Composition and Assembly of the Drosophila Microbiome

• Main Author: Chandler, James Angus Feinstein Seidler
• Format: Dissertation
• Language: English
• Subjects: ecology; microbiology; parasitology
• ISBN: 9781303442278; 1303442272

The microbial communities of animals (collectively called the animal microbiota) play important roles in human health, the pest status of agricultural insects, and the evolutionary potential and diversification of animal lineages. Drosophila is a promising model for the study of the animal microbiota because this system combines ecological diversity with genetic and experimental tractability. However, in order to understand the role of microbes in Drosophila physiology, ecology, and evolution, we first need to characterize the diversity of the Drosophila microbiota and establish which factors, environmental or genetic, are most important in determining microbial community composition.
My work is the first to provide a culture-independent characterization of the bacterial and yeast communities associated with ecologically, phylogenetically, and geographically diverse Drosophila populations. I find that Drosophila-associated microbial communities are dominated by a small number of abundant taxa, that the same microbial lineages are associated with different host species and populations, and that host diet has a greater effect on community composition than host species or location. Furthermore, the same samples of flies were used for both the bacterial and the yeast community characterizations, allowing the opportunity to compare the structure of two microbial groups in the same hosts. I did not detect a significant correlation in community structure between these two symbiont groups indicating that while diet shapes the structure of both symbiont communities, other factors, such as bacteria- or yeast-specific immunity, may also be important. Finally, through a fortuitous error in primer selection, I discovered that over two-thirds of the sampled Drosophila populations were associated with trypanosomatid parasites. Given that trypanosomatids are responsible for several clinically important diseases and that Drosophila is the best developed system for studying the interactions between insects and pathogens, this work may lead to Drosophila becoming a model for investigating how the insect immune system interacts with these important, but often neglected, parasites. This comprehensive dissertation lays the foundation for future interdisciplinary research programs that will use Drosophila as a model for investigating fundamental topics in animal-microbe interactions.