Cell-density-dependent sensitivity of a mer-lux bioassay

Area of Science:

• Environmental Microbiology
• Biotechnology
• Environmental Chemistry

Background:

• The mer-lux fusion assay is a biosensor for detecting bioavailable inorganic mercury (Hg2+).
• Previous versions of the assay had sensitivity limitations in nanomolar concentrations.
• Understanding mercury's bioavailability and cycling in natural environments is crucial.

Purpose of the Study:

• To increase the sensitivity of the mer-lux assay for detecting bioavailable inorganic mercury (Hg2+).
• To assess the utility of the enhanced assay for environmental monitoring.
• To investigate the induction of mercury-specific microbial reactions in natural waters.

Main Methods:

• Reduced the cellular biomass in the mer-lux assay from 10(7) to 10(5) cells/ml.
• Utilized a mer-lux fusion construct to detect inorganic mercury (Hg2+) via transcriptional activation.
• Tested the assay's performance with environmental samples from contaminated natural waters.

Main Results:

• Increased assay sensitivity from nanomolar to picomolar concentrations of Hg2+.
• Attributed enhanced sensitivity to reduced competing cellular binding sites for the MerR regulatory protein.
• Demonstrated that the mer-lux assay is sensitive enough for detecting Hg2+ in most contaminated natural waters.

Conclusions:

• The optimized mer-lux assay provides highly sensitive detection of bioavailable inorganic mercury.
• Mercury-specific microbial processes, including Hg2+ reduction and methylmercury degradation, can be induced in natural waters.
• These findings suggest that microbial mercury transformations play a role in the geochemical cycling of mercury.