Marine sponges and their associated symbionts produce a structurally diverse and complex set of natural products including alkaloids, terpenoids, peptides, lipids, and steroids. A single sponge with its symbionts can produce all of the above-mentioned classes of molecules and their analogs. Most approaches to evaluating sponge chemical diversity have focused on major metabolites that can be isolated and characterized; therefore, a comprehensive evaluation of intra- (within a molecular family; analogs) and inter-chemical diversity within a single sponge remains incomplete. We use a combination of metabolomics tools, including a supervised approach via manual library search and literature search, and an unsupervised approach via molecular networking and MS2LDA analysis to describe the intra and inter-chemical diversity present in Smenospongia aurea. Furthermore, we use imaging mass spectrometry to link this chemical diversity to either the sponge or the associated cyanobacteria. Using these approaches, we identify seven more molecular features that represent analogs of four previously known peptide/polyketide smenamides and assign the biosynthesis of these molecules to the symbiotic cyanobacteria by imaging mass spectrometry. We extend this analysis to a wide diversity of molecular classes including indole alkaloids and meroterpenes.
Keywords: Chemical diversity; Imaging mass spectrometry; MS2LDA; Marine sponge; Molecular networking; Untargeted metabolomics.