1
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Wang R, Xu Q, Wu Z, Li J, Guo H, Liao T, Shi Y, Yuan L, Gao H, Yang R, Shi Z, Li F. The structural basis of the activation and inhibition of DSR2 NADase by phage proteins. Nat Commun 2024; 15:6185. [PMID: 39039073 PMCID: PMC11263360 DOI: 10.1038/s41467-024-50410-0] [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: 01/29/2024] [Accepted: 07/09/2024] [Indexed: 07/24/2024] Open
Abstract
DSR2, a Sir2 domain-containing protein, protects bacteria from phage infection by hydrolyzing NAD+. The enzymatic activity of DSR2 is triggered by the SPR phage tail tube protein (TTP), while suppressed by the SPbeta phage-encoded DSAD1 protein, enabling phages to evade the host defense. However, the molecular mechanisms of activation and inhibition of DSR2 remain elusive. Here, we report the cryo-EM structures of apo DSR2, DSR2-TTP-NAD+ and DSR2-DSAD1 complexes. DSR2 assembles into a head-to-head tetramer mediated by its Sir2 domain. The C-terminal helical regions of DSR2 constitute four partner-binding cavities with opened and closed conformation. Two TTP molecules bind to two of the four C-terminal cavities, inducing conformational change of Sir2 domain to activate DSR2. Furthermore, DSAD1 competes with the activator for binding to the C-terminal cavity of DSR2, effectively suppressing its enzymatic activity. Our results provide the mechanistic insights into the DSR2-mediated anti-phage defense system and DSAD1-dependent phage immune evasion.
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Affiliation(s)
- Ruiwen Wang
- MOE Key Laboratory of Rare Pediatric Diseases, Center for Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan, China
| | - Qi Xu
- Zhejiang Key Laboratory of Structural Biology, School of Life Sciences, Westlake University, Hangzhou, Zhejiang, China
- Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, Zhejiang, China
| | - Zhuoxi Wu
- MOE Key Laboratory of Rare Pediatric Diseases, Center for Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan, China
| | - Jialu Li
- Zhejiang Key Laboratory of Structural Biology, School of Life Sciences, Westlake University, Hangzhou, Zhejiang, China
- Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, Zhejiang, China
| | - Hao Guo
- MOE Key Laboratory of Rare Pediatric Diseases, Center for Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan, China
| | - Tianzhui Liao
- MOE Key Laboratory of Rare Pediatric Diseases, Center for Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan, China
| | - Yuan Shi
- Zhejiang Key Laboratory of Structural Biology, School of Life Sciences, Westlake University, Hangzhou, Zhejiang, China
- Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, Zhejiang, China
| | - Ling Yuan
- MOE Key Laboratory of Rare Pediatric Diseases, Center for Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan, China
| | - Haishan Gao
- Zhejiang Key Laboratory of Structural Biology, School of Life Sciences, Westlake University, Hangzhou, Zhejiang, China
- Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, Zhejiang, China
| | - Rong Yang
- State Key Laboratory of Developmental Biology of Freshwater Fish, Engineering Research Center of Polyploid Fish Reproduction and Breeding of the State Education Ministry, College of Life Sciences, Hunan Normal University, Changsha, Hunan, China.
| | - Zhubing Shi
- Zhejiang Key Laboratory of Structural Biology, School of Life Sciences, Westlake University, Hangzhou, Zhejiang, China.
- Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, Zhejiang, China.
| | - Faxiang Li
- MOE Key Laboratory of Rare Pediatric Diseases, Center for Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan, China.
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2
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Bullen NP, Johnson CN, Andersen SE, Arya G, Marotta SR, Lee YJ, Weigele PR, Whitney JC, Duerkop BA. An enterococcal phage protein broadly inhibits type IV restriction enzymes involved in antiphage defense. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.11.16.567456. [PMID: 38014348 PMCID: PMC10680825 DOI: 10.1101/2023.11.16.567456] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2023]
Abstract
The prevalence of multidrug resistant (MDR) bacterial infections continues to rise as the development of antibiotics needed to combat these infections remains stagnant. MDR enterococci are a major contributor to this crisis. A potential therapeutic approach for combating MDR enterococci is bacteriophage (phage) therapy, which uses lytic viruses to infect and kill pathogenic bacteria. While phages that lyse some strains of MDR enterococci have been identified, other strains display high levels of resistance and the mechanisms underlying this resistance are poorly defined. Here, we use a CRISPR interference (CRISPRi) screen to identify a genetic locus found on a mobilizable plasmid from Enterococcus faecalis involved in phage resistance. This locus encodes a putative serine recombinase followed by a Type IV restriction enzyme (TIV-RE) that we show restricts the replication of phage phi47 in E. faecalis . We further find that phi47 evolves to overcome restriction by acquiring a missense mutation in a TIV-RE inhibitor protein. We show that this inhibitor, termed type IV restriction inhibiting factor A ( tifA ), binds and inactivates diverse TIV-REs. Overall, our findings advance our understanding of phage defense in drug-resistant E. faecalis and provide mechanistic insight into how phages evolve to overcome antiphage defense systems.
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Affiliation(s)
- Nathan P. Bullen
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON, Canada, L8S 4L8
- Michael DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, ON, Canada
| | - Cydney N. Johnson
- Department of Immunology and Microbiology, University of Colorado School – Anschutz Medical Campus, School of Medicine, Aurora, CO, USA, 80045
| | - Shelby E. Andersen
- Department of Immunology and Microbiology, University of Colorado School – Anschutz Medical Campus, School of Medicine, Aurora, CO, USA, 80045
| | - Garima Arya
- Department of Immunology and Microbiology, University of Colorado School – Anschutz Medical Campus, School of Medicine, Aurora, CO, USA, 80045
| | - Sonia R. Marotta
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON, Canada, L8S 4L8
- Michael DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, ON, Canada
| | - Yan-Jiun Lee
- Research Department, New England Biolabs, Ipswich, MA, USA, 01938
| | - Peter R. Weigele
- Research Department, New England Biolabs, Ipswich, MA, USA, 01938
| | - John C. Whitney
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON, Canada, L8S 4L8
- Michael DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, ON, Canada
| | - Breck A. Duerkop
- Department of Immunology and Microbiology, University of Colorado School – Anschutz Medical Campus, School of Medicine, Aurora, CO, USA, 80045
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3
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Carabias A, Camara-Wilpert S, Mestre MR, Lopéz-Méndez B, Hendriks IA, Zhao R, Pape T, Fuglsang A, Luk SHC, Nielsen ML, Pinilla-Redondo R, Montoya G. Retron-Eco1 assembles NAD +-hydrolyzing filaments that provide immunity against bacteriophages. Mol Cell 2024; 84:2185-2202.e12. [PMID: 38788717 DOI: 10.1016/j.molcel.2024.05.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2023] [Revised: 03/15/2024] [Accepted: 05/01/2024] [Indexed: 05/26/2024]
Abstract
Retrons are toxin-antitoxin systems protecting bacteria against bacteriophages via abortive infection. The Retron-Eco1 antitoxin is formed by a reverse transcriptase (RT) and a non-coding RNA (ncRNA)/multi-copy single-stranded DNA (msDNA) hybrid that neutralizes an uncharacterized toxic effector. Yet, the molecular mechanisms underlying phage defense remain unknown. Here, we show that the N-glycosidase effector, which belongs to the STIR superfamily, hydrolyzes NAD+ during infection. Cryoelectron microscopy (cryo-EM) analysis shows that the msDNA stabilizes a filament that cages the effector in a low-activity state in which ADPr, a NAD+ hydrolysis product, is covalently linked to the catalytic E106 residue. Mutations shortening the msDNA induce filament disassembly and the effector's toxicity, underscoring the msDNA role in immunity. Furthermore, we discovered a phage-encoded Retron-Eco1 inhibitor (U56) that binds ADPr, highlighting the intricate interplay between retron systems and phage evolution. Our work outlines the structural basis of Retron-Eco1 defense, uncovering ADPr's pivotal role in immunity.
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Affiliation(s)
- Arturo Carabias
- Structural Molecular Biology Group, Novo Nordisk Foundation Centre for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen, Denmark.
| | - Sarah Camara-Wilpert
- Section of Microbiology, Department of Biology, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Mario Rodríguez Mestre
- Section of Microbiology, Department of Biology, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Blanca Lopéz-Méndez
- Protein Purification and Characterization Facility, Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, 2200 Copenhagen, Denmark
| | - Ivo A Hendriks
- Proteomics Department, Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, 2200 Copenhagen, Denmark
| | - Ruiliang Zhao
- Section of Microbiology, Department of Biology, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Tillmann Pape
- Structural Molecular Biology Group, Novo Nordisk Foundation Centre for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen, Denmark; Core Facility for Integrated Microscopy (CFIM), Faculty of Health and Medical Sciences, University of Copenhagen, 2200 Copenhagen, Denmark
| | - Anders Fuglsang
- Structural Molecular Biology Group, Novo Nordisk Foundation Centre for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen, Denmark
| | - Sean Hoi-Ching Luk
- Structural Molecular Biology Group, Novo Nordisk Foundation Centre for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen, Denmark
| | - Michael L Nielsen
- Proteomics Department, Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, 2200 Copenhagen, Denmark
| | - Rafael Pinilla-Redondo
- Section of Microbiology, Department of Biology, University of Copenhagen, 2100 Copenhagen, Denmark.
| | - Guillermo Montoya
- Structural Molecular Biology Group, Novo Nordisk Foundation Centre for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen, Denmark.
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4
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Saunier M, Fortier LC, Soutourina O. RNA-based regulation in bacteria-phage interactions. Anaerobe 2024; 87:102851. [PMID: 38583547 DOI: 10.1016/j.anaerobe.2024.102851] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2023] [Revised: 03/24/2024] [Accepted: 04/02/2024] [Indexed: 04/09/2024]
Abstract
Interactions of bacteria with their viruses named bacteriophages or phages shape the bacterial genome evolution and contribute to the diversity of phages. RNAs have emerged as key components of several anti-phage defense systems in bacteria including CRISPR-Cas, toxin-antitoxin and abortive infection. Frequent association with mobile genetic elements and interplay between different anti-phage defense systems are largely discussed. Newly discovered defense systems such as retrons and CBASS include RNA components. RNAs also perform their well-recognized regulatory roles in crossroad of phage-bacteria regulatory networks. Both regulatory and defensive function can be sometimes attributed to the same RNA molecules including CRISPR RNAs. This review presents the recent advances on the role of RNAs in the bacteria-phage interactions with a particular focus on clostridial species including an important human pathogen, Clostridioides difficile.
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Affiliation(s)
- Marion Saunier
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198, Gif-sur-Yvette, France; Department of Microbiology and Infectious Diseases, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, QC, Canada
| | - Louis-Charles Fortier
- Department of Microbiology and Infectious Diseases, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, QC, Canada
| | - Olga Soutourina
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198, Gif-sur-Yvette, France; Institut Universitaire de France (IUF), Paris, France.
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5
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Mayo-Muñoz D, Pinilla-Redondo R, Camara-Wilpert S, Birkholz N, Fineran PC. Inhibitors of bacterial immune systems: discovery, mechanisms and applications. Nat Rev Genet 2024; 25:237-254. [PMID: 38291236 DOI: 10.1038/s41576-023-00676-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/07/2023] [Indexed: 02/01/2024]
Abstract
To contend with the diversity and ubiquity of bacteriophages and other mobile genetic elements, bacteria have developed an arsenal of immune defence mechanisms. Bacterial defences include CRISPR-Cas, restriction-modification and a growing list of mechanistically diverse systems, which constitute the bacterial 'immune system'. As a response, bacteriophages and mobile genetic elements have evolved direct and indirect mechanisms to circumvent or block bacterial defence pathways and ensure successful infection. Recent advances in methodological and computational approaches, as well as the increasing availability of genome sequences, have boosted the discovery of direct inhibitors of bacterial defence systems. In this Review, we discuss methods for the discovery of direct inhibitors, their diverse mechanisms of action and perspectives on their emerging applications in biotechnology and beyond.
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Affiliation(s)
- David Mayo-Muñoz
- Department of Microbiology and Immunology, University of Otago, Dunedin, New Zealand
- Genetics Otago, University of Otago, Dunedin, New Zealand
- Maurice Wilkins Centre for Molecular Biodiscovery, University of Otago, Dunedin, New Zealand
| | - Rafael Pinilla-Redondo
- Department of Microbiology and Immunology, University of Otago, Dunedin, New Zealand.
- Section of Microbiology, University of Copenhagen, Copenhagen, Denmark.
| | | | - Nils Birkholz
- Department of Microbiology and Immunology, University of Otago, Dunedin, New Zealand
- Genetics Otago, University of Otago, Dunedin, New Zealand
- Maurice Wilkins Centre for Molecular Biodiscovery, University of Otago, Dunedin, New Zealand
- Bioprotection Aotearoa, University of Otago, Dunedin, New Zealand
| | - Peter C Fineran
- Department of Microbiology and Immunology, University of Otago, Dunedin, New Zealand.
- Genetics Otago, University of Otago, Dunedin, New Zealand.
- Maurice Wilkins Centre for Molecular Biodiscovery, University of Otago, Dunedin, New Zealand.
- Bioprotection Aotearoa, University of Otago, Dunedin, New Zealand.
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6
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Guegler CK, Teodoro GIC, Srikant S, Chetlapalli K, Doering CR, Ghose DA, Laub MT. A phage-encoded RNA-binding protein inhibits the antiviral activity of a toxin-antitoxin system. Nucleic Acids Res 2024; 52:1298-1312. [PMID: 38117986 PMCID: PMC10853763 DOI: 10.1093/nar/gkad1207] [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: 06/23/2023] [Revised: 12/02/2023] [Accepted: 12/06/2023] [Indexed: 12/22/2023] Open
Abstract
Bacteria harbor diverse mechanisms to defend themselves against their viral predators, bacteriophages. In response, phages can evolve counter-defense systems, most of which are poorly understood. In T4-like phages, the gene tifA prevents bacterial defense by the type III toxin-antitoxin (TA) system toxIN, but the mechanism by which TifA inhibits ToxIN remains unclear. Here, we show that TifA directly binds both the endoribonuclease ToxN and RNA, leading to the formation of a high molecular weight ribonucleoprotein complex in which ToxN is inhibited. The RNA binding activity of TifA is necessary for its interaction with and inhibition of ToxN. Thus, we propose that TifA inhibits ToxN during phage infection by trapping ToxN on cellular RNA, particularly the abundant 16S rRNA, thereby preventing cleavage of phage transcripts. Taken together, our results reveal a novel mechanism underlying inhibition of a phage-defensive RNase toxin by a small, phage-encoded protein.
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Affiliation(s)
- Chantal K Guegler
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
- Department of Genetics, Harvard Medical School, Boston, MA 02115, USA
| | - Gabriella I C Teodoro
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Sriram Srikant
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Keerthana Chetlapalli
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Christopher R Doering
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Dia A Ghose
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Michael T Laub
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
- Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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7
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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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8
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Yirmiya E, Leavitt A, Lu A, Ragucci AE, Avraham C, Osterman I, Garb J, Antine SP, Mooney SE, Hobbs SJ, Kranzusch PJ, Amitai G, Sorek R. Phages overcome bacterial immunity via diverse anti-defence proteins. Nature 2024; 625:352-359. [PMID: 37992756 DOI: 10.1038/s41586-023-06869-w] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2023] [Accepted: 11/14/2023] [Indexed: 11/24/2023]
Abstract
It was recently shown that bacteria use, apart from CRISPR-Cas and restriction systems, a considerable diversity of phage resistance systems1-4, but it is largely unknown how phages cope with this multilayered bacterial immunity. Here we analysed groups of closely related Bacillus phages that showed differential sensitivity to bacterial defence systems, and discovered four distinct families of anti-defence proteins that inhibit the Gabija, Thoeris and Hachiman systems. We show that these proteins Gad1, Gad2, Tad2 and Had1 efficiently cancel the defensive activity when co-expressed with the respective defence system or introduced into phage genomes. Homologues of these anti-defence proteins are found in hundreds of phages that infect taxonomically diverse bacterial species. We show that the anti-Gabija protein Gad1 blocks the ability of the Gabija defence complex to cleave phage-derived DNA. Our data further reveal that the anti-Thoeris protein Tad2 is a 'sponge' that sequesters the immune signalling molecules produced by Thoeris TIR-domain proteins in response to phage infection. Our results demonstrate that phages encode an arsenal of anti-defence proteins that can disable a variety of bacterial defence mechanisms.
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Affiliation(s)
- Erez Yirmiya
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, Israel
| | - Azita Leavitt
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, Israel
| | - Allen Lu
- Department of Microbiology, Harvard Medical School, Boston, MA, USA
- Department of Cancer Immunology and Virology, Dana-Farber Cancer Institute, Boston, MA, USA
| | - Adelyn E Ragucci
- Department of Microbiology, Harvard Medical School, Boston, MA, USA
- Department of Cancer Immunology and Virology, Dana-Farber Cancer Institute, Boston, MA, USA
| | - Carmel Avraham
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, Israel
| | - Ilya Osterman
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, Israel
| | - Jeremy Garb
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, Israel
| | - Sadie P Antine
- Department of Microbiology, Harvard Medical School, Boston, MA, USA
- Department of Cancer Immunology and Virology, Dana-Farber Cancer Institute, Boston, MA, USA
| | - Sarah E Mooney
- Department of Microbiology, Harvard Medical School, Boston, MA, USA
- Department of Cancer Immunology and Virology, Dana-Farber Cancer Institute, Boston, MA, USA
| | - Samuel J Hobbs
- Department of Microbiology, Harvard Medical School, Boston, MA, USA
- Department of Cancer Immunology and Virology, Dana-Farber Cancer Institute, Boston, MA, USA
| | - Philip J Kranzusch
- Department of Microbiology, Harvard Medical School, Boston, MA, USA
- Department of Cancer Immunology and Virology, Dana-Farber Cancer Institute, Boston, MA, USA
- Parker Institute for Cancer Immunotherapy at Dana-Farber Cancer Institute, Boston, MA, USA
| | - Gil Amitai
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, Israel.
| | - Rotem Sorek
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, Israel.
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9
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Patel KM, Seed KD. Sporadic phage defense in epidemic Vibrio cholerae mediated by the toxin-antitoxin system DarTG is countered by a phage-encoded antitoxin mimic. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.12.14.571748. [PMID: 38168179 PMCID: PMC10760071 DOI: 10.1101/2023.12.14.571748] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2024]
Abstract
Bacteria and their viral predators (phages) are constantly evolving to subvert one another. Many bacterial immune systems that inhibit phages are encoded on mobile genetic elements that can be horizontally transmitted to diverse bacteria. Despite the pervasive appearance of immune systems in bacteria, it is not often known if these immune systems function against phages that the host encounters in nature. Additionally, there are limited examples demonstrating how these phages counter-adapt to such immune systems. Here, we identify clinical isolates of the global pathogen Vibrio cholerae harboring a novel genetic element encoding the bacterial immune system DarTG and reveal the immune system's impact on the co-circulating lytic phage ICP1. We show that DarTG inhibits ICP1 genome replication, thus preventing ICP1 plaquing. We further characterize the conflict between DarTG-mediated defense and ICP1 by identifying an ICP1-encoded protein that counters DarTG and allows ICP1 progeny production. Finally, we identify this protein as a functional antitoxin that abrogates the toxin DarT likely through direct interactions. Following the detection of the DarTG system in clinical V. cholerae isolates, we observed a rise in ICP1 isolates with the functional antitoxin. These data highlight the use of surveillance of V. cholerae and its lytic phages to understand the co-evolutionary arms race between bacteria and their phages in nature.
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Affiliation(s)
- Kishen M Patel
- Infectious Diseases and Immunity Graduate Group, School of Public Health, University of California, Berkeley, Berkeley, CA, USA
- Department of Plant and Microbial Biology, University of California, Berkeley, Berkeley, California, USA
| | - Kimberley D Seed
- Department of Plant and Microbial Biology, University of California, Berkeley, Berkeley, California, USA
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10
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Camara-Wilpert S, Mayo-Muñoz D, Russel J, Fagerlund RD, Madsen JS, Fineran PC, Sørensen SJ, Pinilla-Redondo R. Bacteriophages suppress CRISPR-Cas immunity using RNA-based anti-CRISPRs. Nature 2023; 623:601-607. [PMID: 37853129 PMCID: PMC10651486 DOI: 10.1038/s41586-023-06612-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2022] [Accepted: 09/05/2023] [Indexed: 10/20/2023]
Abstract
Many bacteria use CRISPR-Cas systems to combat mobile genetic elements, such as bacteriophages and plasmids1. In turn, these invasive elements have evolved anti-CRISPR proteins to block host immunity2,3. Here we unveil a distinct type of CRISPR-Cas Inhibition strategy that is based on small non-coding RNA anti-CRISPRs (Racrs). Racrs mimic the repeats found in CRISPR arrays and are encoded in viral genomes as solitary repeat units4. We show that a prophage-encoded Racr strongly inhibits the type I-F CRISPR-Cas system by interacting specifically with Cas6f and Cas7f, resulting in the formation of an aberrant Cas subcomplex. We identified Racr candidates for almost all CRISPR-Cas types encoded by a diverse range of viruses and plasmids, often in the genetic context of other anti-CRISPR genes5. Functional testing of nine candidates spanning the two CRISPR-Cas classes confirmed their strong immune inhibitory function. Our results demonstrate that molecular mimicry of CRISPR repeats is a widespread anti-CRISPR strategy, which opens the door to potential biotechnological applications6.
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Affiliation(s)
| | - David Mayo-Muñoz
- Department of Microbiology and Immunology, University of Otago, Dunedin, New Zealand
- Genetics Otago, University of Otago, Dunedin, New Zealand
- Maurice Wilkins Centre for Molecular Biodiscovery, University of Otago, Dunedin, New Zealand
| | - Jakob Russel
- Section of Microbiology, University of Copenhagen, Copenhagen, Denmark
| | - Robert D Fagerlund
- Department of Microbiology and Immunology, University of Otago, Dunedin, New Zealand
- Genetics Otago, University of Otago, Dunedin, New Zealand
- Maurice Wilkins Centre for Molecular Biodiscovery, University of Otago, Dunedin, New Zealand
- Bioprotection Aotearoa, University of Otago, Dunedin, New Zealand
| | - Jonas S Madsen
- Section of Microbiology, University of Copenhagen, Copenhagen, Denmark
| | - Peter C Fineran
- Department of Microbiology and Immunology, University of Otago, Dunedin, New Zealand.
- Genetics Otago, University of Otago, Dunedin, New Zealand.
- Maurice Wilkins Centre for Molecular Biodiscovery, University of Otago, Dunedin, New Zealand.
- Bioprotection Aotearoa, University of Otago, Dunedin, New Zealand.
| | - Søren J Sørensen
- Section of Microbiology, University of Copenhagen, Copenhagen, Denmark
| | - Rafael Pinilla-Redondo
- Section of Microbiology, University of Copenhagen, Copenhagen, Denmark.
- Department of Microbiology and Immunology, University of Otago, Dunedin, New Zealand.
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11
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Georjon H, Bernheim A. The highly diverse antiphage defence systems of bacteria. Nat Rev Microbiol 2023; 21:686-700. [PMID: 37460672 DOI: 10.1038/s41579-023-00934-x] [Citation(s) in RCA: 57] [Impact Index Per Article: 57.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/15/2023] [Indexed: 09/14/2023]
Abstract
Bacteria and their viruses have coevolved for billions of years. This ancient and still ongoing arms race has led bacteria to develop a vast antiphage arsenal. The development of high-throughput screening methods expanded our knowledge of defence systems from a handful to more than a hundred systems, unveiling many different molecular mechanisms. These findings reveal that bacterial immunity is much more complex than previously thought. In this Review, we explore recently discovered bacterial antiphage defence systems, with a particular focus on their molecular diversity, and discuss the ecological and evolutionary drivers and implications of the existing diversity of antiphage defence mechanisms.
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Affiliation(s)
- Héloïse Georjon
- Molecular Diversity of Microbes Lab, Institut Pasteur, Université Paris Cité, INSERM, Paris, France
| | - Aude Bernheim
- Molecular Diversity of Microbes Lab, Institut Pasteur, Université Paris Cité, INSERM, Paris, France.
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12
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Kelly A, Went SC, Mariano G, Shaw LP, Picton DM, Duffner SJ, Coates I, Herdman-Grant R, Gordeeva J, Drobiazko A, Isaev A, Lee YJ, Luyten Y, Morgan RD, Weigele P, Severinov K, Wenner N, Hinton JCD, Blower TR. Diverse Durham collection phages demonstrate complex BREX defense responses. Appl Environ Microbiol 2023; 89:e0062323. [PMID: 37668405 PMCID: PMC10537673 DOI: 10.1128/aem.00623-23] [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: 04/13/2023] [Accepted: 07/10/2023] [Indexed: 09/06/2023] Open
Abstract
Bacteriophages (phages) outnumber bacteria ten-to-one and cause infections at a rate of 1025 per second. The ability of phages to reduce bacterial populations makes them attractive alternative antibacterials for use in combating the rise in antimicrobial resistance. This effort may be hindered due to bacterial defenses such as Bacteriophage Exclusion (BREX) that have arisen from the constant evolutionary battle between bacteria and phages. For phages to be widely accepted as therapeutics in Western medicine, more must be understood about bacteria-phage interactions and the outcomes of bacterial phage defense. Here, we present the annotated genomes of 12 novel bacteriophage species isolated from water sources in Durham, UK, during undergraduate practical classes. The collection includes diverse species from across known phylogenetic groups. Comparative analyses of two novel phages from the collection suggest they may be founding members of a new genus. Using this Durham phage collection, we determined that particular BREX defense systems were likely to confer a varied degree of resistance against an invading phage. We concluded that the number of BREX target motifs encoded in the phage genome was not proportional to the degree of susceptibility. IMPORTANCE Bacteriophages have long been the source of tools for biotechnology that are in everyday use in molecular biology research laboratories worldwide. Phages make attractive new targets for the development of novel antimicrobials. While the number of phage genome depositions has increased in recent years, the expected bacteriophage diversity remains underrepresented. Here we demonstrate how undergraduates can contribute to the identification of novel phages and that a single City in England can provide ample phage diversity and the opportunity to find novel technologies. Moreover, we demonstrate that the interactions and intricacies of the interplay between bacterial phage defense systems such as Bacteriophage Exclusion (BREX) and phages are more complex than originally thought. Further work will be required in the field before the dynamic interactions between phages and bacterial defense systems are fully understood and integrated with novel phage therapies.
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Affiliation(s)
- Abigail Kelly
- Department of Biosciences, Durham University, Durham, UK
| | - Sam C. Went
- Department of Biosciences, Durham University, Durham, UK
| | - Giuseppina Mariano
- Microbes in Health and Disease Theme, Newcastle University Biosciences Institute, Newcastle University, Newcastle upon Tyne, UK
| | - Liam P. Shaw
- Department of Biosciences, Durham University, Durham, UK
- Department of Biology, University of Oxford, Oxford, UK
| | | | | | - Isabel Coates
- Department of Biosciences, Durham University, Durham, UK
| | | | - Julia Gordeeva
- Skolkovo Institute of Science and Technology, Moscow, Russia
| | - Alena Drobiazko
- Skolkovo Institute of Science and Technology, Moscow, Russia
| | - Artem Isaev
- Skolkovo Institute of Science and Technology, Moscow, Russia
| | - Yan-Jiun Lee
- New England Biolabs, Ipswich, Massachusetts, USA
| | | | | | | | | | - Nicolas Wenner
- Institute of Infection, Veterinary and Ecological Sciences, University of Liverpool, Liverpool, UK
| | - Jay C. D. Hinton
- Institute of Infection, Veterinary and Ecological Sciences, University of Liverpool, Liverpool, UK
| | - Tim R. Blower
- Department of Biosciences, Durham University, Durham, UK
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13
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Gao Z, Feng Y. Bacteriophage strategies for overcoming host antiviral immunity. Front Microbiol 2023; 14:1211793. [PMID: 37362940 PMCID: PMC10286901 DOI: 10.3389/fmicb.2023.1211793] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2023] [Accepted: 05/17/2023] [Indexed: 06/28/2023] Open
Abstract
Phages and their bacterial hosts together constitute a vast and diverse ecosystem. Facing the infection of phages, prokaryotes have evolved a wide range of antiviral mechanisms, and phages in turn have adopted multiple tactics to circumvent or subvert these mechanisms to survive. An in-depth investigation into the interaction between phages and bacteria not only provides new insight into the ancient coevolutionary conflict between them but also produces precision biotechnological tools based on anti-phage systems. Moreover, a more complete understanding of their interaction is also critical for the phage-based antibacterial measures. Compared to the bacterial antiviral mechanisms, studies into counter-defense strategies adopted by phages have been a little slow, but have also achieved important advances in recent years. In this review, we highlight the numerous intracellular immune systems of bacteria as well as the countermeasures employed by phages, with an emphasis on the bacteriophage strategies in response to host antiviral immunity.
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14
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Boss L, Kędzierska B. Bacterial Toxin-Antitoxin Systems' Cross-Interactions-Implications for Practical Use in Medicine and Biotechnology. Toxins (Basel) 2023; 15:380. [PMID: 37368681 DOI: 10.3390/toxins15060380] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2023] [Revised: 05/30/2023] [Accepted: 06/02/2023] [Indexed: 06/29/2023] Open
Abstract
Toxin-antitoxin (TA) systems are widely present in bacterial genomes. They consist of stable toxins and unstable antitoxins that are classified into distinct groups based on their structure and biological activity. TA systems are mostly related to mobile genetic elements and can be easily acquired through horizontal gene transfer. The ubiquity of different homologous and non-homologous TA systems within a single bacterial genome raises questions about their potential cross-interactions. Unspecific cross-talk between toxins and antitoxins of non-cognate modules may unbalance the ratio of the interacting partners and cause an increase in the free toxin level, which can be deleterious to the cell. Moreover, TA systems can be involved in broadly understood molecular networks as transcriptional regulators of other genes' expression or modulators of cellular mRNA stability. In nature, multiple copies of highly similar or identical TA systems are rather infrequent and probably represent a transition stage during evolution to complete insulation or decay of one of them. Nevertheless, several types of cross-interactions have been described in the literature to date. This implies a question of the possibility and consequences of the TA system cross-interactions, especially in the context of the practical application of the TA-based biotechnological and medical strategies, in which such TAs will be used outside their natural context, will be artificially introduced and induced in the new hosts. Thus, in this review, we discuss the prospective challenges of system cross-talks in the safety and effectiveness of TA system usage.
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Affiliation(s)
- Lidia Boss
- Department of Bacterial Molecular Genetics, Faculty of Biology, University of Gdańsk, 80-309 Gdańsk, Poland
| | - Barbara Kędzierska
- Department of Bacterial Molecular Genetics, Faculty of Biology, University of Gdańsk, 80-309 Gdańsk, Poland
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15
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Zhang Y, Song X, Chen C, Liu L, Xu Y, Zhang N, Huang W, Zheng J, Yuan W, Tang L, Lin Z. Structural insights of the toxin-antitoxin system VPA0770-VPA0769 in Vibrio parahaemolyticus. Int J Biol Macromol 2023:124755. [PMID: 37164131 DOI: 10.1016/j.ijbiomac.2023.124755] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2023] [Revised: 04/13/2023] [Accepted: 05/02/2023] [Indexed: 05/12/2023]
Abstract
Toxin-antitoxin (TA) systems are involved in both normal bacterial physiology and pathogenicity, including gene regulation, antibiotic resistance, and bacteria persistence under stressful environments. In pathogenic Vibrio parahaemolyticus, however, TA interaction and assembly remain largely unknown. In this work, we identified a new RES-Xre type II TA module, encoded by gene cluster vpa0770-vpa0769 on chromosome II of V. parahaemolyticus. Ectopic expression of the VPA0770 toxin rapidly arrests the growth of E. coli cells, which can be neutralized by co-expression of the VPA0769 antitoxin. To decipher the action mechanism, we determined the crystal structure of the VPA0770-VPA0769 TA complex. VPA0770 and VPA0769 proteins can assemble into two types of large complexes, a W-shaped hetero-hexamer and a donut-like hetero-dodecamer, in a concentration-dependent manner in solution. Disruption of the TA interface results in a loss of the antitoxic phenotype. The toxicity of the VPA0770 toxin, which harbors a NAD+-binding pocket, may be largely ascribed to its highly effective capability to degrade intracellular NAD+. Our study provides a structural basis for a better understanding of diverse molecular mechanisms employed by human pathogens.
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Affiliation(s)
- Yan Zhang
- School of Life Sciences, Tianjin University, Tianjin 300073, China
| | - Xiaojie Song
- School of Life Sciences, Tianjin University, Tianjin 300073, China
| | - Cheng Chen
- School of Life Sciences, Tianjin University, Tianjin 300073, China
| | - Lin Liu
- Guangdong Provincial Key Laboratory of Infectious Diseases and Molecular Immunopathology, Shantou University Medical College, Shantou 515041, China
| | - Yangyang Xu
- School of Life Sciences, Tianjin University, Tianjin 300073, China
| | - Ning Zhang
- School of Life Sciences, Tianjin University, Tianjin 300073, China
| | - Weidong Huang
- Department of Biochemistry and Molecular Biology, School of Basic Medicine, Ningxia Medical University, 750004, China
| | - Jun Zheng
- Faculty of Health Sciences, University of Macau, Macao
| | - Wensu Yuan
- School of Life Sciences, Tianjin University, Tianjin 300073, China.
| | - Le Tang
- Guangdong Provincial Key Laboratory of Infectious Diseases and Molecular Immunopathology, Shantou University Medical College, Shantou 515041, China.
| | - Zhi Lin
- School of Life Sciences, Tianjin University, Tianjin 300073, China.
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16
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Stokar-Avihail A, Fedorenko T, Hör J, Garb J, Leavitt A, Millman A, Shulman G, Wojtania N, Melamed S, Amitai G, Sorek R. Discovery of phage determinants that confer sensitivity to bacterial immune systems. Cell 2023; 186:1863-1876.e16. [PMID: 37030292 DOI: 10.1016/j.cell.2023.02.029] [Citation(s) in RCA: 38] [Impact Index Per Article: 38.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2022] [Revised: 01/09/2023] [Accepted: 02/20/2023] [Indexed: 04/10/2023]
Abstract
Over the past few years, numerous anti-phage defense systems have been discovered in bacteria. Although the mechanism of defense for some of these systems is understood, a major unanswered question is how these systems sense phage infection. To systematically address this question, we isolated 177 phage mutants that escape 15 different defense systems. In many cases, these escaper phages were mutated in the gene sensed by the defense system, enabling us to map the phage determinants that confer sensitivity to bacterial immunity. Our data identify specificity determinants of diverse retron systems and reveal phage-encoded triggers for multiple abortive infection systems. We find general themes in phage sensing and demonstrate that mechanistically diverse systems have converged to sense either the core replication machinery of the phage, phage structural components, or host takeover mechanisms. Combining our data with previous findings, we formulate key principles on how bacterial immune systems sense phage invaders.
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Affiliation(s)
- Avigail Stokar-Avihail
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Taya Fedorenko
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Jens Hör
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Jeremy Garb
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Azita Leavitt
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Adi Millman
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Gabriela Shulman
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Nicole Wojtania
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Sarah Melamed
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Gil Amitai
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Rotem Sorek
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 7610001, Israel.
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17
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Kelly A, Arrowsmith TJ, Went SC, Blower TR. Toxin-antitoxin systems as mediators of phage defence and the implications for abortive infection. Curr Opin Microbiol 2023; 73:102293. [PMID: 36958122 DOI: 10.1016/j.mib.2023.102293] [Citation(s) in RCA: 14] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2022] [Revised: 02/14/2023] [Accepted: 02/21/2023] [Indexed: 03/25/2023]
Abstract
Bacteria have evolved a broad range of defence mechanisms to protect against infection by their viral parasites, bacteriophages (phages). Toxin-antitoxin (TA) systems are small loci found throughout bacteria and archaea that in some cases provide phage defence. The recent explosion in phage defence system discovery has identified multiple novel TA systems with antiphage activity. Due to inherent toxicity, TA systems are thought to mediate abortive infection (Abi), wherein the host cell dies in response to phage infection, removing the phage, and protecting clonal siblings. Recent studies, however, have uncovered molecular mechanisms by which TA systems are activated by phages, how they mediate toxicity, and how phages escape the defences. These new models reveal dazzling complexity in phage-host interactions and provide further evidence that TA systems do not in all cases inherently perform classic Abi, suggesting an evolved conceptual definition is required.
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Affiliation(s)
- Abigail Kelly
- Department of Biosciences, Durham University, Stockton Road, Durham DH1 3LE, UK
| | - Tom J Arrowsmith
- Department of Biosciences, Durham University, Stockton Road, Durham DH1 3LE, UK
| | - Sam C Went
- Department of Biosciences, Durham University, Stockton Road, Durham DH1 3LE, UK
| | - Tim R Blower
- Department of Biosciences, Durham University, Stockton Road, Durham DH1 3LE, UK.
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18
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Naligama KN, Halmillawewa AP. Pectobacterium carotovorum Phage vB_PcaM_P7_Pc Is a New Member of the Genus Certrevirus. Microbiol Spectr 2022; 10:e0312622. [PMID: 36346243 PMCID: PMC9769974 DOI: 10.1128/spectrum.03126-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2022] [Accepted: 10/14/2022] [Indexed: 11/09/2022] Open
Abstract
Pectobacterium carotovorum is an economically important phytopathogen and has been identified as the major causative agent of bacterial soft rot in carrots. Control of this phytopathogen is vital to minimizing carrot harvest losses. As fully efficient control measures to successfully avoid the disease are unavailable, the phage-mediated biocontrol of the pathogen has recently gained scientific attention. In this study, we present a comprehensive characterization of the P. carotovorum phage vB_PcaM_P7_Pc (abbreviated as P7_Pc) that was isolated from infected carrot samples with characteristic soft rot symptoms, which were obtained from storage facilities at market places in Gampaha District, Sri Lanka. P7_Pc is a myovirus, and it exhibits growth characteristics of an exclusively lytic life cycle. It showed visible lysis against four of the tested P. carotovorum strains and one Pectobacterium aroidearum strain. This phage also showed a longer latent period (125 min) than other related phages; however, this did not affect its high phage titter (>1010 PFU/mL). The final assembled genome of P7_Pc is 147,299 bp in length with a G+C content of 50.34%. Of the 298 predicted open reading frames (ORFs) of the genome of P7_Pc, putative functions were assigned to 53 ORFs. Seven tRNA-coding genes were predicted in the genome, while the genome lacked any major genes coding for lysogeny-related products, confirming its virulent nature. The P7_Pc genome shares 96.12% and 95.74% average nucleotide identities with Cronobacter phages CR8 and PBES02, respectively. Phylogenetic and phylogenomic analyses of the genome revealed that P7_Pc clusters well within the clade with the members representing the genus Certrevirus. Currently, there are only 4 characterized Pectobacterium phages (P. atrosepticum phages phiTE and CB7 and Pectobacterium phages DU_PP_I and DU_PP_IV) that are classified under the genus, making the phage P7_Pc the first reported member of the genus isolated using the host bacterium P. carotovorum. The results of this study provide a detailed characterization of the phage P7_Pc, enabling its careful classification into the genus Certrevirus. The knowledge gathered on the phage based on the shared biology of the genus will further aid in the future selection of phage P7_Pc as a biocontrol agent. IMPORTANCE Bacterial soft rot disease, caused by Pectobacterium spp., can lead to significant losses in carrot yields. As current control measures involving the use of chemicals or antibiotics are not recommended in many countries, bacteriophage-mediated biocontrol strategies are being explored for the successful control of these phytopathogens. The successful implementation of such biocontrol strategies relies heavily upon the proper understanding of the growth characteristics and genomic properties of the phage. Further, the selection of taxonomically different phages for the formulation of phage cocktails in biocontrol applications is critical to combat potential bacterial resistance development. This study was conducted to carefully characterize and resolve the phylogenetic placement of the P. carotovorum phage vB_PcaM_P7_Pc by using its biological and genomic properties. Phage P7_Pc has a myovirus morphotype with an exclusively lytic life cycle, and the absence of genes related to lysogeny, toxin production, and antibiotic resistance in its genome confirmed its suitability to be used in environmental applications. Furthermore, P7_Pc is classified under the genus Certrevirus, making it the first reported phage of the genus of the host species, P. carotovorum.
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Affiliation(s)
- Kishani N. Naligama
- Department of Microbiology, Faculty of Science, University of Kelaniya, Kelaniya, Sri Lanka
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19
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Srikant S, Guegler CK, Laub MT. The evolution of a counter-defense mechanism in a virus constrains its host range. eLife 2022; 11:79549. [PMID: 35924892 PMCID: PMC9391042 DOI: 10.7554/elife.79549] [Citation(s) in RCA: 22] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2022] [Accepted: 08/03/2022] [Indexed: 11/13/2022] Open
Abstract
Bacteria use diverse immunity mechanisms to defend themselves against their viral predators, bacteriophages. In turn, phages can acquire counter-defense systems, but it remains unclear how such mechanisms arise and what factors constrain viral evolution. Here, we experimentally evolved T4 phage to overcome a phage-defensive toxin-antitoxin system, toxIN, in E. coli. Through recombination, T4 rapidly acquires segmental amplifications of a previously uncharacterized gene, now named tifA, encoding an inhibitor of the toxin, ToxN. These amplifications subsequently drive large deletions elsewhere in T4's genome to maintain a genome size compatible with capsid packaging. The deleted regions include accessory genes that help T4 overcome defense systems in alternative hosts. Thus, our results reveal a trade-off in viral evolution; the emergence of one counter-defense mechanism can lead to loss of other such mechanisms, thereby constraining host range. We propose that the accessory genomes of viruses reflect the integrated evolutionary history of the hosts they infected.
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Affiliation(s)
- Sriram Srikant
- Department of Biology, Massachusetts Institute of Technology, Cambridge, United States
| | - Chantal K Guegler
- Department of Biology, Massachusetts Institute of Technology, Cambridge, United States
| | - Michael T Laub
- Department of Biology, Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, United States
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20
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Qiu J, Zhai Y, Wei M, Zheng C, Jiao X. Toxin–antitoxin systems: Classification, biological roles, and applications. Microbiol Res 2022; 264:127159. [DOI: 10.1016/j.micres.2022.127159] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2022] [Revised: 08/02/2022] [Accepted: 08/03/2022] [Indexed: 11/28/2022]
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21
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Paillet T, Lossouarn J, Figueroa C, Midoux C, Rué O, Petit MA, Dugat-Bony E. Virulent Phages Isolated from a Smear-Ripened Cheese Are Also Detected in Reservoirs of the Cheese Factory. Viruses 2022; 14:v14081620. [PMID: 35893685 PMCID: PMC9331655 DOI: 10.3390/v14081620] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2022] [Revised: 07/20/2022] [Accepted: 07/22/2022] [Indexed: 12/10/2022] Open
Abstract
Smear-ripened cheeses host complex microbial communities that play a crucial role in the ripening process. Although bacteriophages have been frequently isolated from dairy products, their diversity and ecological role in such this type of cheese remain underexplored. In order to fill this gap, the main objective of this study was to isolate and characterize bacteriophages from the rind of a smear-ripened cheese. Thus, viral particles extracted from the cheese rind were tested through a spot assay against a collection of bacteria isolated from the same cheese and identified by sequencing the full-length small subunit ribosomal RNA gene. In total, five virulent bacteriophages infecting Brevibacterium aurantiacum, Glutamicibacter arilaitensis, Leuconostoc falkenbergense and Psychrobacter aquimaris species were obtained. All exhibit a narrow host range, being only able to infect a few cheese-rind isolates within the same species. The complete genome of each phage was sequenced using both Nanopore and Illumina technologies, assembled and annotated. A sequence comparison with known phages revealed that four of them may represent at least new genera. The distribution of the five virulent phages into the dairy-plant environment was also investigated by PCR, and three potential reservoirs were identified. This work provides new knowledge on the cheese rind viral community and an overview of the distribution of phages within a cheese factory.
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Affiliation(s)
- Thomas Paillet
- Université Paris-Saclay, INRAE, AgroParisTech, UMR SayFood, 91120 Palaiseau, France; (T.P.); (C.F.)
| | - Julien Lossouarn
- Université Paris-Saclay, INRAE, AgroParisTech, Micalis Institute, 78352 Jouy-en-Josas, France; (J.L.); (M.-A.P.)
| | - Clarisse Figueroa
- Université Paris-Saclay, INRAE, AgroParisTech, UMR SayFood, 91120 Palaiseau, France; (T.P.); (C.F.)
| | - Cédric Midoux
- Université Paris-Saclay, INRAE, MaIAGE, 78350 Jouy-en-Josas, France; (C.M.); (O.R.)
- Université Paris-Saclay, INRAE, BioinfOmics, MIGALE Bioinformatics Facility, 78350 Jouy-en-Josas, France
- Université Paris-Saclay, INRAE, PROSE, 92761 Antony, France
| | - Olivier Rué
- Université Paris-Saclay, INRAE, MaIAGE, 78350 Jouy-en-Josas, France; (C.M.); (O.R.)
- Université Paris-Saclay, INRAE, BioinfOmics, MIGALE Bioinformatics Facility, 78350 Jouy-en-Josas, France
| | - Marie-Agnès Petit
- Université Paris-Saclay, INRAE, AgroParisTech, Micalis Institute, 78352 Jouy-en-Josas, France; (J.L.); (M.-A.P.)
| | - Eric Dugat-Bony
- Université Paris-Saclay, INRAE, AgroParisTech, UMR SayFood, 91120 Palaiseau, France; (T.P.); (C.F.)
- Correspondence:
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22
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Abstract
Toxin-antitoxin (TA) systems are ubiquitous genetic elements in bacteria that consist of a growth-inhibiting toxin and its cognate antitoxin. These systems are prevalent in bacterial chromosomes, plasmids, and phage genomes, but individual systems are not highly conserved, even among closely related strains. The biological functions of TA systems have been controversial and enigmatic, although a handful of these systems have been shown to defend bacteria against their viral predators, bacteriophages. Additionally, their patterns of conservation-ubiquitous, but rapidly acquired and lost from genomes-as well as the co-occurrence of some TA systems with known phage defense elements are suggestive of a broader role in mediating phage defense. Here, we review the existing evidence for phage defense mediated by TA systems, highlighting how toxins are activated by phage infection and how toxins disrupt phage replication. We also discuss phage-encoded systems that counteract TA systems, underscoring the ongoing coevolutionary battle between bacteria and phage. We anticipate that TA systems will continue to emerge as central players in the innate immunity of bacteria against phage. Expected final online publication date for the Annual Review of Microbiology, Volume 76 is September 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
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Affiliation(s)
- Michele LeRoux
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA;
| | - Michael T Laub
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA; .,Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
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23
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Manikandan P, Sandhya S, Nadig K, Paul S, Srinivasan N, Rothweiler U, Singh M. Identification, functional characterization, assembly and structure of ToxIN type III toxin-antitoxin complex from E. coli. Nucleic Acids Res 2022; 50:1687-1700. [PMID: 35018473 PMCID: PMC8860590 DOI: 10.1093/nar/gkab1264] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2021] [Revised: 11/26/2021] [Accepted: 12/09/2021] [Indexed: 11/21/2022] Open
Abstract
Toxin–antitoxin (TA) systems are proposed to play crucial roles in bacterial growth under stress conditions such as phage infection. The type III TA systems consist of a protein toxin whose activity is inhibited by a noncoding RNA antitoxin. The toxin is an endoribonuclease, while the antitoxin consists of multiple repeats of RNA. The toxin assembles with the individual antitoxin repeats into a cyclic complex in which the antitoxin forms a pseudoknot structure. While structure and functions of some type III TA systems are characterized, the complex assembly process is not well understood. Using bioinformatics analysis, we have identified type III TA systems belonging to the ToxIN family across different Escherichia coli strains and found them to be clustered into at least five distinct clusters. Furthermore, we report a 2.097 Å resolution crystal structure of the first E. coli ToxIN complex that revealed the overall assembly of the protein-RNA complex. Isothermal titration calorimetry experiments showed that toxin forms a high-affinity complex with antitoxin RNA resulting from two independent (5′ and 3′ sides of RNA) RNA binding sites on the protein. These results further our understanding of the assembly of type III TA complexes in bacteria.
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Affiliation(s)
| | - Sankaran Sandhya
- Molecular Biophysics Unit, Indian Institute of Science, Bengaluru 560012, India
| | - Kavyashree Nadig
- Molecular Biophysics Unit, Indian Institute of Science, Bengaluru 560012, India
| | - Souradip Paul
- Molecular Biophysics Unit, Indian Institute of Science, Bengaluru 560012, India
| | | | - Ulli Rothweiler
- The Norwegian Structural Biology Centre, Department of Chemistry, The Arctic University of Norway, N-9037 Tromsø, Norway
| | - Mahavir Singh
- Molecular Biophysics Unit, Indian Institute of Science, Bengaluru 560012, India
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24
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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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25
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Egido JE, Costa AR, Aparicio-Maldonado C, Haas PJ, Brouns SJJ. Mechanisms and clinical importance of bacteriophage resistance. FEMS Microbiol Rev 2021; 46:6374866. [PMID: 34558600 PMCID: PMC8829019 DOI: 10.1093/femsre/fuab048] [Citation(s) in RCA: 84] [Impact Index Per Article: 28.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2021] [Accepted: 09/15/2021] [Indexed: 12/24/2022] Open
Abstract
We are in the midst of a golden age of uncovering defense systems against bacteriophages. Apart from the fundamental interest in these defense systems, and revolutionary applications that have been derived from them (e.g. CRISPR-Cas9 and restriction endonucleases), it is unknown how defense systems contribute to resistance formation against bacteriophages in clinical settings. Bacteriophages are now being reconsidered as therapeutic agents against bacterial infections due the emergence of multidrug resistance. However, bacteriophage resistance through defense systems and other means could hinder the development of successful phage-based therapies. Here, we review the current state of the field of bacteriophage defense, highlight the relevance of bacteriophage defense for potential clinical use of bacteriophages as therapeutic agents and suggest new directions of research.
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Affiliation(s)
- Julia E Egido
- Medical Microbiology, University Medical Center Utrecht, Utrecht University, Heidelberglaan 100, 3584 CX Utrecht, Netherlands
| | - Ana Rita Costa
- Department of Bionanoscience, Delft University of Technology, van der Maasweg 9, 2629 HZ Delft, Netherlands.,Kavli Institute of Nanoscience, Delft, Netherlands.,Fagenbank, Delft, Netherlands
| | - Cristian Aparicio-Maldonado
- Department of Bionanoscience, Delft University of Technology, van der Maasweg 9, 2629 HZ Delft, Netherlands.,Kavli Institute of Nanoscience, Delft, Netherlands
| | - Pieter-Jan Haas
- Medical Microbiology, University Medical Center Utrecht, Utrecht University, Heidelberglaan 100, 3584 CX Utrecht, Netherlands
| | - Stan J J Brouns
- Department of Bionanoscience, Delft University of Technology, van der Maasweg 9, 2629 HZ Delft, Netherlands.,Kavli Institute of Nanoscience, Delft, Netherlands.,Fagenbank, Delft, Netherlands
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26
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Miroshnikov KA, Evseev PV, Lukianova AA, Ignatov AN. Tailed Lytic Bacteriophages of Soft Rot Pectobacteriaceae. Microorganisms 2021; 9:1819. [PMID: 34576713 PMCID: PMC8472413 DOI: 10.3390/microorganisms9091819] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2021] [Revised: 08/23/2021] [Accepted: 08/24/2021] [Indexed: 02/07/2023] Open
Abstract
The study of the ecological and evolutionary traits of Soft Rot Pectobacteriaceae (SRP) comprising genera Pectobacterium and Dickeya often involves bacterial viruses (bacteriophages). Bacteriophages are considered to be a prospective tool for the ecologically safe and highly specific protection of plants and harvests from bacterial diseases. Information concerning bacteriophages has been growing rapidly in recent years, and this has included new genomics-based principles of taxonomic distribution. In this review, we summarise the data on phages infecting Pectobacterium and Dickeya that are available in publications and genomic databases. The analysis highlights not only major genomic properties that assign phages to taxonomic families and genera, but also the features that make them potentially suitable for phage control applications. Specifically, there is a discussion of the molecular mechanisms of receptor recognition by the phages and problems concerning the evolution of phage-resistant mutants.
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Affiliation(s)
- Konstantin A Miroshnikov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Miklukho-Maklaya Str., 16/10, 117997 Moscow, Russia
- Timiryazev Agricultural Academy, Russian State Agrarian University, Timiryazevskaya Str., 49, 127434 Moscow, Russia
| | - Peter V Evseev
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Miklukho-Maklaya Str., 16/10, 117997 Moscow, Russia
| | - Anna A Lukianova
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Miklukho-Maklaya Str., 16/10, 117997 Moscow, Russia
- Timiryazev Agricultural Academy, Russian State Agrarian University, Timiryazevskaya Str., 49, 127434 Moscow, Russia
- Department of Biology, Lomonosov Moscow State University, Leninskie Gory, 1, bldg. 12, 119234 Moscow, Russia
| | - Alexander N Ignatov
- Timiryazev Agricultural Academy, Russian State Agrarian University, Timiryazevskaya Str., 49, 127434 Moscow, Russia
- Agrobiotechnology Department, Agrarian and Technological Institute, RUDN University, Miklukho-Maklaya Str., 6, 117198 Moscow, Russia
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27
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Abstract
Control of pathogenic bacteria by deliberate application of predatory phages has potential as a powerful therapy against antibiotic-resistant bacteria. The key advantages of phage biocontrol over antibacterial chemotherapy are: (1) an ability to self-propagate inside host bacteria, (2) targeted predation of specific species or strains of bacteria, (3) adaptive molecular machinery to overcome resistance in target bacteria. However, realizing the potential of phage biocontrol is dependent on harnessing or adapting these responses, as many phage species switch between lytic infection cycles (resulting in lysis) and lysogenic infection cycles (resulting in genomic integration) that increase the likelihood of survival of the phage in response to external stress or host depletion. Similarly, host range will need to be optimized to make phage therapy medically viable whilst avoiding the potential for deleteriously disturbing the commensal microbiota. Phage training is a new approach to produce efficient phages by capitalizing on the evolved response of wild-type phages to bacterial resistance. Here we will review recent studies reporting successful trials of training different strains of phages to switch into lytic replication mode, overcome bacterial resistance, and increase their host range. This review will also highlight the current knowledge of phage training and future implications in phage applications and phage therapy and summarize the recent pipeline of the magistral preparation to produce a customized phage for clinical trials and medical applications.
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28
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Abd-Allah IM, El-Housseiny GS, Yahia IS, Aboshanab KM, Hassouna NA. Rekindling of a Masterful Precedent; Bacteriophage: Reappraisal and Future Pursuits. Front Cell Infect Microbiol 2021; 11:635597. [PMID: 34136415 PMCID: PMC8201069 DOI: 10.3389/fcimb.2021.635597] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2021] [Accepted: 05/13/2021] [Indexed: 12/30/2022] Open
Abstract
Antibiotic resistance is exuberantly becoming a deleterious health problem world-wide. Seeking innovative approaches is necessary in order to circumvent such a hazard. An unconventional fill-in to antibiotics is bacteriophage. Bacteriophages are viruses capable of pervading bacterial cells and disrupting their natural activity, ultimately resulting in their defeat. In this article, we will run-through the historical record of bacteriophage and its correlation with bacteria. We will also delineate the potential of bacteriophage as a therapeutic antibacterial agent, its supremacy over antibiotics in multiple aspects and the challenges that could arise on the way to its utilization in reality. Pharmacodynamics, pharmacokinetics and genetic engineering of bacteriophages and its proteins will be briefly discussed as well. In addition, we will highlight some of the in-use applications of bacteriophages, and set an outlook for their future ones. We will also overview some of the miscellaneous abilities of these tiny viruses in several fields other than the clinical one. This is an attempt to encourage tackling a long-forgotten hive. Perhaps, one day, the smallest of the creatures would be of the greatest help.
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Affiliation(s)
- Israa M. Abd-Allah
- Department of Microbiology and Immunology, Faculty of Pharmacy, Ain Shams University, Cairo, Egypt
| | - Ghadir S. El-Housseiny
- Department of Microbiology and Immunology, Faculty of Pharmacy, Ain Shams University, Cairo, Egypt
| | - Ibrahim S. Yahia
- Research Center for Advanced Materials Science (RCAMS), Advanced Functional Materials & Optoelectronic Laboratory (AFMOL), Department of Physics, Faculty of Science, King Khalid University, Abha, Saudi Arabia
- Nanoscience Laboratory for Environmental and Bio-Medical Applications (NLEBA), Semiconductor Lab., Metallurgical Lab, Physics Department, Faculty of Education, Ain Shams University, Cairo, Egypt
| | - Khaled M. Aboshanab
- Department of Microbiology and Immunology, Faculty of Pharmacy, Ain Shams University, Cairo, Egypt
| | - Nadia A. Hassouna
- Department of Microbiology and Immunology, Faculty of Pharmacy, Ain Shams University, Cairo, Egypt
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29
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Huang Z, Zhang Z, Tong J, Malakar PK, Chen L, Liu H, Pan Y, Zhao Y. Phages and their lysins: Toolkits in the battle against foodborne pathogens in the postantibiotic era. Compr Rev Food Sci Food Saf 2021; 20:3319-3343. [PMID: 33938116 DOI: 10.1111/1541-4337.12757] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2020] [Revised: 03/22/2021] [Accepted: 03/25/2021] [Indexed: 12/13/2022]
Abstract
Worldwide, foods waste caused by putrefactive organisms and diseases caused by foodborne pathogens persist as public health problems even with a plethora of modern antimicrobials. Our over reliance on antimicrobials use in agriculture, medicine, and other fields will lead to a postantibiotic era where bacterial genotypic resistance, phenotypic adaptation, and other bacterial evolutionary strategies cause antimicrobial resistance (AMR). This AMR is evidenced by the emergence of multiple drug-resistant (MDR) bacteria and pan-resistant (PDR) bacteria, which produces cross-contamination in multiple fields and poses a more serious threat to food safety. A "red queen premise" surmises that the coevolution of phages and bacteria results in an evolutionary arms race that compels phages to adapt and survive bacterial antiphage strategies. Phages and their lysins are therefore useful toolkits in the design of novel antimicrobials in food protection and foodborne pathogens control, and the modality of using phages as a targeted vector against foodborne pathogens is gaining momentum based on many encouraging research outcomes. In this review, we discuss the rationale of using phages and their lysins as weapons against spoilage organisms and foodborne pathogens, and outline the targeted conquest or dodge mechanism of phages and the development of novel phage prospects. We also highlight the implementation of phages and their lysins to control foodborne pathogens in a farm-table-hospital domain in the postantibiotic era.
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Affiliation(s)
- Zhenhua Huang
- College of Food Science and Technology, Shanghai Ocean University, Shanghai, China
| | - Zhaohuan Zhang
- College of Food Science and Technology, Shanghai Ocean University, Shanghai, China.,College of Fisheries and Life Science, Shanghai Ocean University, Shanghai, 201306, China
| | - Jinrong Tong
- College of Food Science and Technology, Shanghai Ocean University, Shanghai, China
| | - Pradeep K Malakar
- College of Food Science and Technology, Shanghai Ocean University, Shanghai, China
| | - Liangbiao Chen
- College of Fisheries and Life Science, Shanghai Ocean University, Shanghai, 201306, China
| | - Haiquan Liu
- College of Food Science and Technology, Shanghai Ocean University, Shanghai, China.,Laboratory of Quality & Safety Risk Assessment for Aquatic Products on Storage and Preservation (Shanghai), Ministry of Agriculture and Rural Affairs, Shanghai, China.,Shanghai Engineering Research Center of Aquatic-Product Processing & Preservation, Shanghai, China
| | - Yingjie Pan
- College of Food Science and Technology, Shanghai Ocean University, Shanghai, China.,Laboratory of Quality & Safety Risk Assessment for Aquatic Products on Storage and Preservation (Shanghai), Ministry of Agriculture and Rural Affairs, Shanghai, China.,Shanghai Engineering Research Center of Aquatic-Product Processing & Preservation, Shanghai, China
| | - Yong Zhao
- College of Food Science and Technology, Shanghai Ocean University, Shanghai, China.,Laboratory of Quality & Safety Risk Assessment for Aquatic Products on Storage and Preservation (Shanghai), Ministry of Agriculture and Rural Affairs, Shanghai, China.,Shanghai Engineering Research Center of Aquatic-Product Processing & Preservation, Shanghai, China
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30
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Łobocka M, Dąbrowska K, Górski A. Engineered Bacteriophage Therapeutics: Rationale, Challenges and Future. BioDrugs 2021; 35:255-280. [PMID: 33881767 PMCID: PMC8084836 DOI: 10.1007/s40259-021-00480-z] [Citation(s) in RCA: 62] [Impact Index Per Article: 20.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/29/2021] [Indexed: 12/20/2022]
Abstract
The current problems with increasing bacterial resistance to antibacterial therapies, resulting in a growing frequency of incurable bacterial infections, necessitates the acceleration of studies on antibacterials of a new generation that could offer an alternative to antibiotics or support their action. Bacteriophages (phages) can kill antibiotic-sensitive as well as antibiotic-resistant bacteria, and thus are a major subject of such studies. Their efficacy in curing bacterial infections has been demonstrated in in vivo experiments and in the clinic. Unlike antibiotics, phages have a narrow range of specificity, which makes them safe for commensal microbiota. However, targeting even only the most clinically relevant strains of pathogenic bacteria requires large collections of well characterized phages, whose specificity would cover all such strains. The environment is a rich source of diverse phages, but due to their complex relationships with bacteria and safety concerns, only some naturally occurring phages can be considered for therapeutic applications. Still, their number and diversity make a detailed characterization of all potentially promising phages virtually impossible. Moreover, no single phage combines all the features required of an ideal therapeutic agent. Additionally, the rapid acquisition of phage resistance by bacteria may make phages already approved for therapy ineffective and turn the search for environmental phages of better efficacy and new specificity into an endless race. An alternative strategy for acquiring phages with desired properties in a short time with minimal cost regarding their acquisition, characterization, and approval for therapy could be based on targeted genome modifications of phage isolates with known properties. The first example demonstrating the potential of this strategy in curing bacterial diseases resistant to traditional therapy is the recent successful treatment of a progressing disseminated Mycobacterium abscessus infection in a teenage patient with the use of an engineered phage. In this review, we briefly present current methods of phage genetic engineering, highlighting their advantages and disadvantages, and provide examples of genetically engineered phages with a modified host range, improved safety or antibacterial activity, and proven therapeutic efficacy. We also summarize novel uses of engineered phages not only for killing pathogenic bacteria, but also for in situ modification of human microbiota to attenuate symptoms of certain bacterial diseases and metabolic, immune, or mental disorders.
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Affiliation(s)
- Małgorzata Łobocka
- Institute of Biochemistry and Biophysics of the Polish Academy of Sciences, Warsaw, Poland
| | - Krystyna Dąbrowska
- Institute of Immunology and Experimental Therapy of the Polish Academy of Sciences, Wrocław, Poland
| | - Andrzej Górski
- Institute of Immunology and Experimental Therapy of the Polish Academy of Sciences, Wrocław, Poland
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31
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Pinilla-Redondo R, Shehreen S, Marino ND, Fagerlund RD, Brown CM, Sørensen SJ, Fineran PC, Bondy-Denomy J. Discovery of multiple anti-CRISPRs highlights anti-defense gene clustering in mobile genetic elements. Nat Commun 2020; 11:5652. [PMID: 33159058 PMCID: PMC7648647 DOI: 10.1038/s41467-020-19415-3] [Citation(s) in RCA: 68] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2020] [Accepted: 10/06/2020] [Indexed: 12/14/2022] Open
Abstract
Many prokaryotes employ CRISPR-Cas systems to combat invading mobile genetic elements (MGEs). In response, some MGEs have developed strategies to bypass immunity, including anti-CRISPR (Acr) proteins; yet the diversity, distribution and spectrum of activity of this immune evasion strategy remain largely unknown. Here, we report the discovery of new Acrs by assaying candidate genes adjacent to a conserved Acr-associated (Aca) gene, aca5, against a panel of six type I systems: I-F (Pseudomonas, Pectobacterium, and Serratia), I-E (Pseudomonas and Serratia), and I-C (Pseudomonas). We uncover 11 type I-F and/or I-E anti-CRISPR genes encoded on chromosomal and extrachromosomal MGEs within Enterobacteriaceae and Pseudomonas, and an additional Aca (aca9). The acr genes not only associate with other acr genes, but also with genes encoding inhibitors of distinct bacterial defense systems. Thus, our findings highlight the potential exploitation of acr loci neighborhoods for the identification of previously undescribed anti-defense systems.
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Affiliation(s)
- Rafael Pinilla-Redondo
- Section of Microbiology, University of Copenhagen, Copenhagen, Denmark
- Department of Microbiology and Immunology, University of California, San Francisco, CA, USA
- University College Copenhagen, Copenhagen, Denmark
| | - Saadlee Shehreen
- Department of Biochemistry, University of Otago, Dunedin, New Zealand
| | - Nicole D Marino
- Department of Microbiology and Immunology, University of California, San Francisco, CA, USA
| | - Robert D Fagerlund
- Department of Microbiology and Immunology, University of Otago, Dunedin, New Zealand
- Genetics Otago, University of Otago, Dunedin, New Zealand
| | - Chris M Brown
- Department of Biochemistry, University of Otago, Dunedin, New Zealand
- Genetics Otago, University of Otago, Dunedin, New Zealand
| | - Søren J Sørensen
- Section of Microbiology, University of Copenhagen, Copenhagen, Denmark
| | - Peter C Fineran
- Department of Microbiology and Immunology, University of Otago, Dunedin, New Zealand.
- Genetics Otago, University of Otago, Dunedin, New Zealand.
- Bio-protection Research Centre, University of Otago, Dunedin, New Zealand.
| | - Joseph Bondy-Denomy
- Department of Microbiology and Immunology, University of California, San Francisco, CA, USA.
- Quantitative Biosciences Institute, UCSF, San Francisco, CA, USA.
- Innovative Genomics Institute, Berkeley, CA, USA.
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32
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Guerin E, Hill C. Shining Light on Human Gut Bacteriophages. Front Cell Infect Microbiol 2020; 10:481. [PMID: 33014897 PMCID: PMC7511551 DOI: 10.3389/fcimb.2020.00481] [Citation(s) in RCA: 46] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2020] [Accepted: 08/04/2020] [Indexed: 12/15/2022] Open
Abstract
The human gut is a complex environment that contains a multitude of microorganisms that are collectively termed the microbiome. Multiple factors have a role to play in driving the composition of human gut bacterial communities either toward homeostasis or the instability that is associated with many disease states. One of the most important forces are likely to be bacteriophages, bacteria-infecting viruses that constitute by far the largest portion of the human gut virome. Despite this, bacteriophages (phages) are the one of the least studied residents of the gut. This is largely due to the challenges associated with studying these difficult to culture entities. Modern high throughput sequencing technologies have played an important role in improving our understanding of the human gut phageome but much of the generated sequencing data remains uncharacterised. Overcoming this requires database-independent bioinformatic pipelines and even those phages that are successfully characterized only provide limited insight into their associated biological properties, and thus most viral sequences have been characterized as “viral dark matter.” Fundamental to understanding the role of phages in shaping the human gut microbiome, and in turn perhaps influencing human health, is how they interact with their bacterial hosts. An essential aspect is the isolation of novel phage-bacteria host pairs by direct isolation through various screening methods, which can transform in silico phages into a biological reality. However, this is also beset with multiple challenges including culturing difficulties and the use of traditional methods, such as plaquing, which may bias which phage-host pairs that can be successfully isolated. Phage-bacteria interactions may be influenced by many aspects of complex human gut biology which can be difficult to reproduce under laboratory conditions. Here we discuss some of the main findings associated with the human gut phageome to date including composition, our understanding of phage-host interactions, particularly the observed persistence of virulent phages and their hosts, as well as factors that may influence these highly intricate relationships. We also discuss current methodologies and bottlenecks hindering progression in this field and identify potential steps that may be useful in overcoming these hurdles.
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Affiliation(s)
- Emma Guerin
- APC Microbiome Ireland, University College Cork, Cork, Ireland.,School of Microbiology, University College Cork, Cork, Ireland
| | - Colin Hill
- APC Microbiome Ireland, University College Cork, Cork, Ireland.,School of Microbiology, University College Cork, Cork, Ireland
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33
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Federici S, Nobs SP, Elinav E. Phages and their potential to modulate the microbiome and immunity. Cell Mol Immunol 2020; 18:889-904. [PMID: 32901128 DOI: 10.1038/s41423-020-00532-4] [Citation(s) in RCA: 78] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Accepted: 08/06/2020] [Indexed: 02/07/2023] Open
Abstract
Bacteriophages (hence termed phages) are viruses that target bacteria and have long been considered as potential future treatments against antibiotic-resistant bacterial infection. However, the molecular nature of phage interactions with bacteria and the human host has remained elusive for decades, limiting their therapeutic application. While many phages and their functional repertoires remain unknown, the advent of next-generation sequencing has increasingly enabled researchers to decode new lytic and lysogenic mechanisms by which they attack and destroy bacteria. Furthermore, the last decade has witnessed a renewed interest in the utilization of phages as therapeutic vectors and as a means of targeting pathogenic or commensal bacteria or inducing immunomodulation. Importantly, the narrow host range, immense antibacterial repertoire, and ease of manipulating phages may potentially allow for their use as targeted modulators of pathogenic, commensal and pathobiont members of the microbiome, thereby impacting mammalian physiology and immunity along mucosal surfaces in health and in microbiome-associated diseases. In this review, we aim to highlight recent advances in phage biology and how a mechanistic understanding of phage-bacteria-host interactions may facilitate the development of novel phage-based therapeutics. We provide an overview of the challenges of the therapeutic use of phages and how these could be addressed for future use of phages as specific modulators of the human microbiome in a variety of infectious and noncommunicable human diseases.
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Affiliation(s)
- Sara Federici
- Immunology Department, Weizmann Institute of Science, Rehovot, 7610001, Israel
| | - Samuel P Nobs
- Immunology Department, Weizmann Institute of Science, Rehovot, 7610001, Israel
| | - Eran Elinav
- Immunology Department, Weizmann Institute of Science, Rehovot, 7610001, Israel. .,Cancer-Microbiome Division Deutsches Krebsforschungszentrum (DKFZ), Neuenheimer Feld 280, 69120, Heidelberg, Germany.
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34
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Buttimer C, Lynch C, Hendrix H, Neve H, Noben JP, Lavigne R, Coffey A. Isolation and Characterization of Pectobacterium Phage vB_PatM_CB7: New Insights into the Genus Certrevirus. Antibiotics (Basel) 2020; 9:E352. [PMID: 32575906 PMCID: PMC7344957 DOI: 10.3390/antibiotics9060352] [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: 05/29/2020] [Revised: 06/18/2020] [Accepted: 06/19/2020] [Indexed: 12/20/2022] Open
Abstract
To date, Certrevirus is one of two genera of bacteriophage (phage), with phages infecting Pectobacterium atrosepticum, an economically important phytopathogen that causes potato blackleg and soft rot disease. This study provides a detailed description of Pectobacterium phage CB7 (vB_PatM_CB7), which specifically infects P. atrosepticum. Host range, morphology, latent period, burst size and stability at different conditions of temperature and pH were examined. Analysis of its genome (142.8 kbp) shows that the phage forms a new species of Certrevirus, sharing sequence similarity with other members, highlighting conservation within the genus. Conserved elements include a putative early promoter like that of the Escherichia coli sigma70 promoter, which was found to be shared with other genus members. A number of dissimilarities were observed, relating to DNA methylation and nucleotide metabolism. Some members do not have homologues of a cytosine methylase and anaerobic nucleotide reductase subunits NrdD and NrdG, respectively. Furthermore, the genome of CB7 contains one of the largest numbers of homing endonucleases described in a single phage genome in the literature to date, with a total of 23 belonging to the HNH and LAGLIDADG families. Analysis by RT-PCR of the HNH homing endonuclease residing within introns of genes for the large terminase, DNA polymerase, ribonucleotide reductase subunits NrdA and NrdB show that they are splicing competent. Electrospray ionization-tandem mass spectrometry (ESI-MS/MS) was also performed on the virion of CB7, allowing the identification of 26 structural proteins-20 of which were found to be shared with the type phages of the genera of Vequintavirus and Seunavirus. The results of this study provide greater insights into the phages of the Certrevirus genus as well as the subfamily Vequintavirinae.
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Affiliation(s)
- Colin Buttimer
- Department of Biological Sciences, Cork Institute of Technology, T12 P928 Cork, Ireland; (C.B.); (C.L.)
- APC Microbiome Institute, University College, T12 YT20 Cork, Ireland
| | - Caoimhe Lynch
- Department of Biological Sciences, Cork Institute of Technology, T12 P928 Cork, Ireland; (C.B.); (C.L.)
| | - Hanne Hendrix
- Laboratory of Gene Technology, KU Leuven, 3001 Leuven, Belgium; (H.H.); (R.L.)
| | - Horst Neve
- Department of Microbiology and Biotechnology, Max Rubner-Institut, 24103 Kiel, Germany;
| | - Jean-Paul Noben
- Biomedical Research Institute and Transnational University Limburg, Hasselt University, 3590 Hasselt, Belgium;
| | - Rob Lavigne
- Laboratory of Gene Technology, KU Leuven, 3001 Leuven, Belgium; (H.H.); (R.L.)
| | - Aidan Coffey
- Department of Biological Sciences, Cork Institute of Technology, T12 P928 Cork, Ireland; (C.B.); (C.L.)
- APC Microbiome Institute, University College, T12 YT20 Cork, Ireland
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35
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Abstract
Facing frequent phage challenges, bacteria have evolved numerous mechanisms to resist phage infection. A commonly used phage resistance strategy is abortive infection (Abi), in which the infected cell commits suicide before the phage can complete its replication cycle. Abi prevents the phage epidemic from spreading to nearby cells, thus protecting the bacterial colony. The Abi strategy is manifested by a plethora of mechanistically diverse defense systems that are abundant in bacterial genomes. In turn, phages have developed equally diverse mechanisms to overcome bacterial Abi. This review summarizes the current knowledge on bacterial defense via cell suicide. It describes the principles of Abi, details how these principles are implemented in a variety of natural defense systems, and discusses phage counter-defense mechanisms.
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Affiliation(s)
- Anna Lopatina
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel;
| | - Nitzan Tal
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel;
| | - Rotem Sorek
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel;
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36
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The arms race between bacteria and their phage foes. Nature 2020; 577:327-336. [PMID: 31942051 DOI: 10.1038/s41586-019-1894-8] [Citation(s) in RCA: 409] [Impact Index Per Article: 102.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2019] [Accepted: 11/13/2019] [Indexed: 12/26/2022]
Abstract
Bacteria are under immense evolutionary pressure from their viral invaders-bacteriophages. Bacteria have evolved numerous immune mechanisms, both innate and adaptive, to cope with this pressure. The discovery and exploitation of CRISPR-Cas systems have stimulated a resurgence in the identification and characterization of anti-phage mechanisms. Bacteriophages use an extensive battery of counter-defence strategies to co-exist in the presence of these diverse phage defence mechanisms. Understanding the dynamics of the interactions between these microorganisms has implications for phage-based therapies, microbial ecology and evolution, and the development of new biotechnological tools. Here we review the spectrum of anti-phage systems and highlight their evasion by bacteriophages.
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Watson BNJ, Vercoe RB, Salmond GPC, Westra ER, Staals RHJ, Fineran PC. Type I-F CRISPR-Cas resistance against virulent phages results in abortive infection and provides population-level immunity. Nat Commun 2019; 10:5526. [PMID: 31797922 PMCID: PMC6892833 DOI: 10.1038/s41467-019-13445-2] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2019] [Accepted: 10/30/2019] [Indexed: 12/18/2022] Open
Abstract
Type I CRISPR-Cas systems are abundant and widespread adaptive immune systems in bacteria and can greatly enhance bacterial survival in the face of phage infection. Upon phage infection, some CRISPR-Cas immune responses result in bacterial dormancy or slowed growth, which suggests the outcomes for infected cells may vary between systems. Here we demonstrate that type I CRISPR immunity of Pectobacterium atrosepticum leads to suppression of two unrelated virulent phages, ɸTE and ɸM1. Immunity results in an abortive infection response, where infected cells do not survive, but viral propagation is severely decreased, resulting in population protection due to the reduced phage epidemic. Our findings challenge the view of CRISPR-Cas as a system that protects the individual cell and supports growing evidence of abortive infection by some types of CRISPR-Cas systems.
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Affiliation(s)
- Bridget N J Watson
- Department of Microbiology and Immunology, University of Otago, Dunedin, 9054, New Zealand
- ESI, Biosciences, University of Exeter, Cornwall Campus, Penryn, TR10 9FE, UK
| | - Reuben B Vercoe
- Department of Microbiology and Immunology, University of Otago, Dunedin, 9054, New Zealand
| | - George P C Salmond
- Department of Biochemistry, University of Cambridge, Cambridge, CB2 1QW, UK
| | - Edze R Westra
- ESI, Biosciences, University of Exeter, Cornwall Campus, Penryn, TR10 9FE, UK
| | - Raymond H J Staals
- Department of Microbiology and Immunology, University of Otago, Dunedin, 9054, New Zealand
- Laboratory of Microbiology, Wageningen University and Research, 6708, WE, Wageningen, The Netherlands
| | - Peter C Fineran
- Department of Microbiology and Immunology, University of Otago, Dunedin, 9054, New Zealand.
- Bio-Protection Research Centre, University of Otago, Dunedin, New Zealand.
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Andrade-Martínez JS, Moreno-Gallego JL, Reyes A. Defining a Core Genome for the Herpesvirales and Exploring their Evolutionary Relationship with the Caudovirales. Sci Rep 2019; 9:11342. [PMID: 31383901 PMCID: PMC6683198 DOI: 10.1038/s41598-019-47742-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2019] [Accepted: 07/19/2019] [Indexed: 12/21/2022] Open
Abstract
The order Herpesvirales encompasses a wide variety of important and broadly distributed human pathogens. During the last decades, similarities in the viral cycle and the structure of some of their proteins with those of the order Caudovirales, the tailed bacterial viruses, have brought speculation regarding the existence of an evolutionary relationship between these clades. To evaluate such hypothesis, we used over 600 Herpesvirales and 2000 Caudovirales complete genomes to search for the presence or absence of clusters of orthologous protein domains and constructed a dendrogram based on their compositional similarities. The results obtained strongly suggest an evolutionary relationship between the two orders. Furthermore, they allowed to propose a core genome for the Herpesvirales, composed of 4 proteins, including the ATPase subunit of the DNA-packaging terminase, the only protein with previously verified conservation. Accordingly, a phylogenetic tree constructed with sequences derived from the clusters associated to these proteins grouped the Herpesvirales strains accordingly to the established families and subfamilies. Overall, this work provides results supporting the hypothesis that the two orders are evolutionarily related and contributes to the understanding of the history of the Herpesvirales.
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Affiliation(s)
- Juan S Andrade-Martínez
- Research Group on Computational Biology and Microbial Ecology, Department of Biological Sciences, Universidad de los Andes, Bogota, Colombia
- Max Planck Tandem Group in Computational Biology, Universidad de los Andes, Bogota, Colombia
| | - J Leonardo Moreno-Gallego
- Research Group on Computational Biology and Microbial Ecology, Department of Biological Sciences, Universidad de los Andes, Bogota, Colombia
- Max Planck Tandem Group in Computational Biology, Universidad de los Andes, Bogota, Colombia
| | - Alejandro Reyes
- Research Group on Computational Biology and Microbial Ecology, Department of Biological Sciences, Universidad de los Andes, Bogota, Colombia.
- Max Planck Tandem Group in Computational Biology, Universidad de los Andes, Bogota, Colombia.
- Centre for Genome Sciences and Systems Biology, Department of Pathology and Immunology, Washington University in Saint Louis, Saint Louis, MO, 63108, USA.
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Hampton HG, Patterson AG, Chang JT, Taylor C, Fineran PC. GalK limits type I-F CRISPR-Cas expression in a CRP-dependent manner. FEMS Microbiol Lett 2019; 366:5521891. [DOI: 10.1093/femsle/fnz137] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2019] [Accepted: 06/19/2019] [Indexed: 12/14/2022] Open
Abstract
ABSTRACTCRISPR-Cas adaptive immune systems protect bacteria from phage predation, and other foreign genetic elements such as plasmids. Significant advances have been made regarding how CRISPR-Cas systems elicit immunity; however, comparatively little is known about their regulation. To study CRISPR-Cas regulation, we describe the construction of suicide lacZ-reporter plasmids with different antibiotic resistance cassettes. Through recombination into the host chromosome, single-copy expression can be achieved, thus preserving natural gene expression and maintaining a reporter expression output that reflects regulation within a normal genomic context. Previous work determined that the galactose metabolism gene galM, decreased the expression of the cas operon in Pectobacterium atrosepticum. We used the new integrative reporters to investigate galK, a gene that is located elsewhere in the genome and is responsible for the conversion of α-D-Galactose to Galactose-1-P during galactose metabolism. Deletion of galK led to elevated cas expression in a CRP-dependent manner but had no effect on CRISPR array expression. These results highlight that the metabolic status of the host cell is linked to the induction of CRISPR-Cas immunity.
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Affiliation(s)
- Hannah G Hampton
- Department of Microbiology and Immunology, University of Otago, PO Box 56, Dunedin 9054, New Zealand
| | - Adrian G Patterson
- Department of Microbiology and Immunology, University of Otago, PO Box 56, Dunedin 9054, New Zealand
| | - James T Chang
- Department of Microbiology and Immunology, University of Otago, PO Box 56, Dunedin 9054, New Zealand
| | - Corinda Taylor
- Department of Microbiology and Immunology, University of Otago, PO Box 56, Dunedin 9054, New Zealand
| | - Peter C Fineran
- Department of Microbiology and Immunology, University of Otago, PO Box 56, Dunedin 9054, New Zealand
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Watson BNJ, Easingwood RA, Tong B, Wolf M, Salmond GPC, Staals RHJ, Bostina M, Fineran PC. Different genetic and morphological outcomes for phages targeted by single or multiple CRISPR-Cas spacers. Philos Trans R Soc Lond B Biol Sci 2019; 374:20180090. [PMID: 30905290 PMCID: PMC6452268 DOI: 10.1098/rstb.2018.0090] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/07/2018] [Indexed: 01/09/2023] Open
Abstract
CRISPR-Cas systems provide bacteria and archaea with adaptive immunity against genetic invaders, such as bacteriophages. The systems integrate short sequences from the phage genome into the bacterial CRISPR array. These 'spacers' provide sequence-specific immunity but drive natural selection of evolved phage mutants that escape the CRISPR-Cas defence. Spacer acquisition occurs by either naive or primed adaptation. Naive adaptation typically results in the incorporation of a single spacer. By contrast, priming is a positive feedback loop that often results in acquisition of multiple spacers, which occurs when a pre-existing spacer matches the invading phage. We predicted that single and multiple spacers, representative of naive and primed adaptation, respectively, would cause differing outcomes after phage infection. We investigated the response of two phages, ϕTE and ϕM1, to the Pectobacterium atrosepticum type I-F CRISPR-Cas system and observed that escape from single spacers typically occurred via point mutations. Alternatively, phages escaped multiple spacers through deletions, which can occur in genes encoding structural proteins. Cryo-EM analysis of the ϕTE structure revealed shortened tails in escape mutants with tape measure protein deletions. We conclude that CRISPR-Cas systems can drive phage genetic diversity, altering morphology and fitness, through selective pressures arising from naive and primed acquisition events. This article is part of a discussion meeting issue 'The ecology and evolution of prokaryotic CRISPR-Cas adaptive immune systems'.
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Affiliation(s)
- B. N. J. Watson
- Department of Microbiology and Immunology, University of Otago, PO Box 56, Dunedin 9054, New Zealand
| | - R. A. Easingwood
- Otago Centre for Electron Microscopy, University of Otago, PO Box 56, Dunedin 9054, New Zealand
| | - B. Tong
- Department of Microbiology and Immunology, University of Otago, PO Box 56, Dunedin 9054, New Zealand
| | - M. Wolf
- Molecular Cryo-Electron Microscopy Unit, Okinawa Institute of Science and Technology, Graduate University, Onna, Okinawa, Japan
| | - G. P. C. Salmond
- Department of Biochemistry, University of Cambridge, Cambridge CB2 1QW, UK
| | - R. H. J. Staals
- Department of Microbiology and Immunology, University of Otago, PO Box 56, Dunedin 9054, New Zealand
- Laboratory of Microbiology, Department of Agrotechnology and Food Sciences, Wageningen University, 6708 HB Wageningen, The Netherlands
| | - M. Bostina
- Department of Microbiology and Immunology, University of Otago, PO Box 56, Dunedin 9054, New Zealand
- Otago Centre for Electron Microscopy, University of Otago, PO Box 56, Dunedin 9054, New Zealand
| | - P. C. Fineran
- Department of Microbiology and Immunology, University of Otago, PO Box 56, Dunedin 9054, New Zealand
- Bio-Protection Research Centre, University of Otago, Dunedin, New Zealand
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41
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Fineran PC. Resistance is not futile: bacterial 'innate' and CRISPR-Cas 'adaptive' immune systems. MICROBIOLOGY-SGM 2019; 165:834-841. [PMID: 30958259 DOI: 10.1099/mic.0.000802] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Bacteria are under a constant pressure from their viruses (phages) and other mobile genetic elements. They protect themselves through a range of defence strategies, which can be broadly classified as 'innate' and 'adaptive'. The bacterial innate immune systems include defences provided by restriction modification and abortive infection, among others. Bacterial adaptive immunity is elicited by a diverse range of CRISPR-Cas systems. Here, I discuss our research on both innate and adaptive phage resistance mechanisms and some of the evasion strategies employed by phages.
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Affiliation(s)
- Peter C Fineran
- Department of Microbiology and Immunology, University of Otago, PO Box 56, Dunedin 9054, New Zealand
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42
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Humphreys RK, Ruxton GD. Adaptive suicide: is a kin-selected driver of fatal behaviours likely? Biol Lett 2019; 15:20180823. [PMID: 30958139 PMCID: PMC6405458 DOI: 10.1098/rsbl.2018.0823] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2018] [Accepted: 02/11/2019] [Indexed: 12/21/2022] Open
Abstract
While several manipulated host behaviours are accepted as extended phenotypes of parasites, there remains debate over whether other altered behaviours in hosts following parasitic invasion represent cases of parasite manipulation, host defence or the pathology of infection. One particularly controversial subject is 'suicidal behaviour' in infected hosts. The host-suicide hypothesis proposes that host death benefits hosts doomed to reduced direct fitness by protecting kin from parasitism and therefore increasing inclusive fitness. However, adaptive suicide has been difficult to demonstrate conclusively as a host adaptation in studies on social or clonal insects, for whom high relatedness should enable greater inclusive fitness benefits. Following discussion of empirical and theoretical works from a behavioural ecology perspective, this review finds that the most persuasive evidence for selection of adaptive suicide comes from bacteria. Despite a focus on parasites, driven by the existing literature, the potential for the evolution of adaptive suicidal behaviour in hosts is also considered to apply to cases of infection by pathogens, provided that the disease has a severe effect on direct fitness and that suicidal behaviour can affect pathogen transmission dynamics. Suggestions are made for future research and a broadening of the possible implications for coevolution between parasites and hosts.
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Affiliation(s)
- Rosalind K. Humphreys
- School of Biology, University of St Andrews, Dyer's Brae House, St Andrews, Fife KY16 9TH, UK
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43
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Czajkowski R. May the Phage be With You? Prophage-Like Elements in the Genomes of Soft Rot Pectobacteriaceae: Pectobacterium spp. and Dickeya spp. Front Microbiol 2019; 10:138. [PMID: 30828320 PMCID: PMC6385640 DOI: 10.3389/fmicb.2019.00138] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2018] [Accepted: 01/21/2019] [Indexed: 12/20/2022] Open
Abstract
Soft Rot Pectobacteriaceae (SRP; Pectobacterium spp. and Dickeya spp., formerly known as pectinolytic Erwinia spp.) are necrotrophic bacterial pathogens infecting a large number of plant species worldwide, including agriculturally-important crops. Despite the SRP importance in agriculture, little is known about the bacteriophages infecting them, and even less about the prophages present in their genomes. Prophages are recognized as factors underlying bacterial virulence, genomic diversification and ecological fitness that contribute to the novel phenotypic properties of bacterial hosts. Likewise, they are recognized as a driving force of bacterial evolution. In this study, 57 complete genomes of Pectobacterium spp. and Dickeya spp. deposited in NCBI GenBank, were analyzed for the presence of prophage-like elements. Viral sequences were discovered in 95% of bacterial genomes analyzed with the use of PHASTER, PhiSpy, and manual curation of the candidate sequences using NCBI BLAST. In total 37 seemingly intact and 48 putatively defective prophages were found. The 37 seemingly intact prophages (27 sequences in Dickeya spp. genomes and 10 sequences in Pectobacterium spp. genomes) were annotated using RAST. Analysis of the prophage genes encoding viral structural proteins allowed classification of these prophages into different families of the order Caudovirales (tailed bacteriophages) with the SRP prophages of the Myoviridae family (81% of found prophages) being the most abundant. The phylogenetic relationships between prophages were analyzed using amino acid sequences of terminase large subunit (gene terL), integrase (gene int), holin (gene hol), and lysin (gene lys). None of these markers however proved fully useful for clear phylogenetic separation of prophages of SRP into distinct clades. Comparative analyses of prophage proteomes revealed six clusters: five present in Dickeya spp. and one within Pectobacterium spp. When screened for the presence of bacterial genes in the genomes of intact prophages, only one prophage did not contain any ORFs of bacterial origin, the other prophages contained up to 23 genes acquired from bacterial hosts. The bacterial genes present in prophages could possibly affect fitness and virulence of their hosts. The implication of prophage presence in the genomes of Pectobacterium spp. and Dickeya spp. is discussed.
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Affiliation(s)
- Robert Czajkowski
- Laboratory of Biologically Active Compounds, Intercollegiate Faculty of Biotechnology of University of Gdansk and Medical University of Gdansk, University of Gdansk, Gdansk, Poland
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A Systematic Overview of Type II and III Toxin-Antitoxin Systems with a Focus on Druggability. Toxins (Basel) 2018; 10:toxins10120515. [PMID: 30518070 PMCID: PMC6315513 DOI: 10.3390/toxins10120515] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2018] [Revised: 11/29/2018] [Accepted: 11/30/2018] [Indexed: 02/07/2023] Open
Abstract
Toxin-antitoxin (TA) systems are known to play various roles in physiological processes, such as gene regulation, growth arrest and survival, in bacteria exposed to environmental stress. Type II TA systems comprise natural complexes consisting of protein toxins and antitoxins. Each toxin and antitoxin participates in distinct regulatory mechanisms depending on the type of TA system. Recently, peptides designed by mimicking the interfaces between TA complexes showed its potential to activate the activity of toxin by competing its binding counterparts. Type II TA systems occur more often in pathogenic bacteria than in their nonpathogenic kin. Therefore, they can be possible drug targets, because of their high abundance in some pathogenic bacteria, such as Mycobacterium tuberculosis. In addition, recent bioinformatic analyses have shown that type III TA systems are highly abundant in the intestinal microbiota, and recent clinical studies have shown that the intestinal microbiota is linked to inflammatory diseases, obesity and even several types of cancer. We therefore focused on exploring the putative relationship between intestinal microbiota-related human diseases and type III TA systems. In this paper, we review and discuss the development of possible druggable materials based on the mechanism of type II and type III TA system.
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45
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Walling LR, Butler JS. Toxins targeting transfer RNAs: Translation inhibition by bacterial toxin-antitoxin systems. WILEY INTERDISCIPLINARY REVIEWS-RNA 2018; 10:e1506. [PMID: 30296016 DOI: 10.1002/wrna.1506] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2018] [Revised: 08/07/2018] [Accepted: 08/13/2018] [Indexed: 01/09/2023]
Abstract
Prokaryotic toxin-antitoxin (TA) systems are composed of a protein toxin and its cognate antitoxin. These systems are abundant in bacteria and archaea and play an important role in growth regulation. During favorable growth conditions, the antitoxin neutralizes the toxin's activity. However, during conditions of stress or starvation, the antitoxin is inactivated, freeing the toxin to inhibit growth and resulting in dormancy. One mechanism of growth inhibition used by several TA systems results from targeting transfer RNAs (tRNAs), either through preventing aminoacylation, acetylating the primary amino group, or endonucleolytic cleavage. All of these mechanisms inhibit translation and result in growth arrest. Many of these toxins only act on a specific tRNA or a specific subset of tRNAs; however, more work is necessary to understand the specificity determinants of these toxins. For the toxins whose specificity has been characterized, both sequence and structural components of the tRNA appear important for recognition by the toxin. Questions also remain regarding the mechanisms used by dormant bacteria to resume growth after toxin induction. Rescue of stalled ribosomes by transfer-messenger RNAs, removal of acetylated amino groups from tRNAs, or ligation of cleaved RNA fragments have all been implicated as mechanisms for reversing toxin-induced dormancy. However, the mechanisms of resuming growth after induction of the majority of tRNA targeting toxins are not yet understood. This article is categorized under: Translation > Translation Regulation RNA in Disease and Development > RNA in Disease RNA Interactions with Proteins and Other Molecules > Protein-RNA Recognition.
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Affiliation(s)
- Lauren R Walling
- Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, New York
| | - J Scott Butler
- Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, New York.,Department of Biochemistry and Biophysics, University of Rochester Medical Center, Rochester, New York.,Center for RNA Biology, University of Rochester Medical Center, Rochester, New York
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46
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Shneider MM, Kabanova AP, Korzhenkov AA, Miroshnikov KK, Vo Thi NH, Toshchakov SV, Miroshnikov KA, Ignatov AN. Draft Genome Sequence of Pectobacterium atrosepticum PB72 and Complete Genome Sequence of the Specific Bacteriophage PP90. GENOME ANNOUNCEMENTS 2018; 6:e00473-18. [PMID: 29976602 PMCID: PMC6033984 DOI: 10.1128/genomea.00473-18] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 04/30/2018] [Accepted: 06/04/2018] [Indexed: 11/20/2022]
Abstract
We present the draft genome sequence of Pectobacterium atrosepticum strain PB72 infecting potatoes in Russia. PB72 is similar to the previously reported strain 21A. Considering potential biocontrol of this pathogen, an infectious bacteriophage was isolated and characterized. Phage vB_PatP_PP90 is a lytic podovirus of narrow host range belonging to the KP34virus genus.
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Affiliation(s)
- Mikhail M Shneider
- Shemyakin & Ovchinnikov Institute of Bioorganic Chemistry RAS, Moscow, Russia
| | - Anastasia P Kabanova
- Shemyakin & Ovchinnikov Institute of Bioorganic Chemistry RAS, Moscow, Russia
- PhytoEngineering R&D Center, LLC, Moscow Region, Russia
| | | | - Kirill K Miroshnikov
- Winogradsky Institute of Microbiology, Research Center of Biotechnology RAS, Moscow, Russia
| | | | - Stepan V Toshchakov
- Immanuel Kant Baltic Federal University, Kaliningrad, Russia
- Winogradsky Institute of Microbiology, Research Center of Biotechnology RAS, Moscow, Russia
| | - Konstantin A Miroshnikov
- Shemyakin & Ovchinnikov Institute of Bioorganic Chemistry RAS, Moscow, Russia
- PhytoEngineering R&D Center, LLC, Moscow Region, Russia
| | - Alexander N Ignatov
- PhytoEngineering R&D Center, LLC, Moscow Region, Russia
- Peoples' Friendship University of Russia, Moscow, Russia
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47
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Watson BNJ, Staals RHJ, Fineran PC. CRISPR-Cas-Mediated Phage Resistance Enhances Horizontal Gene Transfer by Transduction. mBio 2018; 9:e02406-17. [PMID: 29440578 PMCID: PMC5821089 DOI: 10.1128/mbio.02406-17] [Citation(s) in RCA: 77] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2018] [Accepted: 01/17/2018] [Indexed: 12/27/2022] Open
Abstract
A powerful contributor to prokaryotic evolution is horizontal gene transfer (HGT) through transformation, conjugation, and transduction, which can be advantageous, neutral, or detrimental to fitness. Bacteria and archaea control HGT and phage infection through CRISPR-Cas (clustered regularly interspaced short palindromic repeats-CRISPR-associated proteins) adaptive immunity. Although the benefits of resisting phage infection are evident, this can come at a cost of inhibiting the acquisition of other beneficial genes through HGT. Despite the ability of CRISPR-Cas to limit HGT through conjugation and transformation, its role in transduction is largely overlooked. Transduction is the phage-mediated transfer of bacterial DNA between cells and arguably has the greatest impact on HGT. We demonstrate that in Pectobacterium atrosepticum, CRISPR-Cas can inhibit the transduction of plasmids and chromosomal loci. In addition, we detected phage-mediated transfer of a large plant pathogenicity genomic island and show that CRISPR-Cas can inhibit its transduction. Despite these inhibitory effects of CRISPR-Cas on transduction, its more common role in phage resistance promotes rather than diminishes HGT via transduction by protecting bacteria from phage infection. This protective effect can also increase transduction of phage-sensitive members of mixed populations. CRISPR-Cas systems themselves display evidence of HGT, but little is known about their lateral dissemination between bacteria and whether transduction can contribute. We show that, through transduction, bacteria can acquire an entire chromosomal CRISPR-Cas system, including cas genes and phage-targeting spacers. We propose that the positive effect of CRISPR-Cas phage immunity on enhancing transduction surpasses the rarer cases where gene flow by transduction is restricted.IMPORTANCE The generation of genetic diversity through acquisition of DNA is a powerful contributor to microbial evolution and occurs through transformation, conjugation, and transduction. Of these, transduction, the phage-mediated transfer of bacterial DNA, is arguably the major route for genetic exchange. CRISPR-Cas adaptive immune systems control gene transfer by conjugation and transformation, but transduction has been mostly overlooked. Our results indicate that CRISPR-Cas can impede, but typically enhances the transduction of plasmids, chromosomal genes, and pathogenicity islands. By limiting wild-type phage replication, CRISPR-Cas immunity increases transduction in both phage-resistant and -sensitive members of mixed populations. Furthermore, we demonstrate mobilization of a chromosomal CRISPR-Cas system containing phage-targeting spacers by generalized transduction, which might partly account for the uneven distribution of these systems in nature. Overall, the ability of CRISPR-Cas to promote transduction reveals an unexpected impact of adaptive immunity on horizontal gene transfer, with broader implications for microbial evolution.
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Affiliation(s)
- Bridget N J Watson
- Department of Microbiology and Immunology, University of Otago, Dunedin, New Zealand
| | - Raymond H J Staals
- Department of Microbiology and Immunology, University of Otago, Dunedin, New Zealand
- Laboratory of Microbiology, Wageningen University, Wageningen, The Netherlands
| | - Peter C Fineran
- Department of Microbiology and Immunology, University of Otago, Dunedin, New Zealand
- Bio-Protection Research Centre, University of Otago, Dunedin, New Zealand
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48
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Short FL, Akusobi C, Broadhurst WR, Salmond GPC. The bacterial Type III toxin-antitoxin system, ToxIN, is a dynamic protein-RNA complex with stability-dependent antiviral abortive infection activity. Sci Rep 2018; 8:1013. [PMID: 29343718 PMCID: PMC5772629 DOI: 10.1038/s41598-017-18696-x] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2017] [Accepted: 12/12/2017] [Indexed: 12/03/2022] Open
Abstract
Bacteria have evolved numerous defense systems to protect themselves from viral (bacteriophage) infection. The ToxIN system of Pectobacterium atrosepticum is a Type III toxin-antitoxin complex and “altruistic suicide” anti-phage system, which kills phage-infected cells through the release of a ribonuclease toxin, ToxN. ToxN is counteracted by a co-transcribed antitoxic RNA pseudoknot, ToxI, which self-assembles with ToxN into an inactive 3 ToxI:3 ToxN complex in vitro. However it is not known whether this complex is predominant in vivo, or how the complex is disassembled following infection to trigger a lethal, “altruistic” response. In this study, we characterise ToxI turnover and folding, and explore the link between complex stability and anti-phage activity, with a view to understanding events that lead to ToxN-mediated suicide following phage infection. We present evidence that ToxN constantly cleaves fresh ToxI in vivo rather than staying associated with pre-processed antitoxin, and that the ToxI antitoxin can partially fold spontaneously using conserved nucleotides. We also show that reducing the stability of the ToxIN complex can increase the strength of the antiviral response in a phage-dependent manner. Based on this information, we propose a revised model for ToxN inhibition, complex assembly and activation by infecting bacteriophage.
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Affiliation(s)
- Francesca L Short
- Department of Biochemistry, Hopkins Building, Downing Site, Tennis Court Road, University of Cambridge, Cambridge, CB2 1QW, UK.,Wellcome Trust Sanger Institute, Genome Campus, Hinxton, CB10 1SA, UK
| | - Chidiebere Akusobi
- Department of Biochemistry, Hopkins Building, Downing Site, Tennis Court Road, University of Cambridge, Cambridge, CB2 1QW, UK.,Department of Immunology and Infectious Diseases, Harvard T. H. Chan School of Public Health, Boston, Massachusetts, USA
| | - William R Broadhurst
- Department of Biochemistry, Hopkins Building, Downing Site, Tennis Court Road, University of Cambridge, Cambridge, CB2 1QW, UK
| | - George P C Salmond
- Department of Biochemistry, Hopkins Building, Downing Site, Tennis Court Road, University of Cambridge, Cambridge, CB2 1QW, UK.
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49
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Pawluk A, Davidson AR, Maxwell KL. Anti-CRISPR: discovery, mechanism and function. Nat Rev Microbiol 2017; 16:12-17. [DOI: 10.1038/nrmicro.2017.120] [Citation(s) in RCA: 231] [Impact Index Per Article: 33.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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Shidore T, Triplett LR. Toxin-Antitoxin Systems: Implications for Plant Disease. ANNUAL REVIEW OF PHYTOPATHOLOGY 2017; 55:161-179. [PMID: 28525308 DOI: 10.1146/annurev-phyto-080516-035559] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Toxin-antitoxin (TA) systems are gene modules that are ubiquitous in free-living prokaryotes. Diverse in structure, cellular function, and fitness roles, TA systems are defined by the presence of a toxin gene that suppresses bacterial growth and a toxin-neutralizing antitoxin gene, usually encoded in a single operon. Originally viewed as DNA maintenance modules, TA systems are now thought to function in many roles, including bacterial stress tolerance, virulence, phage defense, and biofilm formation. However, very few studies have investigated the significance of TA systems in the context of plant-microbe interactions. This review discusses the potential impact and application of TA systems in plant-associated bacteria, guided by insights gained from animal-pathogenic model systems.
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Affiliation(s)
- T Shidore
- Department of Plant Pathology and Ecology, The Connecticut Agricultural Experiment Station, New Haven, Connecticut 06511:
| | - L R Triplett
- Department of Plant Pathology and Ecology, The Connecticut Agricultural Experiment Station, New Haven, Connecticut 06511:
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