Abstract: Sponges underpin the productivity of coral reefs, yet few of their microbial symbionts have been functionally characterized. Here we present an analysis of ~1200 metagenome-assembled genomes (MAGs) spanning seven sponge species and 25 microbial phyla. Addition of these MAGs to genome trees containing all sponge symbionts increased phylogenetic diversity by 44 and 75% for Bacteria and Archaea, respectively. Compared to MAGs derived from reef seawater, sponge-associated MAGs were enriched in glycosyl hydrolases targeting components of sponge tissue, coral mucus, and macroalgae, revealing a critical role for sponge symbionts in cycling reef organic matter. Genes for utilization of sponge glycans, like fibronectins and cadherins, were co-located in symbiont lineages capable of attaching to host surface proteins. Further, genes encoding CRISPR and restriction modification systems used in defence against mobile genetic elements were also enriched in sponge symbionts, along with multiple eukaryote-like gene motifs thought to be involved in maintaining host association. Finally, we provide evidence that many of these sponge-enriched genes are laterally transferred between microbial taxa, suggesting they confer a selective advantage within the sponge niche and therefore play a critical role in host ecology and evolution.

Biography: Steven Robbins is a native Ohioan who moved to Brisbane in 2011 to obtain his PhD at UQ. There, he investigated the metabolic pathways used to generate coal seam gas (CSG) and the effects of hydrofracture stimulation on CSG microbial communities. His postdoctoral work with the Great Barrier Reef Foundation’s ReFuGe2020 Consortium involved the integration of genomic data for several species of coral, as well as their Symbiodiniaceae and prokaryotic communities in order to clarify their individual roles within the coral holobiont. In his current role with Nicole Webster at the Australian Centre for Ecogenomics, he leverages large datasets of microbial genomes from marine sponges to identify the mechanisms underpinning sponge-microbe symbiosis.