Discovery and biosynthetic assessment ofStreptomyces ortussp nov. isolated from a deep-sea sponge

AbstractThe deep sea is known to host novel bacteria with the potential to produce a diverse array of undiscovered natural products. Understanding these bacteria is thus of broad interest in ecology and could also underpin applied drug discovery, specifically in the area of antimicrobials. Here, we isolate a new strain ofStreptomycesfrom the tissue of the deep-sea spongePolymastia corticatacollected at a depth of 1869 m from the Gramberg seamount in the Atlantic Ocean. This strain, which was given the initial designation A15ISP2-DRY2T, has a genome size of 9.29 Mb with a GC content of 70.83%. Phylogenomics determined that A15ISP2-DRY2Trepresents a novel species within the genusStreptomycesas part of theStreptomyces aurantiacusclade. The biosynthetic potential of A15ISP2-DRY2Twas assessed relative to other members of theaurantiacusclade via comparative gene cluster family (GCF) analysis. This revealed a clear congruent relationship between phylogeny and GCF content. A15ISP2-DRY2Tcontains six unique GCFs absent elsewhere in the clade. Culture-based assays were used to demonstrate the antibacterial activity of A15ISP2-DRY2Tagainst two drug-resistant human pathogens. We thus determine A15ISP2-DRY2Tto be a novel bacterial species with considerable biosynthetic potential and propose the systematic nameStreptomyces ortussp. nov.Impact StatementTheStreptomycesgenus has contributed more to our antibiotic arsenal than any other group of bacteria or fungi. Despite decades of exploration, global analysis has suggested they still possess more undiscovered biosynthetic diversity than any other bacterial group. Isolating novel species ofStreptomycesis therefore a priority for antibiotic discovery. Here we isolate a novel strain from a deep-sea sponge and use comparative cluster analysis to identify six biosynthetic clusters unique to our deep-sea strain. This work demonstrates the utility of continuing to isolate novelStreptomycesstrains for antibiotic discovery and, for the first time, we used species tree-gene cluster tree reconciliation to assess the contribution of vertical evolution on the biosynthetic gene cluster content ofStreptomyces.