The Biodesign for the Real World project initially started out with arsenic bioreporters for environmental arsenic detection in collaboration with the laboratory of Prof. Jan van der Meer. We then expanded our repertoire in time for the Winter School of 2016 to include mercury, zinc/cadmium, and alkanes. In Switzerland, we also have a site, historically contaminated by mercury in industrial discharge. This is why we wanted to make the mercury reporter for us.
Mercury in its Hg(II) (or Hg2+) form has toxic effects on humans, but most of what humans (and other living creatures) absorb is in an organic form (organomercury) that is generated from Hg2+ by microbes in the environment. Methylmercury poisoning in the residents of Minamata occured as over years, they ate fish that had been bioaccumulating methylmercury, which was derived from discharged industrial waste water that fed the Minamata bay. The acknowledgment of the causal effect of mercury poisoning resulted in an international convention to prevent such tragedy from happening again.
Inspired by the local needs, and research by Vanessa Lorenzo, with whom we collaborated on the Camera Obscura and the Artefacts of the Invisible, we moved forward on reporter bacteria that can detect organomercury compounds, as we could not detect Hg(II) in the soil samples provided to us from Valais by Vanessa using the mercury reporter bacteria.
Several bacteria possess alkyl mercury lyases, a family of enzymes that removes the organic group to release Hg2+. MerB is adapted for cloning from GenBank Accession Number M15049. With the help of Prof. Jan van der Meer and Vladimir Sentchilo in his lab, we made both an eGFP reporter, as well as a luxCDABE reporter, the signal detectable as luminescence.
The cloning was completed one year ago, and we obtained clones that were confirmed for detecting mercury chloride Hg(II)Cl2, but we had not followed through with testing the new clones for their ability to report eGFP or bioluminescence upon exposure to organomercury compounds.
One of the reasons it took some time was because it took some paperwork to order the compound, and we took the time to go through the safety procedures for handling the methylmercury chloride (test compound), which is toxic as it can be absorbed through the skin and mucous membranes. Dimethylmercury, which is more hydrophobic and able to pass through gloves and skin more readily than methylmercury, killed a researcher in 1997.
This is certainly something to consider when handling known mercury-contaminated samples, especially in a DIY environment. Ventillation, protection, and waste management, for starters. In a university laboratory, we used a chemical hood, double gloves over lab coat sleeves so no skin is exposed, and we asked for professional disposal of the waste.
We now tested side-by-side methylmercury chloride vs mercury chloride, on the parental strain, as well as the new strains where we introduced the merB gene for the lyase.We confirmed that both strains can fluoresce/luminesce once it sees Hg2+. However, only in the strains with the merB gene, do we have a signal if we give mercury in the methylated form.
We are now ready to test methyl-mercury from real samples.
More information can be found and will be updated on our mercury stub on our wiki.