Beyond the zooxanthellae, exploring the diversity of coral associated microeukaryotes

Microbiome Center

Javier del Campo, Ph.D., University of Miami

August 7, 2020 @ 11:00 am to 12:00 pm


Microbiomes associated with animals have a strong influence on host evolution, physiology and ecological functions. Unlike the study of bacterial microbiomes, the study of the microeukaryotes associated with animals has largely been limited to visual identification or molecular targeting of particular groups. The application of high-throughput sequencing (HTS) approaches, such as those used to look at bacteria, has been restricted because the barcoding gene we use to study microeukaryotic ecology and distribution in the environment, the 18S rRNA gene, is also present in the host animals. As a consequence, when animal-associated microbial eukaryotes are analyzed by HTS, the results are dominated by host sequences. Stemming from our work on marine animals associated micro-eukaryotes, we successfully developed an approach that avoids the amplification of metazoan host genes, which allows us to use high-throughput methods to study the microeukaryotic communities of animals. Among corals, the most well-known member of the holobiont, apart from the coral itself, is the zooxanthellae, which is indeed a microeukaryote. However, as we mentioned before, corals are not an exception and we know little about the rest of the microeukaryotes that are part of their microbiome. In recent years we have learned more about microeukaryotic members of the holobiont such as the green algae Ostreobium and the apicomplexan corallicollids, but there are many others that have been observed such as labyrinthulids, ciliates or fungi that we know little about and probably there are others that have never been reported. Using the aforementioned methods, we have explored the microeukaryotic diversity associated with zooxanthellate and azooxanthellate corals from warm and cold environments using HTS. Our data confirms the presence of some of the previously described holobiont microeukaryotes and also reveals the presence of others such as red algae or the parasitic syndiniales. As for the rest of the microbiome we observed that the eukaryome varies between coral families and also depends on the health status of the host. Our results contribute to a better and more comprehensive understanding of the holobiont and our methods will help to stablish the basis to fully incorporate microeukaryotes in coral microbiome studies.