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UI researcher's study on termite bacteria may aid in greenhouse gas
IOWA CITY, Iowa -- Most people would rather see wood-eating termites
completely exterminated. However, these insects' digestive processes that
prove so maddening to homeowners may provide insight into why some animals
produce more greenhouse gasses than others, said a University of Iowa researcher
whose work appears in the Jan. 29 issue of Science.
Jared Leadbetter, Ph.D., a UI postdoctoral associate of microbiology,
has built upon earlier studies that found wood-feeding termites digest
their fiber-rich food in a highly productive manner and, consequently,
emit less methane into the atmosphere than expected. Methane is a potent
greenhouse gas and a major contributor to global warming, according to
the U.S. Environmental Protection Agency (EPA). In comparison to termites,
cattle, which also have a diet rich in fiber, are less efficient. As much
as 20 percent of the energy contained in the grass that cows chew is later
emitted into the atmosphere as methane.
Scientists do not understand which factors lead to these two very different
outcomes. Learning more about termites could lead to improvements in cattle
nutrition and decreases in their methane emissions, Leadbetter said.
As a contributor to global warming, methane is second only to carbon
dioxide, according to the EPA. Over the last 200 years, methane concentrations
have more than doubled, largely due to human-related activities. Livestock
are among the largest sources of methane from human-related activities.
The roughly 100 million cattle in the United States produce about six million
metric tons of methane into the atmosphere annually, the EPA found.
In the article that appears in Science, Leadbetter and his colleagues
investigated bacteria known as spirochetes that are found in termites'
guts. Leadbetter and his colleagues conducted the research at Michigan
State University, where Leadbetter pursued his doctoral and post-doctoral
studies. Leadbetter came to the UI in June 1998.
The scientists found that these spirochetes consume hydrogen, a key
intermediate produced during the digestion of plant fiber. The spirochetes
nourish the termites by converting the hydrogen into acetate -- an excellent
food source for both termites and cows. In cows, the spirochetes apparently
are absent or unable to convert the hydrogen into acetate because such
hydrogen is converted into methane.
"Comparing them mouthful to mouthful, the termite is more efficient
than the cow," Leadbetter said. "These spirochetes help to explain
this. By conducting basic science we have learned things about the termite
that may have productive applications down the road. For instance, other
researchers might be stimulated by our results to find novel ways to improve
the nutrition of cattle."
Leadbetter also noted that the spirochetes' beneficial role in termites
contrasts with the notorious roles of other spirochetes as "germs"
causing syphilis and Lyme disease. By performing studies on diverse subjects
such as the termite gut, scientists hope to continue to discover new microbes
that carry out previously unappreciated, but beneficial roles in nature.