title: Evolutionary Paths That Expand Plasmid Host-Range: Implications for Spread of Antibiotic Resistance.
abstract: The World Health Organization has declared the emergence of antibiotic resistance to be a global threat to human health. Broad-host-range plasmids have a key role in causing this health crisis because they transfer multiple resistance genes to a wide range of bacteria. To limit the spread of antibiotic resistance, we need to gain insight into the mechanisms by which the host range of plasmids evolves. Although initially unstable plasmids have been shown to improve their persistence through evolution of the plasmid, the host, or both, the means by which this occurs are poorly understood. Here, we sought to identify the underlying genetic basis of expanded plasmid host-range and increased persistence of an antibiotic resistance plasmid using a combined experimental-modeling approach that included whole-genome resequencing, molecular genetics and a plasmid population dynamics model. In nine of the ten previously evolved clones, changes in host and plasmid each slightly improved plasmid persistence, but their combination resulted in a much larger improvement, which indicated positive epistasis. The only genetic change in the plasmid was the acquisition of a transposable element from a plasmid native to the Pseudomonas host used in these studies. The analysis of genetic deletions showed that the critical genes on this transposon encode a putative toxin-antitoxin (TA) and a cointegrate resolution system. As evolved plasmids were able to persist longer in multiple naïve hosts, acquisition of this transposon also expanded the plasmid's host range, which has important implications for the spread of antibiotic resistance.
authors.affiliation: Department of Biological Sciences, University of Idaho Institute for Bioinformatics and Evolutionary Studies (IBEST), University of Idaho.
authors.forename: Wesley
authors.initials: W
authors.lastname: Loftie-Eaton
authors.affiliation: Department of Biological Sciences, University of Idaho Institute for Bioinformatics and Evolutionary Studies (IBEST), University of Idaho.
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Yano
authors.affiliation: Department of Biological Sciences, University of Idaho.
authors.forename: Stephen
authors.initials: S
authors.lastname: Burleigh
authors.affiliation: Department of Biological Sciences, University of Idaho.
authors.forename: Ryan S
authors.initials: RS
authors.lastname: Simmons
authors.affiliation: Department of Biological Sciences, University of Idaho Institute for Bioinformatics and Evolutionary Studies (IBEST), University of Idaho.
authors.forename: Julie M
authors.initials: JM
authors.lastname: Hughes
authors.affiliation: Department of Biological Sciences, University of Idaho Institute for Bioinformatics and Evolutionary Studies (IBEST), University of Idaho.
authors.forename: Linda M
authors.initials: LM
authors.lastname: Rogers
authors.affiliation: Institute for Bioinformatics and Evolutionary Studies (IBEST), University of Idaho.
authors.forename: Samuel S
authors.initials: SS
authors.lastname: Hunter
authors.affiliation: Department of Biological Sciences, University of Idaho Institute for Bioinformatics and Evolutionary Studies (IBEST), University of Idaho.
authors.forename: Matthew L
authors.initials: ML
authors.lastname: Settles
authors.affiliation: Department of Biological Sciences, University of Idaho Institute for Bioinformatics and Evolutionary Studies (IBEST), University of Idaho.
authors.forename: Larry J
authors.initials: LJ
authors.lastname: Forney
authors.affiliation: Department of Biology, University of Florida josemi@ufl.edu evatop@uidaho.edu.
authors.forename: José M
authors.initials: JM
authors.lastname: Ponciano
authors.affiliation: Department of Biological Sciences, University of Idaho Institute for Bioinformatics and Evolutionary Studies (IBEST), University of Idaho josemi@ufl.edu evatop@uidaho.edu.
authors.forename: Eva M
authors.initials: EM
authors.lastname: Top
mesh_terms: D004251:DNA Transposable Elements / Q000235:genetics; D004352:Drug Resistance, Microbial / Q000235:genetics*; D019143:Evolution, Molecular; D058507:Host Specificity / Q000235:genetics; D054884:Host-Pathogen Interactions / Q000235:genetics; D006801:Humans; D010957:Plasmids / Q000235:genetics*; D011549:Pseudomonas / Q000187:drug effects / Q000235:genetics* / Q000472:pathogenicity; D017422:Sequence Analysis, DNA
chemical_list: D004251:DNA Transposable Elements
keywords: Pseudomonas; antibiotic resistance; broad host range plasmid; epistasis; experimental evolution; horizontal gene transfer; resolvase; toxin–antitoxin; transposon