Abstract
Marine sponges are ancient metazoans that are populated by distinct and highly diverse microbial communities. In order to obtain deeper insights into the functional gene repertoire of the Mediterranean sponge Aplysina aerophoba, we combined Illumina short-read and PacBio long-read sequencing followed by un-targeted metagenomic binning. We identified a total of 37 high-quality bins representing 11 bacterial phyla and two candidate phyla. Statistical comparison of symbiont genomes with selected reference genomes revealed a significant enrichment of genes related to bacterial defense (restriction-modification systems, toxin-antitoxin systems) as well as genes involved in host colonization and extracellular matrix utilization in sponge symbionts. A within-symbionts genome comparison revealed a nutritional specialization of at least two symbiont guilds, where one appears to metabolize carnitine and the other sulfated polysaccharides, both of which are abundant molecules in the sponge extracellular matrix. A third guild of symbionts may be viewed as nutritional generalists that perform largely the same metabolic pathways but lack such extraordinary numbers of the relevant genes. This study characterizes the genomic repertoire of sponge symbionts at an unprecedented resolution and it provides greater insights into the molecular mechanisms underlying microbial-sponge symbiosis.
Highlights
Marine sponges (Porifera) are evolutionary ancient metazoans dating back to Precambrian times (Li et al, 1998; Love et al, 2009)
By filtering extensive volumes of seawater—up to thousands of liters per kg sponge daily (Reiswig, 1974)—they take in food bacteria, and potential pathogens, toxins and physical stress factors (De Goeij et al, 2009)
Rapid cell turnover rates accompanied by extensive detritus production are likely a means of avoiding permanent, stress-induced damage to the sponge (De Goeij et al, 2009; Alexander et al, 2014)
Summary
Marine sponges (Porifera) are evolutionary ancient metazoans dating back to Precambrian times (Li et al, 1998; Love et al, 2009). In order to obtain deeper insights into the functional gene repertoire of the Mediterranean sponge Aplysina aerophoba, we combined Illumina short-read and PacBio long-read sequencing followed by un-targeted metagenomic binning.
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