Targeted Metagenomics: Finding Rare Tryptophan Dimer Natural Products in the Environment

Natural product discovery from environmental genomes (metagenornics) has largely been limited to the screening, of existing,environmental DNA (eDNA) libraries: Here, we have coupled a chemical-biogeographic survey of chroinopyrrolic acid synthase (CPAS) gene diversity with targeted eDNA. library production to more efficiently access,rare tryptophan dinner (TD) biosynthetic gene clusters. A combination of :traditional and,synthetic biology-bed heterologous expression efforts using,eDNA derived gene clusters led to the production of hydroxysporine (1)and reductasporine (2), two bioactive TDs. As suggested by but phylogeneic analysis of CPAS genes, identified in our survey of dude eDNA. extracts, reductasporine (2) contains an unprecedented TD core structure: a pyrrolinium indolocarbazole core that is likely key to its unusual bioactivity profile. This work demonstrates the potential for the discovery Of structurally rare and biologically interesting,natural products using targeted metagenomics, Where environmental samples are prescreened to identify the most phylogenetically unique gene sequences and molecules associated with these genes are accessed through targeted metagenomic library construction and heterologous expression.