House, working with James J. Moran, graduate student in geosciences now at McMaster University; Emily J. Beal, graduate student in geosciences; Jennifer M. Vrentas, a Penn State undergraduate at the time; Katherine Freeman, professor of geosciences, all at Penn State, and Victoria J. Orphan, assistant professor of geobiology, California Institute of Technology, first investigated the assumption that reverse methanogenesis was the method used by the microbes. They provided hydrogen to the consortium and checked to see if methane oxidation decreased. If hydrogen were the interspecies transfer molecule, than an abundance of hydrogen would turn off the methane oxidation.
"We observed a minimal reduction in the rate of methane oxidation, and conclude that hydrogen does not play an interspecies role in anaerobic oxidation of methane," the researchers say.
They then tried the methyl sulfides, methanethiol (methyl mercaptan) and dimethyl sulfide, to see if they reduced methane oxidation. The researchers found that methanethiol reduced oxidation. The researchers also substituted carbon monoxide for methane and found that the Archaea could oxidize that as well and produce these sulfur compounds.
"In climate models, researchers generally only consider the methane produced in bogs and lakes as dominant greenhouse gases," says House. "They do not need to consider ocean methane because these microbes destroy most of it before it is released from the sediments."
|Contact: A'ndrea Elyse Messer|