# New insights into the microbiome of the deep-sea sponge Inflatella pellicula and the secondary metabolic potential of metagenome-assembled genomes and the wider microbiome

## TL;DR

This study explores the microbiome of a deep-sea sponge and finds unique genetic potential for producing new chemical compounds.

## Contribution

The study reveals the unique secondary metabolic potential of the deep-sea sponge Inflatella pellicula's microbiome.

## Key findings

- A large fraction of the sponge's metagenome could not be taxonomically classified, indicating 'biological dark matter'.
- Few metagenome-assembled genomes and secondary metabolism gene clusters were identified, but they were distinct from known clusters.
- Some gene clusters showed similarities to those from sponges in other geographic regions, suggesting shared biosynthetic potential.

## Abstract

Marine sponges are found in all of the world’s oceans, from the surface waters to the deepest abyssal zones. The marine sponge holobiont is a rich source of microbial and chemical diversity. Up to 63 bacterial phyla have been observed to be associated with sponges, and thousands of unique natural products have been extracted from sponges or their microbial symbionts. However, sponges from the deep sea and their associated microbial communities are relatively understudied, largely due to sampling-associated difficulties. Secondary metabolism biosynthetic gene clusters are phylogenetically distinct and hold the potential to produce novel chemistry with potential pharmacological or industrial utility. In order to gain further insights into the microbiome of the deep-sea sponge Inflatella pellicula, the metagenome of this sponge, sampled from a depth of 2,900 m, was sequenced. A large fraction of the sequence reads appeared to be ‘biological dark matter’ and could not be taxonomically classified. Further, unlike similar studies from different marine ecosystems, relatively few metagenome-assembled genomes (MAGs) could be assembled, and relatively few secondary metabolism biosynthetic gene clusters were identified. The identified clusters were, however, very dissimilar to known characterized clusters, but some shared similarities with clusters annotated in MAGs assembled from sponge metagenomes from disparate geographic locations. Therefore, renewed efforts to cultivate the hosts of these gene clusters may yield valuable small-molecule natural products.