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

Area of Science:

• Environmental microbiology
• Biotechnology
• Biosensor development

Background:

• Heavy metal contamination poses environmental and health risks.
• Bacterial resistance operons offer potential for developing specific ion detection systems.
• Green Fluorescent Protein (GFP) is a widely used reporter gene in biosensor applications.

Purpose of the Study:

• To engineer and characterize bacterial biosensors for detecting and quantifying silver (Ag+) and copper (Cu2+) ions.
• To assess the sensitivity and dynamic range of the developed biosensors.
• To establish a quantitative relationship between ion concentration and biosensor response.

Main Methods:

• Construction of bacterial strains incorporating a silver/copper resistance operon and a GFP reporter gene.
• Regulation of GFP expression via silver-activated promoter regions from the sil operon.
• Exposure of biosensors to varying concentrations of silver and copper ions.
• Measurement of GFP fluorescence intensity as a response to ion exposure.

Main Results:

• The biosensors successfully detected silver ions in the range of 40–300 µM and copper ions from 20–600 µM.
• A strong correlation (R² ≥ 0.90) was observed between ion concentration and GFP signal intensity.
• A detectable GFP signal was observed within 4 hours, with saturation at 13 hours for Ag+ at room temperature.

Conclusions:

• Engineered bacterial biosensors provide a sensitive and quantitative method for detecting silver and copper ions.
• The high correlation between ion concentration and GFP signal allows for accurate quantification.
• These biosensors have potential applications in environmental monitoring and heavy metal analysis.