These 3 bacteria can break down toxic PCBs

Though PCBs are no longer used (they have been banned since the 1970s), they are virtually indestructible, which means they continue to contaminate rivers, lakes, and harbors worldwide, posing a threat to human and ecosystem health. (Credit: iStockphoto)

Scientists have discovered three bacteria that can dechlorinate toxic PCBs in the environment.

They’ve also designed a way to culture the bacteria in large quantities, making them even more effective.

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PCBs are synthetic organic chemical compounds of chlorine and biphenyl. They have been widely used as coolant fluids in many electrical products. However, they are toxic, and exposure to PCBs has been known to cause symptoms almost immediately.

Though PCBs are no longer used (they have been banned since the 1970s), they are virtually indestructible, which means they continue to contaminate rivers, lakes, and harbors worldwide, posing a threat to human and ecosystem health.

Currently, the only treatment available involves capping or dredging and landfilling the PCBs. An example is the ongoing SuperFund project to dredge the upper Hudson River to remove PCBs.

In this regard, the new technique to culture PCB dechlorinators could pave the way for alternative, and possibly more effective, methods of degrading PCBs on-site.

A new way to culture

The three bacteria from a genus called Dehalococcoides are added to a list of only seven enzymes known to act on chlorinated compounds.

Applying the microbes directly to break down (dechlorinate) PCBs on-site would be very effective for bioremediation. However, these microbes are extremely difficult to culture.

To overcome the culture challenge, researchers at the National University of Singapore used an alternative substrate called Tetrachloroethene (PCE) that can help boost the cell numbers of PCB dechlorinators.

He Jianzhong, an associate professor in the civil and environmental engineering department, says the discovery opens up “new possibilities of developing more effective ways of destroying PCBs in our environment.”

Scientists from A*STAR’s Genome Institute of Singapore collaborated on the research, which was published recently in the Proceedings of the National Academy of Sciences.

Source: National University of Singapore