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Scientists uncover second way bacteria make methane

New research shows that bacteria have a previously unknown way to make methane, a discovery that could have both ecological and medical implications.

Researchers from various U.S. universities have discovered a new way microorganisms produce natural methane, according to recent research published in the journal Nature Microbiology.

Nitrogen-fixing bacteria are the main way natural nitrogen gas transforms into a form that humans and plants can both process. Of all those bacterial species, nearly 10 percent have the genetic code to create a back-up enzyme known as iron-only nitrogenase.

In the new research, scientists found that the enzyme enables bacteria to convert nitrogen gas to ammonia and carbon dioxide into methane at the same time. The ammonia is the main product of that process, and methane is simply a side effect. That means the newly discovered enzymatic pathway is a previously unknown channel for the natural biological production of methane.

“Methane is potent greenhouse gas. That is why it is important to account for all of its sources,” said study co-author Caroline Harwood, the Gerald and Lyn Grinstein Professor of Microbiology at the University of Washington School of Medicine, according to

Methane is released from fossil fuels, but it is also generated from microbial activity. In fact, microorganisms form and consume at least a billion tons of methane per year. As a result, further study of the gas could have large ecological significance.

This research could also be important for the medical community because methane plays a role in the interactions between the microbes that inhabit humans and animals. For instance, scientists suspect methane in the gut contributes to certain digestive disorders.

This new finding builds on previous research that shows iron-only nitrogenase is active in microbes more often and in more conditions than previously thought. The team found it in the microorganism Rhodopseudomonas palustris, as well as three other nitrogen-fixing bacterial species that create the enzyme. They hope to expand on the study to see what else they can learn about the new pathway, as well as find what other applications it might have. 

“Our findings are significant because they give scientists a second target to chase in understanding biological methane formation and rising methane emissions,” said study co-author Lance Seefeldt, a professor in Utah State University’s Department of Chemistry and Biochemistry, in a statement. “In addition, the discovery could drive efforts to turn waste gasses into usable fuels.”

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