Plumbing the depths

A new fluorescent probe for the toxic heavy metal lead has been developed by Chuan He and colleagues at University of Chicago and the Brookhaven National Laboratory in New York. The technique exploits the fact that lead is non-toxic to the microbe Ralstonia metallidurans. The microbe releases protective proteins in the presence of lead ions, which He and his colleagues have used to produce a quick and simple detector that responds to the presence of lead ions by producing a fluorescence signal. A "scout" protein, PbrR, made by R. metallidurans"keeps a lookout" for lead ions and switches on the microbe's lead-resistance gene. The researchers worked with the closely related protein PbrR691 instead of PbrR as it can be produced in large quantities more easily.