NSF Postdoctoral Fellowship in Biology FY 2021: Evolution of bacterial strategies for evading predation by amoebae

Steele, Margaret I, St. Louis MO

Investigators

Abstract

This action funds an NSF Postdoctoral Research Fellowship in Biology for FY 2021, Integrative Research Investigating the Rules of Life Governing Interactions Between Genomes, Environment and Phenotypes. The fellowship supports research and training of the fellow that will contribute to the area of Rules of Life in innovative ways. The amoeba (called Dictyostelium discoideum) is a single-celled protist that lives in the soil, eats bacteria, and sometimes serves as a host to some bacteria. Though D. discoideum has served as a laboratory model for decades, relatively little is known about how its interactions with bacteria in the wild affect bacterial evolution. To date, few of the genes and molecular interactions that allow bacteria to escape predators or infect and exploit their would-be predator have been identified. The objective of this study is to explore the mechanisms bacteria use to interact with D. discoideum and test the hypothesis that distantly related bacteria have developed similar strategies. This will provide insight into the role of predation in driving the evolution of complex bacterial traits, such as the ability to evade predation, or manipulate host behavior. In addition to experimental work, this project will increase public participation in science by engaging undergraduate students in research and will inspire games and activities aimed at communicating the process of scientific discovery to the general public. This research investigates interactions between D. discoideum and 20 different bacteria. Effects of amoeba-bacteria interactions on the fitness of both participants will be quantified to categorize bacteria as beneficial prey, harmful pathogens, or predation-resistant but non-harmful symbionts. Transcriptomics will be used to evaluate the response of D. discoideum to each bacterium to determine whether distantly related bacteria in the same category achieve similar outcomes by targeting the same host pathways. Additionally, the rate at which D. discoideum ingests different bacteria and the duration of bacterial survival after ingestion will be measured through microscopy. Gene expression will be measured and manipulated to determine whether bacteria overcome host defenses by stimulating D. discoideum to overproduce the protein discoidin, which binds to cell membranes and increases bacterial survival after phagocytosis. Finally, comparative genomics will be used to look for bacterial genes that contribute to escape from predation. Findings from this study will help to bridge the gap between the present understanding of D. discoideum as a laboratory model and its role in natural microbial ecosystems. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.