Across eight sponge chemotypes, the study identifies 14 Entotheonella phylotypes and an additional Proxinella candidate genus, revealing extensive BGC diversity beyond earlier samples.

Sponges host rich bioactive natural products, many produced by their microbial communities, particularly uncultivated symbionts like Entotheonellaeota (Entotheonella).

Overall, Entotheonellaeota symbionts harbor broad and diverse chemical potential across multiple sponge hosts, underpinning opportunities for discovering natural products from microbial dark matter and underscoring ecological and biotechnological importance of uncultivated symbionts.

Entotheonella phylotypes harbor unusually large genomes (roughly 5.36 to 16.54 Mbp) with high biosynthetic potential, carrying 10 to 42 biosynthetic gene clusters per genome, including large multimodular PKS/NRPS pathways that could produce known sponge metabolites and many orphan natural products.

AntiSMASH and BiG-SCAPE analysis show that only a small fraction of BGCs map to known compounds; the vast majority (357 of 369 gene cluster families) remain unassigned, revealing a vast untapped resource for natural product discovery.

BGCs exhibit mobility and horizontal transfer, with some BGCs linked to known sponge metabolites on plasmids or shared across Entotheonella variants, indicating dynamic exchange and adaptation.

Several BGCs of interest include potential RiPPs and unusual NRPS clusters, with novel enzyme architectures such as dioxygenase-RiPP fusions and SelA/SelB-related elements suggesting noncanonical biosynthetic chemistry.

The study expands Entotheonella diversity by identifying a new sister genus, Proxinella (AC1), associated with BGC-rich genomes, broadening the tectomicrobial landscape.

Shared BGCs across phylotypes often relate to primary metabolism or conserved redox roles (hopanoids, carotenoids, ectoine, type III PKS-derived alkyl resorcinols), while many highly similar loci involve orphan or poorly characterized pathways.