JoVE Encyclopedia of Experiments
Microbiology
0 views • 4:26 min • October 30th, 2025
Begin with an assay setup containing vials placed inside an anaerobic chamber.
Each vial contains media supplemented with sodium nitrate, mercury ions, and varying concentrations of magnesium sulfate.
Rotate the setup to mix the components, then incubate.
During incubation, magnesium sulfate promotes the formation of non-bioavailable mercury complexes, reducing free, bioavailable mercury ions in a concentration-dependent manner.
Next, add induced biosensors, genetically engineered bacteria carrying a plasmid, and mix.
The plasmid contains a mercury-responsive transcriptional regulator and a promoter linked to a fluorescent reporter gene.
Under anaerobic conditions, the bacteria utilize nitrate for respiration.
Free mercury ions enter the cells, bind the transcriptional regulator, and activate the fluorescent gene, producing fluorescent proteins.
Transfer aliquots from each vial into a multi-well plate.
Using a plate reader, measure the fluorescence intensity.
A decrease in fluorescence with increasing magnesium sulfate concentrations confirms the biosensor’s ability to detect changes in bioavailable mercury.
Before starting the experiment check the anaerobic monitor to ensure that there is no
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