Project Summary / Abstract Natural products continue to provide important drug leads in medicine. While the majority of clinical antibiotics are derived from bacterial natural products, the emergence of antibiotic resistance emphasizes the need to discover new antimicrobial leads. This renewal application builds upon a productive collaboration between the Jensen (microbiology/bioinformatics) and Moore (biosynthesis/natural products chemistry) laboratories to address this need through the mining of microbial genomes and metagenomes for new bioactive compounds. We have prioritized two diverse groups of chemically gifted marine bacteria for study from a collection of >10,000 strains collected across the world’s oceans. We continue our efforts with the obligate marine actinomycete Salinispora, which produces the potent proteasome inhibitor salinosporamide A (Marizomib) that is presently in phase III trials to treat brain cancer. Here we capitalize on the recent identification of six new Salinispora species and 99 new genomes to expand our efforts in this unique taxon. We further expand our genome mining efforts to include the MAR4 lineage, a second chemically gifted group of marine bacteria for which we are uniquely situated to explore with 42 new genomes. This lineage shows the first evidence that marine adaptations are linked to natural product biosynthesis and includes at least six new species. We have identified hundreds of orphan biosynthetic gene clusters (BGCs) in these two groups and prioritized them as lead discovery targets. We have further taken this program into new directions by mining BGCs directly from environmental DNA (eDNA) using a nontargeted metagenomic approach that provides unbiased access to the biosynthetic potential of microbial diversity. These samples originate from both shallow tropical ocean sediments (1515 natural product BGCs already assembled) as well as deep sea sediments (down to 2000 meters) that are being collected for this program and have yet to be explored for natural products research. We will maximize access to these unique resources and employ innovative techniques in genome mining and synthetic biology to prioritize the targeted discovery of new antibiotic leads such as beta-lactone-containing products from eDNA that are predicted to inhibit protease virulence factors in Gram(-) bacteria. These genome mining efforts are governed by a logical workflow that prioritizes novel antibiotic discovery from poorly explored microbial resources.