DISSERTATION RESEARCH: Competition and cooperation in the honey bee gut microbiota

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Pollinator health is important for both agricultural and natural ecosystems, and one of the most important pollinators, especially in agriculture, is the honey bee. In this project, researchers will focus on bacteria in honey bee guts, because gut bacteria affect animals' health. They will study how these bacteria interact with one another, because this is important for how stable helpful gut bacterial communities are, and how they interact with the host animal. The researchers will continue working with two critical bacteria in the bee gut. They have already shown how these bacteria have toxins with which they can attack one another. However, it is likely that these bacteria also help one another in some situations. The researchers will use recently developed methods to look at whether and how these bacteria pass nutrients to one another and to the host bee. This will contribute to understanding how bee-gut bacterial communities stay stable through time. It will help to develop new routes to improving bee health. In addition, during the project graduate and undergraduate researchers will be trained in state-of-the-art methods in microbiology.As insects can take up and utilize byproducts of carbohydrate fermentation, honeybees may benefit from the metabolic activities of members of their gut microbial communities through both the degradation of toxic sugars and the production of useful byproducts. To better understand the role of cooperative metabolic interactions in gut communities, this project will trace nutrient exchange in the honeybee gut. Genomic evidence suggests that the bee gut microbes Snodgrassella alvi and Gilliamella apicola depend upon one another for production of nutrients. G. apicola metabolizes carbohydrates that S. alvi cannot, and metabolizes sugars found in nectar that are toxic to honey bees. This project will use isotopically-labeled monosaccharides that can be utilized by G. apicola, but not by S. alvi or the host, to trace metabolic interactions in the bee gut. DNA-stable isotope probing (DNA-SIP) will be used to track incorporation of labeled carbon atoms into bacterial DNA, while incorporation of these atoms into host tissues will be measured through elemental analysis and isotope ratio mass spectrometry. This research will contribute to a greater fundamental understanding of the processes that govern cooperative metabolic interactions among members of the gut microbiota and between the microbiota and the host, and will demonstrate the important potential role of SIP methods in hypothesis testing in microbial community ecology, a framework in which it is uncommonly used.