A whole-cell biosensor for the detection of gold

Area of Science:

• Geochemistry
• Biotechnology
• Environmental Science

Background:

• Geochemical exploration for gold (Au) relies on lab-based analyses (ICP-MS, INAA), causing significant delays.
• On-site analysis methods are needed to expedite gold exploration campaigns.
• The golTSB genes from Salmonella enterica serovar typhimurium are known to be induced by gold complexes.

Purpose of the Study:

• To develop and validate a biosensor for on-site gold detection.
• To engineer Escherichia coli with the golTSB operon and a lacZ reporter gene for gold sensing.
• To assess the biosensor's performance with various gold concentrations and in the presence of interfering metal ions.

Main Methods:

• Engineered E. coli expressing golTSB::lacZ for gold detection.
• Utilized colorimetric β-galactosidase and electrochemical assays for quantification.
• Tested biosensor with varying gold concentrations (0.1–5 µM) and interfering metal ions.
• Applied selective thiosulfate extraction for analyzing spiked soil samples.

Main Results:

• Accurate quantification of gold concentrations from 0.1 to 5 µM (20–1000 ppb).
• Observed cross-reactivity with other metal ions, requiring careful interpretation.
• Demonstrated accurate gold measurement in soil extracts, comparable to ICP-MS (P<0.05).
• Achieved a quantification limit of 20 ppb and a detection limit of 2 ppb.

Conclusions:

• The developed biosensor, combined with selective extraction, provides accurate on-site gold detection.
• This method significantly reduces analysis time compared to traditional laboratory techniques.
• The biosensor shows promise for practical application in geochemical exploration for gold.