Microbiologists reveal unexpected properties of methane-producing microbe

For 40 years, scientists thought they understood how certain bacteria work together to anaerobically digest biomass to produce methane gas, important in bioenergy and the major source of greenhouse gas.

But now microbiologists in Derek Lovley's lab at the University of Massachusetts Amherst show for the first time that one of the most abundant methane-producing microorganisms on Earth makes direct electrical connections with another species to produce the gas in a completely unexpected way.

"We discovered that methane-producing archaea Methanosaeta have the ability to reduce carbon dioxide (CO2) to methane," Lovley explains. "They do this by a remarkable mechanism in which they make electrical connections with other microorganisms, something methanogens have never been known to do before."

Methanosaeta species are important for a couple of reasons, Lovley and his co-authors point out. They are so active in methanogenic wetlands that they are considered the most prodigious methane producers on the planet. This is a concern because atmospheric methane is 20 times more effective at retaining heat than CO2, and as tundra soils warm due to climate change even greater methane releases are expected. Also, methane produced in anaerobic biomass digesters is economically important as "one of the few proven, economical, large-scale bioenergy strategies" in use today, they say.