Microbiologists reveal unexpected properties of methane-producing microbe

Nov 18, 2013
UMass Amherst microbiologists discovered that Methanosaeta have the ability to reduce carbon dioxide to methane by a remarkable mechanism in which they make electrical connections with other microorganisms, something methanogens have never been known to do before. Credit: Dale Callahan and Amelia-Elena Rotaru

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.

Lovley and colleagues, including former postdoctoral researcher and first author Amelia-Elena Rotaru, describe the newly discovered properties of the -producing bacterium Methanosaeta in the current issue of the British Royal Society of Chemistry journal, Energy and Environmental Science.

"We discovered that Methanosaeta have the ability to reduce carbon dioxide (CO2) to methane," Lovley explains. "They do this by a remarkable mechanism in which they make 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 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.

Methane-producing microbial communities have been studied for decades, Lovley notes, "but all this time we were missing a major pathway of methane production." His group's study of Methanosaeta started when they found that digesters converting brewery wastes to methane contained large quantities of the microorganism Geobacter. Geobacter cannot produce methane, but it does break down more complex substrates to compounds that methane-producing bacteria can use.

The UMass Amherst teams knew from previous studies that Geobacter grow electrically conductive filaments known as microbial nanowires, which can transport electrons outside the cell to make electrical connections with minerals, electrodes or other cells. Methanosaeta were the dominant methane-producing microorganisms in the digesters and known to convert acetate to methane, but analysis of the gene expression in the digester revealed that Methanosaeta were also highly expressing genes for converting carbon dioxide to methane. The researchers speculated that Geobacter were feeding Methanosaeta electrons through their nanowires to promote Methanosaeta's methane production from CO2.

Further studies in which individual Geobacter and a Methanosaeta species were cultured together confirmed these suspicions, Lovley says. He and colleagues used radioactive tags to demonstrate that CO2 was being reduced to methane. They dubbed this transfer via microbial nanowire "direct interspecies electron transfer," or DIET. It was confirmed when they used a strain of Geobacter genetically altered to prevent it from producing nanowires, and the process did not work.

Lovely says the discovery of DIET challenges the concept held for decades that natural methane-producing microbial communities primarily exchange electrons through the production and consumption of hydrogen gas. DIET is a much more direct, and potentially more efficient mechanism for feeding electrons to methane-producing bacteria. "Now we need to improve predictions of how methane-producing microbial communities will respond to climate change. Microbial communities using DIET may react much differently than those that rely on hydrogen exchange," he says.

There are also short-term practical implications. "Once you realize that there are methane producers that can directly feed on electrons, you start thinking differently about how to optimize methane production from wastes," the microbiologist notes. "Although generating methane from wastes is one of the oldest bioenergy strategies and is practiced even in small villages in developing countries, its application on a large scale has been limited because it is slow." Trying to speed in large-scale operations can disrupt the microbes' highly coordinated activity and systems can fail.

These communities evolved over billions of years to slowly convert organic matter to methane, Lovley explains. "Electrical circuitry that evolved for microbes to make methane from organic matter in swamps at their own leisurely pace may not match our wish for a faster process in waste digesters. Just as you need to upgrade electrical service in your house when you add more appliances, we made need to use synthetic biology or other engineering approaches to increase the capacity to move current through methanogenic in digesters."

With the Massachusetts Department of Environmental Protection planning to begin in January 2014 phasing in a requirement that large-scale food service operations such as grocery stores, universities and correctional facilities compost food waste to increase diversion from landfills by 350,000 tons per year by 2020, anaerobic biodigesters may soon be very important to the state's business community. The new advances from UMass Amherst research could help to significantly improve their design and efficiency, Lovley notes.

Explore further: Halliburton pays $1.1 bn for Gulf of Mexico BP spill

More information: pubs.rsc.org/en/Content/Articl… E42189A#!divAbstract

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baudrunner
1.8 / 5 (5) Nov 18, 2013
Wikipedia states:
Natural gas is a fossil fuel formed when layers of buried plants and animals are exposed to intense heat and pressure over thousands of years.
What B.S. In the same article is stated that "Biogenic gas is created by methanogenic organisms" and "thermogenic gas is created from buried organic material". As I see it, and some researchers have proved this by recreating conditions in the lab, methanogenic organisms "feed" on the ferrite substrata within the Earth's crust, producing hydrocarbons as a waste product, and gases as described in the article. The notion that oil is produced by rotted carcasses and deteriorated organic material is just plain bunk. The stubborn refusal to shift that paradigm is counterproductive to promoting good science. All that notwithstanding, there is still evidence for the abiogenic hypothesis, which explains the vast quantities of hydrocarbons raining down on Titan, where no known organic process is at work.
baudrunner
1 / 5 (4) Nov 18, 2013
Beyond the myriad ways by which the hydrocarbon deposits have formed, we can conclude that this can be seen to support the anthropogenic theory of creation, that consciousness must evolve as a necessary predisposition to the idea that begat it all, the idea being that anything existing is so staggeringly awesome and profound of itself that it vents creation as a fractal expression, or impression, if you will. That idea is a premonition, not requiring the function of time, which with space and matter are all created at the same time. Consciousness is a predisposition to that premonition, and occurs as a matter of course. Carbon-based organics abound in the Universe.
Mike_Massen
1 / 5 (3) Nov 19, 2013
baudrunner makes idle claims
"..The notion that oil is produced by rotted carcasses and deteriorated organic material is just plain bunk.."
Wrong !

Experiments have demonstrated long ago that various organic matter subject to pressure & high temps (without bacteria) does in fact produce oils & combustible gasses in the presence of strata. ie Fossil fuels.

But, you do say "rotted" so you accept bacterial activity (at first) breaks down proteins. If you then subject these 'waste' products & bacteria to the conditions present in strata as described above you will get oil/gas - it just takes time.

This doesn't mean other reactions don't occur as bacterial species are known do produce useful products.

But to call it BS/bunk, is ignorant unscientific blurting, offer a rationale as to why and you might be taken credibly (for a change) ?

Did I read your comment/implication correctly re "abiogenic", you claiming this ?
http://en.wikiped...biogenic

baudrunner
1 / 5 (2) Nov 19, 2013
Experiments have demonstrated long ago that various organic matter subject to pressure & high temps (without bacteria) does in fact produce oils & combustible gasses in the presence of strata. ie Fossil fuels.
Yes, in the lab, but out in the open carcasses get eaten by scavengers and dry out quickly. I did also mention that there are many processes that produce hydrocarbon deposits, including the abiogenic one. The theory that dead plant and animal material are the origins of oil is as ancient as the science of paleontology, and hopelessly outdated. Just another example of refusal by the ignorencia to shift the paradigm into a more plausible scientific one.
Mike_Massen
not rated yet Nov 22, 2013
baudrunner continues his run of bad thinking and narrow attempts at imagination with
Yes, in the lab, but out in the open carcasses get eaten by scavengers and dry out quickly. I did also mention that there are many processes that produce hydrocarbon deposits, including the abiogenic one. The theory that dead plant and animal material are the origins of oil is as ancient as the science of paleontology, and hopelessly outdated. Just another example of refusal by the ignorencia to shift the paradigm into a more plausible scientific one.
R u baudrunner under the impression carcasses are few and not subject to sedimentation before they 'dry out', doent that depend on relative humidity - thought about that - not all deserts u know ?

Lots of lignin and other cellulosic biomass compressed and covered with sedimentation, thought of that too - have you ?

If it works in the lab on the small scale it can easily work in nature and especially so if you factor in humidity & source :-)