Author's Department


Date Submitted


Research Mentor and Department

Joan Strassmann (Biology), David Queller (Biology), Debra Brock (Biology)




Some of the closest interactions between organisms can be found within symbioses, where different individuals live in close physiological contact and either benefit or harm the other. A powerful kind of benefit comes when bacterial symbionts produce amino acids or provide digestive capabilities outside the host’s ability, in essence taking advantage of the other’s genetic catalog. One such symbiosis is that of the social amoeba Dictyostelium discoideum and its bacterial symbionts Burkholderia agricolaris, Burkholderia hayleyella, and Burkholderia bonneia. In this symbiosis, Burkholderia provide the capability of carrying food bacteria to their host, an advantageous trait when bacterial food is rare. In this thesis, I explore whether or notBurkholderia is able to colonize multiple species of Dictyostelids and also investigate the mechanisms it uses. In Chapter 1, I exposed several Dictyostelids to three Burkholderia species isolated from D. discoideum to determine whether Burkholderia is a specific or generalist symbiont. In Chapter 2, I tried numerous DNA manipulation methods to knock out the genes inBurkholderia that allow it to enter a symbiotic relationship with D. discoideum. In Chapter 3, I describe ways in which I have benefited the larger community. Specifically, I created an outreach project on microbes used at the local Ferguson Farmer’s market and videos on microbial techniques for use with undergraduates and high school students. By understanding how and to what extent Burkholderia enters its symbiotic relationship with Dictyostelids, we can further our understanding of what general factors lead to the evolution of symbiotic relationships as a whole.