A Moving Target: The Megaplasmid pMPPla107 Sensitizes Cells to an Inhibitory Agent Conserved Across Pseudomonas spp.

The widespread use of antibiotics across clinical and agricultural settings results in strong selection pressures and contributes to the fixation of antibiotic resistance genes, the presence of which lowers the efficacy of proven treatments for infection. Furthermore, plasmids are often key vectors that facilitate the rapid dispersal of antibiotic resistance genes across bacterial strains via horizontal gene transfer. In contrast to previous widespread correlations between plasmid acquisition and resistance to antimicrobial compounds, we demonstrate that acquisition of the P. syringae megaplasmid pMPPla107 sensitizes strains to a conserved, bacteriostatic small molecule produced by many Pseudomonas spp. Moreover, we find the acquisition of pMPPla107 reduces production of the inhibitory agent. Our results provide insights and suggest new directions to investigate collateral sensitivity to antimicrobials due to plasmid acquisition as well as highlight costs associated to horizontal gene transfer in the form of sensitivity to antagonistic microbial interactions.