Multicellular Drug Resistance from Synthetic Mitosis Control in Budding Yeast

Experimental modeling plays a vital role in understanding microbial drug resistance. Multicellular, biofilm- or clump-forming microbes encounter smaller local antibiotic concentrations and can survive harsher drug treatment than unicellular populations. However, how drug resistance depends on specific characteristics of multicellular populations, such as gene expression, and clump size distribution, is poorly understood. By deleting the AMN1 (antagonist of mitotic exit network) gene from multicellular S. cerevisiae, we obtained a drug-sensitive unicellular yeast strain. Assuming that AMN1 levels control clumping, we implemented a negative feedback-based gene circuit to control a synthetic copy of AMN1, mitotic progression, and consequently, clump sizes and drug resistance. This technology can be applied to extract parameters for computational models of multicellular drug resistance in yeast and has potential for testing the effect of novel drugs on a custom range of discrete multicellular yeast phenotypes.