Dissecting the microbiome of a polyketide-producing ascidian across the Anvers Island archipelago, Antarctica

The regional survey of palmerolide A (PalA) levels and host-associated microbiome composition in the Antarctic ascidian, Synoicum adareanum, provides an essential step along the path to discovering the PalA producing microorganism. Uniform, high levels of PalA were present across all S. adareanum multi-lobed colonies sampled in the Anvers Island archipelago. Likewise, we identified a coresuite of microorganisms, distinct from the picoplankton, that occur concurrently with the PalA-containing ascidians which spanned four phyla with lineages representing both heterotrophic and chemoautotrophic (ammonia oxidizing) metabolisms, that are leads for PalA production. Cultivation efforts did not yield a palmerolide-producing organism as of yet, though one of the isolates, Pseudovibrio sp. TunPSC04-5.I4, was represented in the core at high relative abundance. Bioinformatic analysis of biosynthetic gene clusters in the PSC04-5I4 genome did not support the predicted machinery for palmerolide biosynthesis.