Coral reefs cover less than 1 per cent of the ocean floor yet host over a third of marine animal and plant species, and their microbial inhabitants have remained almost entirely uncharted. ETH Zurich groups led by Shinichi Sunagawa and Jörn Piel, with collaborators at EPFL and the Tara Pacific Consortium, analysed more than 800 coral samples collected during the Tara Pacific Expedition of 2016 to 2018. The study appears in Nature.
Using high-performance computing at ETH to piece together sequenced DNA fragments, the team reconstructed the genomes of 645 bacterial and archaeal species, over 99 per cent of which had no previously available genomic information. The microbes proved largely specific to particular coral genera and confined to the reefs rather than spread through the open Pacific, and their genomes encode more potential for natural products than the researchers had previously found across the entire open ocean.
Such compounds, likely chemical defences honed in the crowded conditions of a reef, could seed future medicines and biotechnology. The survey covered just three coral genera out of several hundred, hinting at vast unexplored diversity in corals, sponges, molluscs and algae. With half the world's coral population lost since the 1950s, the authors argue that conservation should protect not only the corals but the invisible pharmacy living within them.