All Organisms Produce Methane

Methane is a potent greenhouse gas, so the study of its natural and anthropogenic biogeochemical sources and sinks is of enormous interest. For many years, scientists considered methane to be produced only by single-celled microbes called Archaea, upon decomposition of organic matter in the absence of oxygen (anaerobic).

Now, a collaboration of earth and life scientists led by Frank Keppler and Ilka Bischofs has shown that an enzyme is potentially not necessary for methane formation, as the process can also take place via a purely chemical mechanism. "Methane formation triggered by reactive oxygen species most likely occurs in all organisms," explains Leonard Ernst, an interdisciplinarily trained junior researcher who conducted the study. The scientists verified the reactive oxygen species-driven formation of methane in more than 30 model organisms, ranging from bacteria and archaea to yeasts, plant cells and human cell lines.

It was a sensation when Max Planck researchers discovered the release of methane from plants in the presence of oxygen (aerobic) 16 years ago. However, initially the results were doubted, since methane formation could not be explained with the then existing knowledge about plants. When researchers observed that also fungi, algae and cyanobacteria (formerly blue-green algae) formed methane under aerobic conditions, enzymatic activities were assumed to be responsible. However, the researchers never found a corresponding enzyme in any of these organisms. "This study is therefore a milestone in our understanding of aerobic methane formation in the environment," said Frank Keppler, a geoscientist at Heidelberg University. "This universal mechanism also explains the observations of our previous study on the release of methane from plants," adds Keppler.

Read more at Max-Planck-Gesellschaft

Image: All organisms produce methane in a chemical process involving free radicals. (Credit: Max Planck Institute for Terrestrial Microbiology/Ernst)