Date of Graduation


Document Type


Degree Type



Eberly College of Arts and Sciences



Committee Chair

Rita Rio

Committee Member

Geoffrey Attardo

Committee Member

Timothy Driscoll

Committee Member

Jennifer Gallagher

Committee Member

Teiya Kijimoto


Symbiosis is a long-term physical association between two or more species, although little is known regarding its evolutionary origins, particularly at the genetic level. Tsetse flies are the vector of African trypanosomes, causative agents of Human and Animal African Trypanosomiases. Tsetse provide an ideal model for studying initial and advanced stages of symbiosis. Tsetse have a simple digestive tract microbiota primarily consisting of two bacteria; the ancient mutualist Wigglesworthia glossinidia and the recently acquired Sodalis glossinidius. This work presents a chronological study in evolutionary terms of the history of a microbial-insect association. First, I present concepts on symbiosis and comments on tsetse and their native microbiota. Second, I focus on early evolutionary transition of an environmental bacterium to a symbiotic lifestyle. I show that quorum sensing virulence suppression facilitates the establishment of Sodalis-allied symbionts in diverse insects. Third, I compare the metatranscriptome of teneral Glossina morsitans (high vector competence) to that of Glossina brevipalpis (low vector competence). The transcriptomes of Wigglesworthia and Sodalis reflect differences in the extent of co-evolution with tsetse and identify pathways that may contribute towards distinctions in vector competence. Fourth, I present a theoretical mechanism by which microbial symbionts may control gene expression in insect host via epigenetics. I propose a link between the folate provisioning roles of the microbiota and the health of blood-feeding insects, via DNA methylation. This work reflects the use of a combined approach to gain a comprehensive understanding of symbiosis evolution, its mechanisms and its potential to impact epidemiology.

Embargo Reason

Publication Pending