Paired Microbes Eliminate Methane Using Sulfur Pathway

Anaerobic microbes in the Earth's oceans consume 90 percent of the methane produced by methane hydrates – methane trapped in ice – preventing large amounts of methane from reaching the atmosphere. Researchers now have evidence that the two microbes that accomplish this feat do not simply reverse the way methane-producing microbes work, but use a sulfur compound instead.

"The dominant role anaerobic oxidation of methane plays in regulating marine methane makes it a significant component of the global methane and carbon cycles," the researchers report in the current issue of Environmental Microbiology. "Its importance in these cycles highlights the need to close gaps in the current understanding of the specific interaction between the microbial groups that work in consort to mediate anaerobic oxidation of methane."

In this case, the microbial consortia consist of an Archaea – a single cell organism – that consumes methane for energy and bacteria that reduce sulfates to obtain energy. The assumption has been that these microbes simply use reverse methanogenesis, the process in which methanogenic bacteria produce methane in the first place.

"Our research suggests that methyl sulfide is the intermediary used by these microbes," says Christopher H. House, associate professor of geosciences. "The Archaea take in the methane and produce a methyl sulfide, and then the sulfur-reducing bacteria eat the methyl sulfide and reduced it to sulfide."