CAREER: The evolutionary genetics of constraint and evolvability in an RNA bacteriophage

The goal of this project is to study how interactions among genes limits evolution. Using viruses that only infect bacteria, the steps that viruses take when infecting and adapting to new hosts will be studied. Understanding evolutionary limits is especially important for viruses as they can be threats to the health of humans, livestock, and crops. Successfully switching to a new host species requires multiple changes in a virus' genes, and there are many possible sets or pathways of change. Because these viruses are not pathogenic to humans, middle-school students at an urban charter school can be involved in some of the actual experimental work during an after-school activity. This research will be furthered by a laboratory course in experimental evolution for undergraduate students, and trainees supported by the grant will be mentored and trained in teaching techniques and curriculum development as well as research methods. Through this approach, 50 New Brunswick middle school students and 40 Rutgers undergraduates will be introduced to research in viral evolution, while two junior scientists will be prepared for an academic career that combines research and teaching.

The double-stranded RNA bacteriophage phi6, which infects different strains and species of Pseudomonas bacteria, will be used to study how initial host range mutations and previous evolution (mutations fixed during specialization on one host) affects phage evolutionary pathways and emergence in different novel hosts. Experimental evolution of replicate populations will expose phages to single or multiple hosts for over 100 generations at a time. Sequencing will determine how often the same mutations were fixed by replicate lineages, or by different genotypes. Finally, genetic crosses will create hybrid viral genotypes that will explore how interactions between mutations affect emergence on alternate strains of bacteria, and how many mutations trap a lineage by limiting its evolvability. These experiments will demonstrate how often RNA viruses must reverse substitutions that were adaptive in one environment in order to adapt to another.