Genomic Background Governs Opposing Responses to Nalidixic Acid Upon Megaplasmid Acquisition in Pseudomonas

David A. Baltrus, Caitlin Smith, MacKenzie Derrick, Courtney Leligdon, Zoe Rosenthal, Madison Mollico, Andrew Moore, Meara Clark

Research output: Contribution to journalArticlepeer-review


Horizontal Gene Transfer is a significant driver of evolutionary dynamics across microbial populations. Although the benefits of the acquisition of new genetic material are often quite clear, it has also been demonstrated across various systems that gene transfer events can cause significant phenotypic changes and entail fitness costs depending on the environmental context. Here we test for the generality of one of these costs, sensitization of cells to the antibiotic nalidixic acid after acquisition of a ~1Mb megaplasmid across Pseudomonas strains and species. Overall, we find that the presence of this megaplasmid sensitizes many different strains to nalidixic acid, but that this same horizontal gene transfer event actually increases resistance of Pseudomonas putida KT2440 to this antibiotic. These results are not easily explained away as secondary consequences of overall fitness effects, and the effects do not appear to be correlated with sensitization to ciprofloxacin. Lastly, we draw parallels between these reported results and the phenomenon of sign epistasis for de novo mutations and explore how context dependence of effects of plasmid acquisition could impact overall evolutionary dynamics and the evolution of antimicrobial resistance.

Original languageEnglish (US)
JournalUnknown Journal
StatePublished - Nov 6 2019

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)
  • Agricultural and Biological Sciences(all)
  • Immunology and Microbiology(all)
  • Neuroscience(all)
  • Pharmacology, Toxicology and Pharmaceutics(all)

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