A mysterious vial of mud taken from a New Jersey swamp may end up offering a solution to several obstinate forms of water pollution.

A few years ago, researchers in Peter Jaffe‘s laboratory noticed that ammonium, a pollutant that comes from sources including fertilizer runoff, was inexplicably disappearing from a soil sample taken from the Assunpink wetland in central New Jersey. Jaffe, a professor of civil and environmental engineering at Princeton University, suspected that an unidentified type of bacterium was breaking down the ammonium in the soil. What was especially interesting was the bacteria seemed to be converting the ammonium in the absence of oxygen — a behavior with potentially important implications for sewage treatment and other processes.