Evolutionary trade-offs between pesticide- and phage-resistance in a crop pathogen
Britt Koskella, Professor
Integrative Biology
Closed. This professor is continuing with Fall 2024 apprentices on this project; no new apprentices needed for Spring 2025.
Phage, viruses that infect and kill bacteria, are ubiquitous, yet their impacts on beneficial bacteria that colonize plants are not well understood. Phage are abundant in the soil and therefore soil-dwelling bacteria must hone defenses against phage in order to survive. Likewise, phage must hone their capacity to infect local bacteria in order to persist and multiply. On one hand, phage may adapt to be especially good at infecting local bacteria that co-occur with them, as the ability to infect local bacteria would allow them to thrive. On the other hand, bacteria could also adapt to be especially good at resisting infection by local phage that co-occur with them if only bacteria resistant to local phage can thrive at a site. We will test how these phage-bacterium dynamics play out over soils sampled from multiple sites from across California.
We will perform experiments to test how phage impact beneficial microbiome communities of rhizobium bacteria that colonize plants. Rhizobium bacteria are beneficial microbes that convert atmospheric nitrogen into a form that benefits plants in the pea family, essentially fertilizing them. We will generate a snapshot of bacteria-phage dynamics across California for a geographically widespread beneficial interaction between nitrogen-fixing Mesorhizobium rhizobium bacteria and a native California legume species. We will determine the phage network of infectivity across a panel of 315 Mesorhizobium strains using a high throughput liquid rhizobium culture technique. Phage will be isolated from Mesorhizobium exposed to the local phage community in soil samples. We will test one phage from each of 10 populations for its ability to infect the 315 Mesorhizobium strains collected from local and more distant populations.
Role: The undergraduate researcher will collaborate with visiting scholar, Associate Professor Stephanie Porter, to contribute to running infectivity tests by combining rhizobium bacteria strains with phage samples from soils in assays in the laboratory. They may also assist in developing methods to score and analyze optical density measurements from high throughput infectivity assays run on automated incubation instruments. The student will work directly with Dr. Porter and is encouraged to join weekly Koskella lab group meetings as well.
Qualifications: Students with strong interests in microbiology, virology, and evolutionary biology will find the experience most rewarding. Attention to detail, careful record keeping, and an interest in growing bacteria and phage are essential. Students with experience in microbiology and statistics or other research-related skills should note that in their application.
Day-to-day supervisor for this project: Stephanie Porter and Britt Koskella, Ph.D. candidate
Hours: 6-8 hrs
Biological & Health Sciences