Methane producers in the underbrush: new research shows that fungi can also produce methane. Credit: Katharina Lenhart

Some
six years ago scientific textbooks had to be updated because of the
surprising discovery made by the research group led by Frank Keppler
that plants produce methane in an oxygen-rich environment. At that time
this was unthinkable, since it was commonly accepted that biogenic
methane could only be formed during the decomposition of organic
material under strictly anoxic conditions. His group has now made
another fascinating new observation: fungi produce methane.

Methane
is 25 times more effective as a greenhouse gas when compared with
carbon dioxide. Most of this gas is produced by bacteria in rice fields,
landfills or cattle farming. Following the study of Frank Keppler and
his colleagues in 2006 which reported that plants also produce methane,
his research team has continued to focus on methane sources. Now
Katharina Lenhart, a member of Frank Keppler’s research group at the Max
Planck Institute for Chemistry, has made another interesting discovery.
She discovered that fungi, which decompose dead organic matter, also
emit methane.

In
her study, the biologist examined eight different Basidiomycetes fungi.
Under laboratory conditions she observed methane production and
verified her finding using isotopic labelled substrates. During her
experiments she varied the culture media on which the fungi grew and
found that the underlying substrate has an impact on the amount of
methane formed. Various molecular, biological and analytical methods, in
collaborative work with the University of Giessen and the Helmholtz
Centre for Environmental Research in Magdeburg, showed that no
methanogenic microorganisms (called archaea)—which produce methane in
their energy metabolism—were involved. “Thus, processes within the fungi
must be responsible for the formation of methane,” explains Katharina
Lenhart. As yet which processes these are remains unknown.

“When
compared to other well-known methane sources, the amount of methane
released by fungi is rather low. Their contribution to global warming is
therefore classified as negligible,” says Frank Keppler. Of great
scientific interest, however, is the ecological relevance of these
results, especially since fungi are in some instances closely associated
with bacteria. Many bacteria utilize the energy-rich methane in their
metabolism. They absorb methane and oxidize it to water and carbon
dioxide. Currently unknown is the extent to which the methane released
by fungi is absorbed by these associated bacteria or whether they
benefit directly from it, concludes the biologist Katharina Lenhart.

This
work is a solid foundation for follow up studies by interdisciplinary
research teams to provide the explanation as to why fungi emit methane
to their environment.

 

Source: Max Planck Institute