Bacteria associated with the in hospite Symbiodiniaceae's phycosphere.

Symbiotic interactions between Symbiodiniaceae and bacteria are still poorly explored, especially those in hospite . Here, we adapted a technique that allows for the enrichment of intact and metabolically active in hospite Symbiodiniaceae cells ( ih SC) and their associated bacteria from the tissue of the model coral Pocillopora damicornis , using a discontinuous gradient of solution of isotonic Percoll (SIP). The ih SC were concentrated in the 50% SIP fraction, as determined by microscopy. The presence of bacteria associated with ih SC was confirmed by fluorescence in situ hybridization, while microbiome analysis indicated that bacteria of the families Halieaceae , Flavobacteriaceae , and Alcanivoraceae are significantly associated with ih SC. Extracellular vesicles that could be exuding molecules were detected on the symbiosome membranes. Our technique and data contribute to elucidate ih SC-bacteria interactions.