The "Methane Paradox".

• Author: Gorder, Pam Frost
• Position: EYE ON ECOLOGY

SCIENTISTS vastly have underestimated the number of places methane-producing microbes can survive and, as a result, today's global climate models may be misjudging the amount of methane being released into the atmosphere, suggests a study of a Lake Erie wetland. In the journal Nature Communications, researchers at Ohio State University and their colleagues describe the discovery of the first known methane-producing microbe that is active in an oxygen-rich environment.

Oxygen is supposed to be toxic to such microbes, called methanogens, but the newly named Candidatus Methanothrix paradoxum thrives in it. In fact, 80% of the methane in the wetland under study came from oxygenated soils. The microbe's habitat extends from the deepest parts of a wetland, which are devoid of oxygen, all the way to surface soils.

"We've always assumed that oxygen was toxic to all methanogens," says Kelly Wrighton, project leader and professor of microbiology at Ohio State. "That assumption is so far entrenched in our thinking that global climate models simply don't allow for methane production in the presence of oxygen. Our work shows that this way of thinking is outdated, and we may be grossly underac-counting for methane in our existing climate models."

More work needs to be done before researchers can determine exactly how much more methane is out there, but the microbe's habitat appears to be global. Searching publically available databases, the researchers found traces of Candidatus Methanothrix paradoxum in more than 100 sites across North America, South America, Europe, and Asia. The organism lives in rice paddies, wetlands, and peatlands--even as far north as the Arctic. It just had not been cataloged before, and its unusual metabolism had not been discovered.

Researchers long have known that wetlands are Earth's largest natural source of methane. They have placed estimates on the amount of methane produced globally based on the notion that only the oxygen-free portion of any wetland could harbor methanogens. In just the last decade, ocean researchers have seen evidence of methane being produced in oxygenated water, and dubbed the phenomenon the "methane paradox," but no microorganism has been found to be responsible. The newly discovered wetland microbe is the first such organism ever found. That is why Wrighton and her team named it Candidatus Methanothrix paradoxum.

The researchers were not...