PCB News Around the World

Bacteria Hungry for PCBs-Purdue

Copyright 2002 Business Communications Co.
Water Technology News
December 2002

A research team from Purdue University and the University of British Columbia has identified one of the key stumbling blocks that prevent microorganisms from decomposing polychlorinated biphenyls [PCBs], a persistent and potentially hazardous industrial chemical that commonly contaminates groundwater.

The discovery could eventually show researchers how to teach microorganisms to break down PCBs into ecologically safe molecules, a process known as bioremediation.

According to Dr. Jeffrey T. Bolin, professor of biological sciences and a member of Purdue's Markey Center for Structural Biology and Cancer Center, the obstacle to effective in situ PCB remediation is simple - bacteria can't quite digest them. "It's frustrating," Bolin says, "because if bacteria could fully digest PCBs, it might solve a worldwide pollution problem."

Bolin says the ability to remediate PCBs is vital because "the globe's entire surface is now contaminated with PCBs." PCBs accumulate in organisms, especially those in aquatic environments, which means that creatures that eat fish - like humans - are particularly likely to absorb large quantities.

PCBs were manufactured and used widely in industry for decades, but were later found to be toxic to animals and humans. PCBs are no longer manufactured in the United States, but their persistence makes them a worldwide problem because many suggested cleanup methods, such as incineration, are ineffective, sometimes even generating other toxic compounds such as dioxins.

While many harmful chemicals in the environment are naturally broken down into benign substances by microorganisms, PCBs have persisted for decades because decomposers, such as bacteria and fungi, do not find them tasty.

"PCB molecules actually look very similar to many organic molecules that certain bacteria eat," Bolin said. "But there are enough little differences that bacteria can't quite digest them. We asked ourselves: What could we do to improve bacterial digestion of PCBs?"

The group has adopted a twofold strategy to answer that question: first, identify what aspect of PCB breakdown the bacteria are having trouble accomplishing, then breed bacteria to improve their talent at accomplishing it. Bolin said the group's findings are a breakthrough for the first aspect.

Bolin says the team can now focus on improving bacteria for PCB remediation. He and his research partner, Dr. Lindsay Eltis of the University of British Columbia, believe microorganisms can learn to consume PCBs if properly bred. Eltis says the team hopes to use certain species of bacteria with a slight taste for PCBs and then "improve this trait through breeding until it's strong enough to make them consume PCBs as a food source."

If the group succeeds, it could mean the eventual end of PCBs, but Eltis emphasizes that there remain difficulties ahead. "We still have a great deal to do, and it will not be a simple matter to fit a species of bacteria to the task," he said. "But the potential environmental rewards are inspiring. If we succeed, we could get the planet back to where it was before PCBs were ever manufactured."

This research has been funded by the National Institutes of Health and Canada's National Science and Research Council. Contact: Dr. Jeffrey T. Bolin, Lilly Hall B-406A, Purdue University, W. Lafayette, IN 47907; Tel: 765/494-4922, Fax: 765/496-1189. Dr. Lindsay Eltis, The University of British Columbia, 2329 West Mall, Vancouver, B.C. Canada V6T 1Z4; Tel: 604/822-0042.