Taxonomic and Functional Microbial Signatures of the Endemic Marine Sponge <em>Arenosclera brasiliensis</em>

<div><p>The endemic marine sponge <em>Arenosclera brasiliensis</em> (Porifera, Demospongiae, Haplosclerida) is a known source of secondary metabolites such as arenosclerins A-C. In the present study, we established the composition of the <em>A. brasiliensis</em> microbiome and the metabolic pathways associated with this community. We used 454 shotgun pyrosequencing to generate approximately 640,000 high-quality sponge-derived sequences (∼150 Mb). Clustering analysis including sponge, seawater and twenty-three other metagenomes derived from marine animal microbiomes shows that <em>A. brasiliensis</em> contains a specific microbiome. Fourteen bacterial phyla (including <em>Proteobacteria</em>, <em>Cyanobacteria</em>, <em>Actinobacteria</em>, <em>Bacteroidetes</em>, <em>Firmicutes</em> and <em>Cloroflexi</em>) were consistently found in the <em>A. brasiliensis</em> metagenomes. The <em>A. brasiliensis</em> microbiome is enriched for <em>Betaproteobacteria</em> (e.g., <em>Burkholderia</em>) and <em>Gammaproteobacteria</em> (e.g., <em>Pseudomonas</em> and <em>Alteromonas</em>) compared with the surrounding planktonic microbial communities. Functional analysis based on <b>R</b>apid <b>A</b>nnotation using <b>S</b>ubsystem <b>T</b>echnology (RAST) indicated that the <em>A. brasiliensis</em> microbiome is enriched for sequences associated with membrane transport and one-carbon metabolism. In addition, there was an overrepresentation of sequences associated with aerobic and anaerobic metabolism as well as the synthesis and degradation of secondary metabolites. This study represents the first analysis of sponge-associated microbial communities via shotgun pyrosequencing, a strategy commonly applied in similar analyses in other marine invertebrate hosts, such as corals and algae. We demonstrate that <em>A. brasiliensis</em> has a unique microbiome that is distinct from that of the surrounding planktonic microbes and from other marine organisms, indicating a species-specific microbiome.</p>