GELIFES Seminars - Vaughn Cooper

Vaughn Cooper (University of Pittsburgh)

The evolutionary biology of Pseudomonas aeruginosa infections lasting days or years

Opportunistic bacterial pathogens are, by definition, not adapted to any specific host. Rather, they exploit vulnerabilities in various eukaryotes they encounter and employ their flexible physiology and life-history to colonize and reproduce using host resources. At some point, intrinsic plasticity becomes limiting, however, and mutants in the opportunistic population encounter strong selection that enrich locally adapted genotypes. The timing, diversity, and genetic pathways to adaptations by opportunists are mostly undescribed and are the focus of this talk. I will focus on two studies of the archetypical opportunist Pseudomonas aeruginosa evolving during infections. In the first, we study how different P. aeruginosa strains compete and adaptively evolve during a monthlong wound infection, and find that adaptations by winning strains that promote biofilm growth are predominantly encoded by bacteriophage released by losing strains. In the second, we track P. aeruginosa populations as they adapt over years in the sinuses of persons with cystic fibrosis, and find that the most “pathoadapted” lineages undergo a process of genome erosion caused initially by mutations that promote aggregation, which reduces their population sizes and enhances genetic drift. Together, these studies demonstrate that the earliest adaptations by opportunists involve changes in aggregation that enhance adherence to host tissues and avoid immunity, but these may come at a longer-term cost of accelerated genome erosion, much as is seen in symbiotic bacteria.

Biosketch
The primary goal of our laboratory is to understand how bacterial populations evolve and adapt to colonize hosts and cause disease. By studying evolution-in-action, both in experimental populations and in ongoing infections, and using the latest methods in genomic sequencing, we seek to identify mechanisms of bacterial adaptation in vitro and in vivo. We are particularly focused on how bacterial populations form complex communities within biofilms and how cells perceive cues to attach or disperse. We are also developing genome-based diagnostics for bacterial infections.

Link to seminar