Trait-Based Comparison of Coral and Sponge Microbiomes

Abstract

corals and sponges harbor diverse microbial communities that are integral to the functioning of the host. While the taxonomic diversity of their microbiomes has been well-established for corals and sponges, their functional roles are less well-understood. It is unclear if the similarities of symbiosis in an invertebrate host would result in functionally similar microbiomes, or if differences in host phylogeny and environmentally driven microhabitats within each host would shape functionally distinct communities. Here we addressed this question, using metatranscriptomic and 16S rRNA gene profiling techniques to compare the microbiomes of two host organisms from different phyla. Our results indicate functional similarity in carbon, nitrogen, and sulfur assimilation, and aerobic nitrogen cycling. Additionally, there were few statistical differences in pathway coverage or abundance between the two hosts. For example, we observed higher coverage of phosphonate and siderophore metabolic pathways in the star coral, Montastraea cavernosa, while there was higher coverage of chloroalkane metabolism in the giant barrel sponge, Xestospongia muta. Higher abundance of genes associated with carbon fixation pathways was also observed in M. cavernosa, while in X. muta there was higher abundance of fatty acid metabolic pathways. Metagenomic predictions based on 16S rRNA gene profiling analysis were similar, and there was high correlation between the metatranscriptome and metagenome predictions for both hosts. our results highlight several metabolic pathways that exhibit functional similarity in these coral and sponge microbiomes despite the taxonomic differences between the two microbiomes, as well as potential specialization of some microbially based metabolism within each host. Microbial symbionts have played a critical role in shaping the evolution of multicellular life by facilitating and promoting host defense 1 , nutrient acquisition 2 , and species diversification 3. For example, in coral reef ecosystems, intracellular dinoflagellates in the Family Symbiodiniaceae occur as the primary mutualistic symbionts within the coral host and are essential to the survival and growth of the coral host, while receiving a suitable habitat and essential nutrients in return 4,5. Prokaryotic symbionts also contribute to the success of coral reef organisms, including corals and sponges 6-9 , by providing bioactive compounds for chemical defenses 10,11 , recycling host waste 12,13 , and in some cases providing a reliable source of vitamins and nutrients 14-17. Numerous studies have characterized the taxonomic composition of microbes in corals and sponges 18,19 ; however, our understanding of the multiple functional roles of these symbionts is still incomplete. Corals and sponges harbor remarkably diverse prokaryotic symbionts with thousands of unique taxa in many coral and sponge species 20,21. Many of these taxa persist across different host species (i.e., the core microbiome) over broad spatial scales 9,22-24 , and in some cases these host-...

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Circadian dynamics of the teleost skin immune-microbiome interface

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