Luminescent bacteria-based sensing method for methylmercury specific determination.

Area of Science:

• Environmental Science
• Biotechnology
• Analytical Chemistry

Background:

• Methylmercury is a potent neurotoxin and a significant environmental contaminant.
• Accurate and sensitive detection methods for methylmercury are crucial for environmental monitoring and risk assessment.
• Existing methods for methylmercury analysis can be complex and time-consuming.

Purpose of the Study:

• To develop a selective and sensitive bacterial biosensor for the determination of bioavailable methylmercury.
• To utilize a recombinant luminescent whole-cell bacterial strain for real-time monitoring.
• To establish a robust and reagent-like biosensor system with minimal batch-to-batch variation.

Main Methods:

• A recombinant luminescent bacterial strain, Escherichia coli MC1061 (pmerRBlux), engineered to respond to total mercury, was employed.
• Freeze-dried bacterial cells were used for stability and ease of handling.
• Organomercurial lyase enzyme was coexpressed to specifically cleave methylmercury, and EDTA was used to chelate inorganic mercury species, ensuring selectivity.
• Luciferase reporter system allowed for substrate-free, real-time monitoring of gene expression.

Main Results:

• The bacterial biosensor demonstrated high sensitivity and selectivity for methylmercury.
• A low limit of detection (75 ng/l or 300 pM) was achieved, enabling analysis of natural samples.
• Minimal cross-reactivity (<0.2%) with ionic mercury was observed at non-physiological concentrations.
• The assay provided results within 1-3 hours, with a high dynamic range of two decades.

Conclusions:

• The developed bacterial biosensor offers a robust, sensitive, and selective method for methylmercury determination.
• This approach simplifies mercury analysis, making it suitable for real-time monitoring and environmental applications.
• The use of freeze-dried bacteria enhances the practicality and reliability of the biosensing system.