(265b) Development of a Fast-Responding, Minimal-Equipment Biosensor for Zinc Deficiency
To do this, we engineered hybrid promoters that respond to both an exogenous inducer (to enable pigmentation) and zinc (to control which pigment is produced) by adding operator sites for the zinc-responsive repressor Zur to standard inducible promoters. The best-performing hybrid promoter was incorporated into circuits with other zinc-responsive elements to create a multicolor zinc sensor that is colorless during preculture and, upon induction, produces one of three pigments to indicate relative zinc concentration.
To increase clinical relevance, we next moved Zurâs switching point from its natural threshold (0.1 Î¼M zinc) to physiologically relevant serum zinc levels (5-10 Î¼M). While analyte affinity of some sensors can be readily tuned, changing a transcription factorâs affinity for its analyte by orders of magnitude without altering DNA binding activity is challenging. The most effective strategy to move the switching point was controlling Zur expression with a zinc-activated promoter. Through modulation of transcription factor expression levels, we created a library of sensors with switching points at extracellular zinc concentrations between 1 and 20 Î¼M.
Taken together, our efforts have enabled a biosensor with potential for future impact on millions of lives in the developing world, with design and tuning strategies that may be generalizable to other nutrients and sensors.