UC San Diego

Nature has created elegant and efficient ways of assembling a wide variety of diverse chemical scaffolds. Microbes are prolific producers of these secondary metabolites, which can have profound bioactivities and be harnessed for use in medicine. Within their genomes, microbes possess the blueprints for making natural products, and recent advances in high-throughput DNA sequencing have revealed a much larger repertoire of specialized chemistry than what can be observed in the lab. This bacterial ‘dark matter’ has the potential to contain the instructions for making countless new chemical scaffolds and represents an untapped source for drug discovery. Connecting secondary metabolite compounds with their biosynthetic gene clusters can inform novel biosynthetic transformations, provide a renewable source of promising bioactive compounds, and inspire synthetic biology approaches to assembling new molecules. Chapter 2 of this dissertation connects two pharmaceutically relevant natural products with their corresponding biosynthetic gene clusters. The epoxyketone proteasome inhibitors epoxomicin and eponemycin are naturally produced by actinomycete bacteria, and whole genome sequencing revealed their genetic underpinnings and native resistance mechanism. This work represents the first elucidation of biosynthetic gene clusters for epoxyketone proteasome inhibitors. Chapter 3 takes a wider lens to examine an understudied group of bacteria: the rare marine actinomycetes. Whole genome sequencing of a group of rare marine actinomycetes revealed an incredible wealth of biosynthetic potential and diversity not yet represented in current sequencing databases. This study establishes rare marine actinomycetes as a group worthy of further exploration for genome mining and drug discovery. Chapter 4 investigates a more complex system with a focus on uncultivatable cyanobacterial sponge symbionts. Previous work showed that the genomes of these symbionts contained the genes necessary to produce environmentally relevant poly-brominated diphenyl ethers (PBDEs). In assembling high quality draft genomes of two symbionts of distinct sponges, their full secondary metabolite potential was revealed. Additionally, genome mining led to the identification of two novel dysinosin molecules, representing the first example of mining for gene clusters in a metagenome assembled genome leading to new chemistry.