Microbe polishes off pollutant.

A soil microbe has been quietly and competently cleaning up what would otherwise be a persistent environmental pollutant, researchers report in the Nov. 8 Proceedings of the National Academy of Sciences.

Studies had established that the soil-dwelling bacterium Pseudomonas pavonaceae breaks down a pesticide residue called 3-chloroacrylic acid. Richard V. Wolfenden and Christopher M. Horvat of the University of North Carolina at Chapel Hill wanted to determine how long this residue would remain in. the environment if the bacterium didn't digest it.

By measuring the residue's decomposition rate at various temperatures, the researchers found that spontaneous decomposition would take a whopping 10,000 years to cut the residue's abundance in half--a persistence comparable to that of plutonium 239.

In contrast, an enzyme in the microbe can clear soil of 3-chloroacrylic acid in a matter of seconds.

Absent the microbe, the residue would "stick around for cons," building up in the soil and contaminating groundwater, says Wolfenden. He adds that the residue-busting activity appears to be a happy accident. The enzyme "doesn't seem to be designed with [the residue] in mind," he says.--A.C.