Bacteria send out molecular scrounger for copper.

Wetlands and rice paddies produce large amounts of methane. However, much of the planet-warming gas never makes it into the atmosphere because bacteria in these environments feed on it, metabolizing it into methyl alcohol. Scientists have long known that to chemically crack this tough chemical, the bacteria require copper. Exactly how these microorganisms absorb copper has been somewhat of a mystery.

Now, researchers at the University of Kansas in Lawrence and the University of Minnesota, Twin Cities have isolated and characterized the organic molecule that bacteria employ for taking up copper. Dubbed methanobactin, this yellow-red molecule is shaped like a pyramid. To isolate the molecule, the researchers grew methane-metabolizing bacteria in the absence of copper. Soon, a yellowish tint appeared around the cells, and the researchers ascertained it was because the cells were secreting methanobactin.

When the investigators added copper to the mix, the methanobactin bonded to the metal and then carried it back into the cells, where metabolic proteins used it to digest methane. By binding to copper, methanobactin also renders the highly reactive metal less toxic to the cell.

By understanding how bacteria in the soil control the release of methane into the atmosphere, researchers might create better models of climate change, the researchers suggest. They describe the methanobactin molecule in the Sept. 10 Science.--A.G.