Shared mechanisms of enhanced plasmid maintenance and antibiotic tolerance mediated by the VapBC toxin:antitoxin system
ABSTRACT Toxin:antitoxin (TA) systems are widespread in bacteria and were first identified as plasmid addiction systems that kill bacteria lacking a TA-encoding plasmid following cell division. TA systems have also been implicated in bacterial persistence and antibiotic tolerance, which can be precu...
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American Society for Microbiology
2025-02-01
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| Online Access: | https://journals.asm.org/doi/10.1128/mbio.02616-24 |
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| author | Sarah Hollingshead Gareth McVicker Maria R. Nielsen YuGeng Zhang Giulia Pilla Rebekah A. Jones Jonathan C. Thomas Sarah E. H. Johansen Rachel M. Exley Ditlev E. Brodersen Christoph M. Tang |
| author_facet | Sarah Hollingshead Gareth McVicker Maria R. Nielsen YuGeng Zhang Giulia Pilla Rebekah A. Jones Jonathan C. Thomas Sarah E. H. Johansen Rachel M. Exley Ditlev E. Brodersen Christoph M. Tang |
| author_sort | Sarah Hollingshead |
| collection | DOAJ |
| description | ABSTRACT Toxin:antitoxin (TA) systems are widespread in bacteria and were first identified as plasmid addiction systems that kill bacteria lacking a TA-encoding plasmid following cell division. TA systems have also been implicated in bacterial persistence and antibiotic tolerance, which can be precursors of antibiotic resistance. Here, we identified a clinical isolate of Shigella sonnei (CS14) with a remarkably stable pINV virulence plasmid; pINV is usually frequently lost from S. sonnei, but plasmid loss was not detected from CS14. We found that the plasmid in CS14 is stabilized by a single nucleotide polymorphism (SNP) in its vapBC TA system. VapBC TA systems are the most common Type II TA system in bacteria, and consist of a VapB antitoxin and VapC PIN domain-containing toxin. The plasmid stabilizing SNP leads to a Q12L substitution in the DNA-binding domain of VapB, which reduces VapBC binding to its own promoter, impairing vapBC autorepression. However, VapBL12C mediates high-level plasmid stabilization because VapBL12 is more prone to degradation by Lon than wild-type VapB; this liberates VapC to efficiently kill bacteria that no longer contain a plasmid. Of note, mutations that confer tolerance to antibiotics in Escherichia coli also map to the DNA-binding domain of VapBC encoded by the chromosomally integrated F plasmid. We demonstrate that the tolerance mutations also enhance plasmid stabilization by the same mechanism as VapBL12. Our findings highlight the links between plasmid maintenance and antibiotic tolerance, both of which can promote the development of antimicrobial resistance.IMPORTANCEOur work addresses two processes, the maintenance of plasmids and antibiotic tolerance; both contribute to the development of antimicrobial resistance in bacteria that cause human disease. Here, we found a single nucleotide change in the vapBC toxin:antitoxin system that stabilizes the large virulence plasmid of Shigella sonnei. The mutation is in the vapB antitoxin gene and makes the antitoxin more likely to be degraded, releasing the VapC toxin to efficiently kill cells without the plasmid (and thus unable to produce more antitoxin as an antidote). We found that vapBC mutations in E. coli that lead to antibiotic tolerance (a precursor to resistance) also operate by the same mechanism (i.e., generating VapB that is prone to cleavage); free VapC during tolerance will arrest bacterial growth and prevent susceptibility to antibiotics. This work shows the mechanistic links between plasmid maintenance and tolerance, and has applications in biotech and in the design and evaluation of vaccines against shigellosis. |
| format | Article |
| id | doaj-art-380536adc2364bd4bed4b74f9f5e0ead |
| institution | Kabale University |
| issn | 2150-7511 |
| language | English |
| publishDate | 2025-02-01 |
| publisher | American Society for Microbiology |
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| series | mBio |
| spelling | doaj-art-380536adc2364bd4bed4b74f9f5e0ead2025-02-05T14:00:48ZengAmerican Society for MicrobiologymBio2150-75112025-02-0116210.1128/mbio.02616-24Shared mechanisms of enhanced plasmid maintenance and antibiotic tolerance mediated by the VapBC toxin:antitoxin systemSarah Hollingshead0Gareth McVicker1Maria R. Nielsen2YuGeng Zhang3Giulia Pilla4Rebekah A. Jones5Jonathan C. Thomas6Sarah E. H. Johansen7Rachel M. Exley8Ditlev E. Brodersen9Christoph M. Tang10Sir William Dunn School of Pathology, University of Oxford, Oxford, United KingdomDepartment of Biosciences, Nottingham Trent University, Nottingham, United KingdomDepartment of Molecular Biology and Genetics, Aarhus University, Aarhus, DenmarkSir William Dunn School of Pathology, University of Oxford, Oxford, United KingdomSir William Dunn School of Pathology, University of Oxford, Oxford, United KingdomSir William Dunn School of Pathology, University of Oxford, Oxford, United KingdomDepartment of Biosciences, Nottingham Trent University, Nottingham, United KingdomDepartment of Molecular Biology and Genetics, Aarhus University, Aarhus, DenmarkSir William Dunn School of Pathology, University of Oxford, Oxford, United KingdomDepartment of Molecular Biology and Genetics, Aarhus University, Aarhus, DenmarkSir William Dunn School of Pathology, University of Oxford, Oxford, United KingdomABSTRACT Toxin:antitoxin (TA) systems are widespread in bacteria and were first identified as plasmid addiction systems that kill bacteria lacking a TA-encoding plasmid following cell division. TA systems have also been implicated in bacterial persistence and antibiotic tolerance, which can be precursors of antibiotic resistance. Here, we identified a clinical isolate of Shigella sonnei (CS14) with a remarkably stable pINV virulence plasmid; pINV is usually frequently lost from S. sonnei, but plasmid loss was not detected from CS14. We found that the plasmid in CS14 is stabilized by a single nucleotide polymorphism (SNP) in its vapBC TA system. VapBC TA systems are the most common Type II TA system in bacteria, and consist of a VapB antitoxin and VapC PIN domain-containing toxin. The plasmid stabilizing SNP leads to a Q12L substitution in the DNA-binding domain of VapB, which reduces VapBC binding to its own promoter, impairing vapBC autorepression. However, VapBL12C mediates high-level plasmid stabilization because VapBL12 is more prone to degradation by Lon than wild-type VapB; this liberates VapC to efficiently kill bacteria that no longer contain a plasmid. Of note, mutations that confer tolerance to antibiotics in Escherichia coli also map to the DNA-binding domain of VapBC encoded by the chromosomally integrated F plasmid. We demonstrate that the tolerance mutations also enhance plasmid stabilization by the same mechanism as VapBL12. Our findings highlight the links between plasmid maintenance and antibiotic tolerance, both of which can promote the development of antimicrobial resistance.IMPORTANCEOur work addresses two processes, the maintenance of plasmids and antibiotic tolerance; both contribute to the development of antimicrobial resistance in bacteria that cause human disease. Here, we found a single nucleotide change in the vapBC toxin:antitoxin system that stabilizes the large virulence plasmid of Shigella sonnei. The mutation is in the vapB antitoxin gene and makes the antitoxin more likely to be degraded, releasing the VapC toxin to efficiently kill cells without the plasmid (and thus unable to produce more antitoxin as an antidote). We found that vapBC mutations in E. coli that lead to antibiotic tolerance (a precursor to resistance) also operate by the same mechanism (i.e., generating VapB that is prone to cleavage); free VapC during tolerance will arrest bacterial growth and prevent susceptibility to antibiotics. This work shows the mechanistic links between plasmid maintenance and tolerance, and has applications in biotech and in the design and evaluation of vaccines against shigellosis.https://journals.asm.org/doi/10.1128/mbio.02616-24Shigellaplasmid stabilityantibiotic toleranceTA systemsVapBC |
| spellingShingle | Sarah Hollingshead Gareth McVicker Maria R. Nielsen YuGeng Zhang Giulia Pilla Rebekah A. Jones Jonathan C. Thomas Sarah E. H. Johansen Rachel M. Exley Ditlev E. Brodersen Christoph M. Tang Shared mechanisms of enhanced plasmid maintenance and antibiotic tolerance mediated by the VapBC toxin:antitoxin system mBio Shigella plasmid stability antibiotic tolerance TA systems VapBC |
| title | Shared mechanisms of enhanced plasmid maintenance and antibiotic tolerance mediated by the VapBC toxin:antitoxin system |
| title_full | Shared mechanisms of enhanced plasmid maintenance and antibiotic tolerance mediated by the VapBC toxin:antitoxin system |
| title_fullStr | Shared mechanisms of enhanced plasmid maintenance and antibiotic tolerance mediated by the VapBC toxin:antitoxin system |
| title_full_unstemmed | Shared mechanisms of enhanced plasmid maintenance and antibiotic tolerance mediated by the VapBC toxin:antitoxin system |
| title_short | Shared mechanisms of enhanced plasmid maintenance and antibiotic tolerance mediated by the VapBC toxin:antitoxin system |
| title_sort | shared mechanisms of enhanced plasmid maintenance and antibiotic tolerance mediated by the vapbc toxin antitoxin system |
| topic | Shigella plasmid stability antibiotic tolerance TA systems VapBC |
| url | https://journals.asm.org/doi/10.1128/mbio.02616-24 |
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