Gene, Organism and Environment: Understanding Patterns of Genome Evolution in Bacteria and Bacteriophage

For my dissertation research, I used a model system of bacteria and bacteriophage to study patterns of genome evolution. I performed whole-genome sequencing of replicate populations to determine the genetic changes responsible for a repeatable pattern of coevolution between bacteria and phage. I found that genetic changes conferring resistance in bacteria negatively impacted other traits such as growth rates and sensitivity to antibiotic. Different resistance mutations varied in the magnitude of their pleiotropic costs, and this resulted in a fixation bias favoring mutations that minimized pleiotropic effects. I manipulated the environment and found that differential pleiotropy between environments drove repeatable evolution at different genetic scales. Finally, I explored theoretically how bacteria, phage, and resource interact through a dynamic system of feedbacks. I used a mathematical model to describe priority effects in evolution, where the expected fate of a beneficial mutation varies depending upon whether it appears before or after a competing mutation.10000-01-0