An engineered GFP fluorescent bacterial biosensor for detecting and quantifying silver and copper ions

Presented here are two engineered bacterial biosensors for detecting and quantifying silver and copper ions. The biosensors contain a silver/copper resistance operon and a Green Fluorescent Protein gene that is strictly regulated through silver activated promoter regions normally found on a silver resistance gene (sil operon). The two biosensors efficiently detected silver and copper concentrations of 40 mu M-300 mu M and 20 mu M-600 mu M respectively. A strong correlation (R-2=0.90 or above) between silver/copper and GFP signal makes it possible to quantify the ions using a linear regression. At room temperature incubation, the GFP signal of the biosensors in Ag+ saturated after 13h. However, a detectable GFP signal was seen in 4h.