Evolved Biosensor with High Sensitivity and Specificity for Measuring Cadmium in Actual Environmental Samples.

Area of Science:

• Environmental Science
• Microbiology
• Biotechnology

Background:

• Bacterial biosensors offer promise for contaminant detection due to sensitivity and cost-effectiveness.
• Existing cadmium-responsive biosensors lack the sensitivity, specificity, and anti-interference needed for real-world applications.

Purpose of the Study:

• To develop an advanced bacterial biosensor for detecting total and extractable cadmium in environmental samples.
• To enhance biosensor performance through directed evolution for improved sensitivity and specificity.

Main Methods:

• Constructed a cadmium-responsive biosensor using CadR regulatory and GFP reporting elements.
• Employed error-prone PCR and fluorescence-activated cell sorting (FACS) for directed evolution.
• Isolated the high-performance variant epCadR5 through five rounds of screening.

Main Results:

• The evolved biosensor (epCadR5) exhibited high sensitivity and specificity for trace cadmium detection, with a 0.45 μg/L detection limit.
• Demonstrated 6.8 times greater specificity to cadmium compared to the wild-type biosensor.
• Successfully detected cadmium in contaminated soil matrices and yielded quantitative results comparable to ICP-MS.

Conclusions:

• The engineered bacterial biosensor shows significant potential for detecting cadmium contamination in soil and water.
• The developed biosensor overcomes limitations of previous models, offering improved real-world applicability.
• Directed evolution is an effective strategy for enhancing bacterial biosensor performance.