A THREE-PRONGED TOOL FOR DNA, SMALL MOLECULE, AND PROTEIN DETECTION
We repurposed a prokaryotic two-hybrid system into a versatile detection tool. Two-hybrid systems are a well-established tool for screening protein-protein interactions in yeast and bacteria; however, there is little precedent of using these systems for detection. By swapping bait and target proteins for single-chain antibodies and dCas9, we have adapted a bacterial two-hybrid system as a modular E. coli-based detection platform for small molecules, proteins, and DNA. While most whole-cell detection methods indicate the target molecule’s presence by activating a visible reporter, our system initiates transcription of a downstream gene. This allows us to activate gene expression in response to a specific signal, effectively turning any DNA sequence, small molecule, or protein into a potential transcription factor. This holds tremendous promise as a safety mechanism for engineered bacterial strains: if an undesirable mutation or molecular product is detected within a cell, our system can kill the cell by activating an apoptotic gene, or express a fluorescent protein for live-cell sorting.