Tracking the signaling cargo of extracellular symbionts into host tissues

Animal-microbe symbioses are fundamental to animal physiology but how and where bacteria interact with their host, remain largely elusive. The mutualistic association between the Hawaiian bobtail squid, Euprymna scolopes and its luminous bacterium Vibrio fischeri is a powerful model to investigate signaling between the host and its microbial symbiont. In this system, bacteria are acquired via horizontal transmission within hours of hatching and colonize the light organ as an extracellular partnership. Here, we combined TEM and NanoSIMS imaging to visualize 15N-labeled bacterial products within the tissue of newly-hatched squids. The nuclei of epithelial cells in the light organ were highly enriched in 15N with hotspots localized in the nucleolus as early as 2 h following inoculation. Closer examination revealed labeling was concentrated in the euchromatin regions of the nucleus, where DNA is often under active transcription. Taken together, our results show that V. fischeri-derived molecules target the host nucleus. We also exposed squid to 15N-labeled outer membrane vesicles (OMVs) extracted from V. fisheri as they are known to play a key role in signaling between symbiotic partners. Interestingly, 15N-enrichment patterns were similar to squid inoculated with intact bacteria. We are now exploring the species-specificity of these labeling patterns using other bacterial species. The unique link between spatial and functional information provided by the NanoSIMS technology has the potential to open a new frontier for the study of communication between host and symbiont.

Presented at:
13th International Coral Reef Symposium (ICRS 2016), Honolulu, Hawaii, 19-24 June

 Record created 2016-10-20, last modified 2018-09-13

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