An unexpected source of methane in the environment has been inadvertently discovered.
Nitrogen-fixing bacteria are the chief means by which nitrogen gas in the air is changed into a form that plants and animals can use. Roughly 10 percent of these nitrogen-fixing microorganisms contain the genetic code for manufacturing a back-up enzyme, called iron iron-only nitrogenase, to do their job.
Recent research reveals that this enzyme allows these microorganisms to convert nitrogen gas to ammonia and carbon dioxide into methane at the same time. The ammonia is the main product; the methane is only a sideline.
This enzymatic pathway is a previously unknown route for the natural biological production of methane.
The findings are reported Jan. 15 in Nature Microbiology. The senior author is Caroline Harwood, the Gerald and Lyn Grinstein Professor of Microbiology at the University of Washington School of Medicine. The lead author is Yanning Zheng, a postdoctoral student in her lab.
"Methane is potent greenhouse gas. That is why it is important to account for all of its sources," Harwood said.
In addition to being released from fossil fuels, methane also comes from microbial activity. In a single year, microorganisms, including many living in the ocean and decaying swamps, form and consume at least a billion tons of methane.
The archaea, single-cell life forms that tend to like harsh environments, are the main methane generators. To accomplish this, they avail themselves of complex chemical pathways, some of which already have been traced by scientists.
Read more at: https://phys.org/news/2018-01-unexpected-environmental-source-methane.html#jCp