| Summary: | Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution February 2015 Copepods are highly abundant environmental reservoirs of many bacterial pathogens. This thesis investigates whether copepod physiology influences the abundance and community structure of its microbiome. To this end, we first examined the ability of the oceanic copepod Calanus finmarchicus to transcriptionally respond to mild stressors and demonstrated that heat shock proteins (Hsps) are a conserved element of the copepod’s regulation of stressful conditions and diapause. We then investigated the transcriptomic response of an estuarine copepod Eurytemora affinis to two distinct Vibrio species, a free-living (V. ordalii 12B09) and a zooplankton specialist (V. sp. F10 9ZB36), and found that E. affinis distinctly responds to colonizing Vibrios. Finally, we probed how specifically and predictably bacterial communities assemble on C. finmarchicus. Our findings suggest that C. finmarchicus has a predictable “core microbiome” that persists throughout the host’s entrance into diapause. Furthermore, the structure of the copepod microbiome may be driven by a combination of the copepod’s feeding history, body size, and bacterial interactions. This thesis work highlights the role of copepods as dynamic reservoirs of diverse microbial communities and implicates copepod host physiology as an important contributor to the activity, abundance, and community structure of its often pathogenic microbiota. This work has been supported by a National Science Foundation Graduate Research Fellowship, an Environmental Protection Agency Science to Achieve Results Fellowship, National Science Foundation Grants (OCE-1132567 to AM Tarrant and MF Baumgartner), student awards from the WHOI Ocean Venture Fund, and private donation from Richard and Susan Hill.
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