Interactions between calanoid copepod hosts and their associated microbiota

Abstract

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.