Using magnetic nanoparticles to explore symbiotic interactions

All plants and animals form symbiotic associations with microbes, yet many of the underlying mechanisms associated with these interactions remain uncharacterized. There are inherent challenges to studying the cellular and metabolic interactions between eukaryotes and their microbial symbionts, thus new methodologies that enable the discovery of symbiotic processes are continually needed. Here, we explored the use of magnetic nanoparticles (MNPs) as a tool to track aspects of the host innate immune response to symbionts under both ex vivo and in vivo conditions. The symbiotic association between the Hawaiian bobtail squid Euprymna scolopes and its bioluminescent partner Vibrio fischeri was used as a model to explore the potential of MNPs as non-toxic, manipulable agents to investigate aquatic symbiotic associations. Results suggest that host cells can be effectively labeled with MNPs under ex vivo conditions and that the particles can be visualized and tracked within the host animal in vivo using magnetic particle imaging. Proteomic and metabolomic analyses also revealed minimal changes to the host innate immune cells after uptake of MNPs in the presence and absence of V. fischeri. Together, these results suggest that MNPs have minimal biochemical impact on the host cells and can serve as an effective tool to explore aquatic symbiotic interactions.