ONE of the most harmful and persistent families of pollutants, dioxins, may have a formidable foe: a bacterium that digests them.
It is the first time anyone has isolated a pure strain of bacterium that is capable of breaking down dioxins, says Michael Bunge at the University of Halle-Wittenberg, Germany. The strain could eventually be used to clean up contaminated sites that can鈥檛 be treated with existing techniques.
Dioxins are well known to be carcinogenic, but they also play havoc with the developing immune and nervous systems of children. They are a by-product of industrial processes such as incineration, paper bleaching and plastics manufacture, and are notoriously difficult to break down. As a result they can build up in the environment and enter the food chain by accumulating in animal fat. According to the US Environmental Protection Agency, people who eat high-fat foods have a greater chance of developing cancer as a result.
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The conventional means of destroying dioxins involve either burning them at high temperatures or exposing them to ultraviolet light, says Bunge. 鈥淏ut these methods are not feasible for large contaminated sites,鈥� he says.
The dioxin-busting bacterium is a strain of Dehalococcoides that was originally found in sediment in the Spittelwasser, a heavily polluted tributary of the Elbe in northern Germany (Nature, vol 421, p 357). Although the breakdown products are also toxic, they are far less persistent than dioxins and easier to clean up.
Bunge hopes other researchers will now work on developing a way of using the bug to clean up contaminated sites, but he warns it might not be easy. The strain is difficult to cultivate and they don鈥檛 understand exactly how it breaks the dioxins down.