LAUSR

Heavy metals, that is Cu(II), are harmful to the environment. There is an increasing demand to develop inexpensive detection methods for heavy metals. Here, we developed a yeast biosensor with reduced‐noise and improved signal output for potential on‐site copper ion detection. The copper‐sensing circuit was achieved by employing a secondary genetic layer to control the galactose‐inducible (GAL) system in Saccharomyces cerevisiae. The reciprocal control of the Gal4 activator and Gal80 repressor under copper‐responsive promoters resulted in a low‐noise and sensitive yeast biosensor for copper ion detection. Furthermore, we developed a betaxanthin‐based colorimetric assay, as well as 2‐phenylethanol and styrene‐based olfactory outputs for the copper ion detection. Notably, our engineered yeast sensor confers a narrow range switch‐like behaviour, which can give a ‘yes/no’ response when coupled with a betaxanthin‐based visual phenotype. Taken together, we envision that the design principle established here might be applicable to develop other sensing systems for various chemical detections.