This article describes a method for detecting specific analytes, such as lead, using genetically modified bacteria as biosensors. The bacteria express a red fluorescent protein when the presence of the analyte is confirmed through a series of steps involving surface wipes and incubation.
Begin with a tube containing a bacterial culture genetically modified to act as a biosensor.
The bacteria harbor a plasmid system with a red fluorescent protein or RFP gene under the control of a promoter. The promoter is repressed by a protein that is sensitive to the presence of a specific analyte, like lead.
Use an ethanol-based wipe to thoroughly wipe a test surface, and collect the analyte present on the surface.
Cut a small section from the center of the wipe and immerse it completely in the bacterial culture.
Incubate to facilitate the diffusion of the analyte from the wipe into the bacterial culture.
The analyte enters the bacteria and binds with the repressor protein, changing its conformation and activating the promoter.
The activated promoter initiates gene transcription, leading to the expression of the RFP.
Measure the bacterial fluorescence to ensure the presence of the analyte on the test surface.
Use an ethanol based wipe designed for removing lead to wipe all surfaces of the hands, including between the fingers. Store the wipes in an appropriately labeled sealable baggie until analysis. Use an alcohol based wipe to wipe down any large surfaces to be tested.
Use a cotton swap moistened with ethanol to wipe down any small surfaces to be tested. Wearing clean gloves and using scissors that have been cleaned with alcohol, cut a section that is approximately one square centimeter out of the center of the wipe. Then, place the cut piece of wipe, or cotton swab, directly into a culture tube containing two milliliters of the sensor bacteria, and ensure that it is completely submerged in the broth.
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