The process by which bacterial populations evolve to adapt to new hosts is broadly important and still uncertain. We study two key parts of this process: the nature and trajectories of beneficial mutations, and the eco-evolutionary dynamics that emerge when bacteria form biofilm communities. Identifying and tracking the spread of beneficial mutations has been empowered by contemporary genomics, and has allowed us to find commonalities among beneficial mutations in many evolving bacterial systems. Our study of biofilms has been aided by a simple model enabling long-term evolution in a biofilm life cycle. Focusing on bacteria of the Burkholderia cepacia complex and Pseudomonas aeruginosa, we find this model surprisingly selects for mutations in genes that commonly mutate during chronic infections of the cystic fibrosis airway and in wounds. This system also selects for persistent genetic diversity that reflect adaptations to different biofilm niches. More recently, we have been studying more rapid evolution of bacteria exposed to stronger selection like antibiotics or specific host association, often in vivo. In these conditions, we find strongly parallel mutations that show functional details of the traits that underlie adaptation. Further, growing cases of strong parallelism raise the probability that evolution may be predictable and useful to solve problems in medicine like drug resistance. Last and most important, we have used the simplicity of our biofilm model to develop a curriculum in high school classes to allow introductory biology students to learn key concepts in evolution and heredity by doing an evolution experiment. Both this curriculum and clear examples of evolution-in-action during infections offer the promise of broader appreciation of the utility of evolutionary biology.

View YouTube video of seminar: https://youtu.be/l7JHJ5eZLfM