TY - JOUR T1 - Establishing Probiotic <em>Saccharomyces boulardii</em> as a Model Organism for Synthesis and Delivery of Biomolecules JF - bioRxiv DO - 10.1101/2020.01.22.915389 SP - 2020.01.22.915389 AU - Deniz Durmusoglu AU - Ibrahim Al’Abri AU - Scott P. Collins AU - Chase Beisel AU - Nathan Crook Y1 - 2020/01/01 UR - http://biorxiv.org/content/early/2020/01/23/2020.01.22.915389.abstract N2 - Saccharomyces boulardii is a widely used yeast probiotic which can counteract various gastrointestinal disorders1. As a relative of Saccharomyces cerevisiae, S. boulardii exhibits rapid growth and is easy to transform2 and thus represents a promising chassis for the engineered secretion of biomolecules. To establish S. boulardii as a platform for delivery of biomolecules to the mammalian gut, we measured the amount and variance in protein expression enabled by promoters, terminators, selective markers, and copy number control elements in this organism. These genetic elements were characterized in plasmidic and genomic contexts, revealing strategies for tunable control of gene expression and CRISPR-mediated genome editing in this strain. We then leveraged this set of genetic parts to combinatorially assemble pathways enabling a wide range of drug and vitamin titers. Finally, we measured S. boulardii’s residence time in the gastrointestinal tracts of germ-free and antibiotic-treated mice, revealing the relationships between dosing strategy and colonization level. This work establishes S. boulardii as a genetically tractable commensal fungus and provides a set of strategies for engineering S. boulardii to synthesize and deliver biomolecules during gut colonization. ER -