Abstracts (first author)
Effect of Phages on the Cost of Antibiotic Resistance
Experimental studies of antibiotic resistance evolution typically employ a single bacterial species in pure culture. However, outside the laboratory, parasitism of bacteria by viruses (phages) is ubiquitous. I used experimental populations of Escherichia coli to show that phage parasitism altered the outcomes of competitions between antibiotic-resistant and sensitive genotypes. Phages caused rapid selective sweeps, associated with the emergence of phage-resistant mutants, and this was approximately equally likely to favour antibiotic-resistant or sensitive genotypes when their initial frequencies were similar. An elevated mutation rate was advantageous in the presence of phages, suggesting that a given antibiotic-resistant or sensitive genotype is more likely to fix under phage parasitism when it has a high mutation supply rate relative to other genotypes. Given their abundance in nature, phages probably modify selection on other traits in many different scenarios.