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Dissertation/Thesis Abstract

Microbe-microbe interactions in the Drosophila melanogaster microbiome
by Fischer, Caleb Nathaniel, Ph.D., Yale University, 2016, 211; 10584945
Abstract (Summary)

Microbiologists have traditionally focused on understanding the lethal consequences instigated by a handful of microorganisms. Nonetheless, the symbiotic nature of microorganisms was evident at the dawn of microbiology when Anton Van Leeuwenhoek discovered thousands of microorganisms inside the human oral cavity. Over the last century, the realization that microorganisms benefit animals has eroded the ossified perspective that microorganisms are primarily harmful. Instead, microorganisms are regarded as fundamental to animal biology.

A central goal in microbiology is to understand the molecular mechanisms by which symbiotic microorganisms associate with their hosts. The mechanisms underpinning microbial community function depend on a complex suite of metabolic interactions between microorganisms. In this dissertation, the model system Drosophila melanogaster and its simple microbiome will be used to deconstruct the mechanisms underlying microbe-microbe interactions and their consequences on host biology.

CHAPTER 1: Greater than the sum of the parts: microbe-microbe interactions in gut microbiomes. In this introductory chapter, progress in understanding microbe-microbe interactions in host-associated microbial communities will be discussed. This chapter will organize attempts at understanding microbe-microbe interactions within hosts into top-down and bottom-up approaches. The two approaches are complementary and rest on starting with pairwise interactions (bottom-up) versus modeling all interactions (top-down). Drosophila melanogaster is an attractive model system in which both approaches can be used due to the simplicity of its microbiome.

CHAPTER 2: Frequent replenishment sustains the beneficial microbiome of Drosophila melanogaster. The characterization of several ecological properties of the Drosophila microbiome, including its assembly and maintenance, will be discussed. The study also sheds light on a microbe-microbe interaction and its consequence for host infectious disease.

CHAPTER 3: Metabolite exchange within the microbiome produces compounds that influence Drosophila behavior. Drosophila olfactory behavior toward microbiome members, individually and in communities, will be assessed. The work presented in this chapter supports a model whereby Drosophila identifies interacting microbial communities via their production of specific metabolites. The molecular differences by which Drosophila discriminates a co-culture from the same two microorganisms growing separately are identified. The behavior corresponds with Drosophila egg-laying preference and adult survival. The results are discussed in light of the potential role of the observed behavior in microbiome assembly and maintenance.

CHAPTER 4: Conclusions and future directions. In this chapter the major findings of the dissertation will be placed into context of their potential ecological significance. Future research questions that emanate from the findings of the dissertation will be discussed. APPENDIX I: Microbe-microbe interactions and their impact on Drosophila egg-laying behavior.

APPENDIX I: Microbe-microbe interactions and their impact on Drosophila egg-laying behavior.Appendix I identifies in vitro microbe-microbe interactions between Drosophila microbiome members and their consequence for Drosophila egg-laying behavior.

APPENDIX II: Invasion of the Drosophila gut microbiome by human fecal bacteria. Results that characterized the Drosophila microbiome following invasion from a single microorganism (Enterococcus faecalis) and a complex community (fecal microbiome) are discussed.

APPENDIX III: Drosophila feeding behavior toward microbiome members. The adaptation of the capillary feeding (CAFE) to interrogate Drosophila behavior toward microbiome members will be discussed.

APPENDIX IV: Costs of the Drosophila bacterial microbiome. Consumption and survival costs of the bacterial microbiome in Drosophila will be highlighted.

Indexing (document details)
Advisor: Handelsman, Jo
School: Yale University
School Location: United States -- Connecticut
Source: DAI-B 78/07(E), Dissertation Abstracts International
Subjects: Ecology, Microbiology, Analytical chemistry
Keywords: Behavior, Drosophila Melanogaster, Metabolites, Microbiome, Microbiome Stability
Publication Number: 10584945
ISBN: 978-1-369-63533-1
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