Project Summary The objective of this proposal is to create general, high-throughput assays that are modular and broad in scope to overcome the current bottleneck in testing the enormous diversity required for solving metabolic engineering problems. If successful, these technologies will enable powerful directed evolution approaches to be routinely applied to the biosynthesis of natural products and their analogs. Metabolic engineering involves library sizes of up to 1020, many orders of magnitude beyond now routine protein engineering, because multiple genes not only in the biosynthetic pathway but also in the host strain background must be optimized often synergistically. Yet, today metabolic engineering is primarily performed by introducing just a few genetic modifications at a time and then assaying the resulting strains by low throughput gas- and liquid-chromatography mass spectrometry methods. Previous high-throughput assays employed in metabolic engineering have been limited to unusual molecules, such as chromophores. Thus, here we apply the concept of displacement of a competitor molecule from a protein receptor to develop two general assays for metabolic engineering: the fluorescence polarization (FP) assay and the yeast three-hybrid (Y3H) selection. The FP assay would be implemented as a first-generation, medium throughput screen, as a step stone to the Y3H which would have higher throughput of greater than 108. When carried out under the conditions of sexual reproduction with mutagenesis via homologous recombination (HR), libraries of greater than 1020 can be searched. In collaboration with the Tang laboratory (UCLA) and the Snyder laboratory (UChicago), we challenge our technology with the metabolic engineering mission of increasing production titers of the fungal anhydrotetracycline TAN-1612 and generating biologically active analogs in S. cerevisiae for combating antibiotic resistance and applications beyond.