 contains a PIN domain of VapBC toxin-antitoxin (TA) system, whereas ORF10 share no significant sequence similarity to any of the characterized antitoxins in the database. Further studies revealed that orf9 and orf10 are transcribed as an operon. The overexpression of ORF9 repressed the growth of both Escherichia coli and L. sphaericus, which can be alleviated by overexpression of ORF10. The deletion of orf10 individually or orf9-10 together resulted a decrease on plasmid stability which was restored by the complementation of corresponding gene(s), suggesting that ORF10 plays an important role in plasmid stability. In addition, it was found the plasmid stability is related with the transcription level of tubRZ, and overexpression of TubRZ could neutralize the negative effect on plasmid stability caused by the deletion of orf9-orf10. Moreover, the recombinant vector containing tubRZC, tubX and orf9-10 was more stable than the ones containing only tubRZC and either tubX or orf9-10. The data indicate that the plasmid maintenance system on pBsph includes orf9-orf10 TA system.
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Reassessing the Role of Type II Toxin-Antitoxin Systems in Formation of Escherichia coli Type II Persister Cells. mBio 2018; 9:mBio.00640-18. [PMID: 29895634 PMCID: PMC6016239 DOI: 10.1128/mbio.00640-18] [Citation(s) in RCA: 120] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Persistence is a reversible and low-frequency phenomenon allowing a subpopulation of a clonal bacterial population to survive antibiotic treatments. Upon removal of the antibiotic, persister cells resume growth and give rise to viable progeny. Type II toxin-antitoxin (TA) systems were assumed to play a key role in the formation of persister cells in Escherichia coli based on the observation that successive deletions of TA systems decreased persistence frequency. In addition, the model proposed that stochastic fluctuations of (p)ppGpp levels are the basis for triggering activation of TA systems. Cells in which TA systems are activated are thought to enter a dormancy state and therefore survive the antibiotic treatment. Using independently constructed strains and newly designed fluorescent reporters, we reassessed the roles of TA modules in persistence both at the population and single-cell levels. Our data confirm that the deletion of 10 TA systems does not affect persistence to ofloxacin or ampicillin. Moreover, microfluidic experiments performed with a strain reporting the induction of the yefM-yoeB TA system allowed the observation of a small number of type II persister cells that resume growth after removal of ampicillin. However, we were unable to establish a correlation between high fluorescence and persistence, since the fluorescence of persister cells was comparable to that of the bulk of the population and none of the cells showing high fluorescence were able to resume growth upon removal of the antibiotic. Altogether, these data show that there is no direct link between induction of TA systems and persistence to antibiotics.IMPORTANCE Within a growing bacterial population, a small subpopulation of cells is able to survive antibiotic treatment by entering a transient state of dormancy referred to as persistence. Persistence is thought to be the cause of relapsing bacterial infections and is a major public health concern. Type II toxin-antitoxin systems are small modules composed of a toxic protein and an antitoxin protein counteracting the toxin activity. These systems were thought to be pivotal players in persistence until recent developments in the field. Our results demonstrate that previous influential reports had technical flaws and that there is no direct link between induction of TA systems and persistence to antibiotics.
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Harms A, Brodersen DE, Mitarai N, Gerdes K. Toxins, Targets, and Triggers: An Overview of Toxin-Antitoxin Biology. Mol Cell 2018; 70:768-784. [PMID: 29398446 DOI: 10.1016/j.molcel.2018.01.003] [Citation(s) in RCA: 398] [Impact Index Per Article: 66.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2017] [Revised: 11/06/2017] [Accepted: 01/02/2018] [Indexed: 12/01/2022]
Abstract
Bacterial toxin-antitoxin (TA) modules are abundant genetic elements that encode a toxin protein capable of inhibiting cell growth and an antitoxin that counteracts the toxin. The majority of toxins are enzymes that interfere with translation or DNA replication, but a wide variety of molecular activities and cellular targets have been described. Antitoxins are proteins or RNAs that often control their cognate toxins through direct interactions and, in conjunction with other signaling elements, through transcriptional and translational regulation of TA module expression. Three major biological functions of TA modules have been discovered, post-segregational killing ("plasmid addiction"), abortive infection (bacteriophage immunity through altruistic suicide), and persister formation (antibiotic tolerance through dormancy). In this review, we summarize the current state of the field and highlight how multiple levels of regulation shape the conditions of toxin activation to achieve the different biological functions of TA modules.
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Affiliation(s)
- Alexander Harms
- Centre for Bacterial Stress Response and Persistence, Department of Biology, University of Copenhagen, 2200 Copenhagen, Denmark.
| | - Ditlev Egeskov Brodersen
- Centre for Bacterial Stress Response and Persistence, Department of Biology, University of Copenhagen, 2200 Copenhagen, Denmark; Department of Molecular Biology and Genetics, Aarhus University, 8000 Aarhus, Denmark
| | - Namiko Mitarai
- Centre for Bacterial Stress Response and Persistence, Department of Biology, University of Copenhagen, 2200 Copenhagen, Denmark; Niels Bohr Institute, Department of Physics, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Kenn Gerdes
- Centre for Bacterial Stress Response and Persistence, Department of Biology, University of Copenhagen, 2200 Copenhagen, Denmark.
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Identification of novel mazEF/pemIK family toxin-antitoxin loci and their distribution in the Staphylococcus genus. Sci Rep 2017; 7:13462. [PMID: 29044211 PMCID: PMC5647390 DOI: 10.1038/s41598-017-13857-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2017] [Accepted: 10/02/2017] [Indexed: 11/15/2022] Open
Abstract
The versatile roles of toxin-antitoxin (TA) systems in bacterial physiology and pathogenesis have been investigated for more than three decades. Diverse TA loci in Bacteria and Archaea have been identified in genome-wide studies. The advent of massive parallel sequencing has substantially expanded the number of known bacterial genomic sequences over the last 5 years. In staphylococci, this has translated into an impressive increase from a few tens to a several thousands of available genomes, which has allowed us for the re-evalution of prior conclusions. In this study, we analysed the distribution of mazEF/pemIK family TA system operons in available staphylococcal genomes and their prevalence in mobile genetic elements. 10 novel mazEF/pemIK homologues were identified, each with a corresponding toxin that plays a potentially different and undetermined physiological role. A detailed characterisation of these TA systems would be exceptionally useful. Of particular interest are those associated with an SCCmec mobile genetic element (responsible for multidrug resistance transmission) or representing the joint horizontal transfer of TA systems and determinants of vancomycin resistance from enterococci. The involvement of TA systems in maintaining mobile genetic elements and the associations between novel mazEF/pemIK loci and those which carry drug resistance genes highlight their potential medical importance.
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Pilla G, McVicker G, Tang CM. Genetic plasticity of the Shigella virulence plasmid is mediated by intra- and inter-molecular events between insertion sequences. PLoS Genet 2017; 13:e1007014. [PMID: 28945748 PMCID: PMC5629016 DOI: 10.1371/journal.pgen.1007014] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2017] [Revised: 10/05/2017] [Accepted: 09/08/2017] [Indexed: 11/18/2022] Open
Abstract
Acquisition of a single copy, large virulence plasmid, pINV, led to the emergence of Shigella spp. from Escherichia coli. The plasmid encodes a Type III secretion system (T3SS) on a 30 kb pathogenicity island (PAI), and is maintained in a bacterial population through a series of toxin:antitoxin (TA) systems which mediate post-segregational killing (PSK). The T3SS imposes a significant cost on the bacterium, and strains which have lost the plasmid and/or genes encoding the T3SS grow faster than wild-type strains in the laboratory, and fail to bind the indicator dye Congo Red (CR). Our aim was to define the molecular events in Shigella flexneri that cause loss of Type III secretion (T3S), and to examine whether TA systems exert positional effects on pINV. During growth at 37°C, we found that deletions of regions of the plasmid including the PAI lead to the emergence of CR-negative colonies; deletions occur through intra-molecular recombination events between insertion sequences (ISs) flanking the PAI. Furthermore, by repositioning MvpAT (which belongs to the VapBC family of TA systems) near the PAI, we demonstrate that the location of this TA system alters the rearrangements that lead to loss of T3S, indicating that MvpAT acts both globally (by reducing loss of pINV through PSK) as well as locally (by preventing loss of adjacent sequences). During growth at environmental temperatures, we show for the first time that pINV spontaneously integrates into different sites in the chromosome, and this is mediated by inter-molecular events involving IS1294. Integration leads to reduced PAI gene expression and impaired secretion through the T3SS, while excision of pINV from the chromosome restores T3SS function. Therefore, pINV integration provides a reversible mechanism for Shigella to circumvent the metabolic burden imposed by pINV. Intra- and inter-molecular events between ISs, which are abundant in Shigella spp., mediate plasticity of S. flexneri pINV.
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Affiliation(s)
- Giulia Pilla
- Sir William Dunn School of Pathology, University of Oxford, Oxford, United Kingdom
| | - Gareth McVicker
- Sir William Dunn School of Pathology, University of Oxford, Oxford, United Kingdom
| | - Christoph M. Tang
- Sir William Dunn School of Pathology, University of Oxford, Oxford, United Kingdom
- * E-mail:
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Klimina KM, Poluektova EU, Danilenko VN. Bacterial toxin–antitoxin systems: Properties, functional significance, and possibility of use (Review). APPL BIOCHEM MICRO+ 2017. [DOI: 10.1134/s0003683817050076] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Díaz-Orejas R, Espinosa M, Yeo CC. The Importance of the Expendable: Toxin-Antitoxin Genes in Plasmids and Chromosomes. Front Microbiol 2017; 8:1479. [PMID: 28824602 PMCID: PMC5543033 DOI: 10.3389/fmicb.2017.01479] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2017] [Accepted: 07/24/2017] [Indexed: 02/01/2023] Open
Abstract
Toxin–antitoxin (TA) genes were first reported in plasmids and were considered expendable genetic cassettes involved in the stable maintenance of the plasmid replicon by interfering with growth and/or viability of bacteria in which the plasmid was lost. TAs were later found in bacterial chromosomes and also in integrated mobile genetic elements; they were proposed to be involved in the bacterial response to stressful situations. At present, 100s of TAs have been identified and classified in up to six families (I to VI), with those belonging to the type II (constituted by two protein components) being the most studied. Based on well-characterized examples of several type II TAs, we discuss in this review that irrespective of their locations in plasmids or chromosomes, TAs functionally overlap as indicated by: (i) in both locations they can mediate the maintenance of genetic elements to which they are physical linked, and (ii) they can induce persistence or virulence in response to stress situations. Examples of functional confluences in homologous TA systems with different locations are also given. We also consider whether the physiological role of TAs is due to their genetic organization as operons or to their inherent properties, like the short lifespan of the antitoxin component.
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Affiliation(s)
- Ramón Díaz-Orejas
- Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas (CSIC)Madrid, Spain
| | - Manuel Espinosa
- Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas (CSIC)Madrid, Spain
| | - Chew Chieng Yeo
- Faculty of Medicine, Biomedical Research Centre, Universiti Sultan Zainal AbidinKuala Terengganu, Malaysia
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Ramisetty BCM, Santhosh RS. Endoribonuclease type II toxin-antitoxin systems: functional or selfish? MICROBIOLOGY-SGM 2017; 163:931-939. [PMID: 28691660 DOI: 10.1099/mic.0.000487] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Most bacterial genomes have multiple type II toxin-antitoxin systems (TAs) that encode two proteins which are referred to as a toxin and an antitoxin. Toxins inhibit a cellular process, while the interaction of the antitoxin with the toxin attenuates the toxin's activity. Endoribonuclease-encoding TAs cleave RNA in a sequence-dependent fashion, resulting in translational inhibition. To account for their prevalence and retention by bacterial genomes, TAs are credited with clinically significant phenomena, such as bacterial programmed cell death, persistence, biofilms and anti-addiction to plasmids. However, the programmed cell death and persistence hypotheses have been challenged because of conceptual, methodological and/or strain issues. In an alternative view, chromosomal TAs seem to be retained by virtue of addiction at two levels: via a poison-antidote combination (TA proteins) and via transcriptional reprogramming of the downstream core gene (due to integration). Any perturbation in the chromosomal TA operons could cause fitness loss due to polar effects on the downstream genes and hence be detrimental under natural conditions. The endoribonucleases encoding chromosomal TAs are most likely selfish DNA as they are retained by bacterial genomes, even though TAs do not confer a direct advantage via the TA proteins. TAs are likely used by various replicons as 'genetic arms' that allow the maintenance of themselves and associated genetic elements. TAs seem to be the 'selfish arms' that make the best use of the 'arms race' between bacterial genomes and plasmids.
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