Shared mechanisms of enhanced plasmid maintenance and antibiotic tolerance mediated by the VapBC toxin:antitoxin system

TY - JOUR

T1 - Shared mechanisms of enhanced plasmid maintenance and antibiotic tolerance mediated by the VapBC toxin:antitoxin system

AU - Hollingshead, Sarah

AU - McVicker, Gareth

AU - Nielsen, Maria R

AU - Zhang, YuGeng

AU - Pilla, Giulia

AU - Jones, Rebekah A

AU - Thomas, Jonathan C

AU - Johansen, Sarah E H

AU - Exley, Rachel M

AU - Brodersen, Ditlev E

AU - Tang, Christoph M

PY - 2025/2

Y1 - 2025/2

N2 - 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.

AB - 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.

KW - Shigella

KW - TA systems

KW - VapBC

KW - antibiotic tolerance

KW - plasmid stability

UR - http://www.scopus.com/inward/record.url?scp=85217816080&partnerID=8YFLogxK

U2 - 10.1128/mbio.02616-24

DO - 10.1128/mbio.02616-24

M3 - Journal article

C2 - 39704502

SN - 2161-2129

VL - 16

SP - e0261624

JO - mBio

JF - mBio

IS - 2

ER -