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Subterranean microbial communities possess unique and untapped biosynthetic potential. 

BackgroundBats, critical to controlling insect populations, harbor unique immune systems that can provide insight into preventing and treating diseases. Unfortunately, white-nose syndrome (WNS), caused by the fungusPseudogymnoascus destructans,has devastated North American bat populations, killing millions since the winter of 2006 in one of the greatest wildlife disease epidemics in U.S. history. Several reports have found evidence that bat microbiomes play a role in protecting their host against WNS. However, investigations into the antifungal metabolites produced by these symbionts are extremely limited. ObjectiveThe aim of this study was to investigate the antifungal constituents ofStreptomyces buecherae,a novel bat-associated bacterium isolated from bats in New Mexico. MethodsTo identify bioactive compounds from the complex bacterial extract, we combined untargeted mass spectrometry metabolomics within vitroantifungal activity data againstP. destructans, identifying a suite of antifungal metabolites for targeted study using biochemometric partial least squares analyses combined with molecular networking. ResultsThe metabolomics analyses revealed that nigericin—a known polyether antibiotic—was the major bioactive compound in the extract, and molecular networking revealed additional nigericin analogs present in the bioactive extract. Nigericin showed moderate antifungal activity againstP. destructansin a disc diffusion assay down to a concentration of 6.25 μg/disc. ConclusionsNigericin is the primary bioactive constituent present inS. buecheraeextracts that may be responsible for the antifungal effect this bacterium shows againstP. destructans in vitro.This study underscores the potential of bat-associatedStreptomycesspecies in combatting fungal pathogens and provides insight into the chemical mechanisms involved in bat microbiome defenses against WNS. 

Abstract IntroductionFungi biosynthesize chemically diverse secondary metabolites with a wide range of biological activities. Natural product scientists have increasingly turned towards bioinformatics approaches, combining metabolomics and genomics to target secondary metabolites and their biosynthetic machinery. We recently applied an integrated metabologenomics workflow to 110 fungi and identified more than 230 high-confidence linkages between metabolites and their biosynthetic pathways. ObjectivesTo prioritize the discovery of bioactive natural products and their biosynthetic pathways from these hundreds of high-confidence linkages, we developed a bioactivity-driven metabologenomics workflow combining quantitative chemical information, antiproliferative bioactivity data, and genome sequences. MethodsThe 110 fungi from our metabologenomics study were tested against multiple cancer cell lines to identify which strains produced antiproliferative natural products. Three strains were selected for further study, fractionated using flash chromatography, and subjected to an additional round of bioactivity testing and mass spectral analysis. Data were overlaid using biochemometrics analysis to predict active constituents early in the fractionation process following which their biosynthetic pathways were identified using metabologenomics. ResultsWe isolated three new-to-nature stemphone analogs, 19-acetylstemphones G (1), B (2) and E (3), that demonstrated antiproliferative activity ranging from 3 to 5 µM against human melanoma (MDA-MB-435) and ovarian cancer (OVACR3) cells. We proposed a rational biosynthetic pathway for these compounds, highlighting the potential of using bioactivity as a filter for the analysis of integrated—Omics datasets. ConclusionsThis work demonstrates how the incorporation of biochemometrics as a third dimension into the metabologenomics workflow can identify bioactive metabolites and link them to their biosynthetic machinery. 

Introduction Fungi biosynthesize chemically diverse secondary metabolites with a wide range of biological activities. Natu- ral product scientists have increasingly turned towards bioinformatics approaches, combining metabolomics and genomics to target secondary metabolites and their biosynthetic machinery. We recently applied an integrated metabologenomics workflow to 110 fungi and identified more than 230 high-confidence linkages between metabolites and their biosynthetic pathways. Objectives To prioritize the discovery of bioactive natural products and their biosynthetic pathways from these hundreds of high-confidence linkages, we developed a bioactivity-driven metabologenomics workflow combining quantitative chemical information, antiproliferative bioactivity data, and genome sequences. Methods The 110 fungi from our metabologenomics study were tested against multiple cancer cell lines to identify which strains produced antiproliferative natural products. Three strains were selected for further study, fractionated using flash chromatography, and subjected to an additional round of bioactivity testing and mass spectral analysis. Data were overlaid using biochemometrics analysis to predict active constituents early in the fractionation process following which their bio- synthetic pathways were identified using metabologenomics. Results We isolated three new-to-nature stemphone analogs, 19-acetylstemphones G (1), B (2) and E (3), that demonstrated antiproliferative activity ranging from 3 to 5 μM against human melanoma (MDA-MB-435) and ovarian cancer (OVACR3) cells. We proposed a rational biosynthetic pathway for these compounds, highlighting the potential of using bioactivity as a filter for the analysis of integrated—Omics datasets. Conclusions This work demonstrates how the incorporation of biochemometrics as a third dimension into the metabolog- enomics workflow can identify bioactive metabolites and link them to their biosynthetic machinery.