Team:UANL Mty-Mexico/Project/detection

Detection

The genetic circuit used to build our arsenic biosensor is based on the Ars operon, which naturally occurs in E. coli. Ars operon detoxifies from arsenic, antimony and bismuth by pumping them out of the cell (Kaur et al. 1992). Briefly, the ArsR repressor normally inhibits the operon's expression; when arsenic is around, it binds the ArsR repressor therefore activating expression from pArsR (figure 1a)(Wu & Rosen 1993). Our biosensor uses this regulatory mechanism, coupled to firefly's luciferase as a reporter gene, to semi-quantify arsenic (figure 1b).

Figure 1. a) Ars operon b) arsenic biosensor.

To achieve a better sensitivity, a 10 times more active mutant luciferase from Photinus pyralis (Fujii et al. 2007) will be used. 

Why luciferase?

Fluorescent proteins are dynamic reporter genes, useful for cellular assays but not proportional to the amount of activator. On the other hand, luciferase is an ideal reporter gene for experiments requiring high sensitivity, reproducibility and quantifiable results; i.e. the light emitted is proportional to luciferase expression (Devgan 2009).