Cattle such as cows are notorious burpers. A single bovine can belch out as much as 220 pounds of methane in a year. Why their burps are so potent seems to have to do with a special structure inside microbes living in their gut—something researchers are calling the “hydrogenobody,” according to new research. The findings could help scientists trying to combat how much methane cattle emit—methane is a greenhouse gas, and the animals are one of the top agricultural sources of these emissions.
Like you, cattle have a microbiome. Among the microbes in their gut are a group of microorganisms called “rumen ciliates” that help the bovines digest food and are named for the rumen, the stomach compartment they inhabit, and the cilia, or tiny hairs, that cover their surface. Scientists have suspected for years that these microbes were involved in making methane in cows’ gut, but exactly how they were involved was a mystery.
New research could hold the key. In a paper published on Thursday in Science, researchers describe how hydrogenobodies in rumen ciliates in the guts of dairy cows remove oxygen and produce hydrogen—which other microbes then use to make methane.
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A three-dimensional fluorescence of the rumen ciliate Isotricha prostoma.
Chuanqi Jiang, Jinying He, and Che Hu / Institute of Hydrobiology, Chinese Academy of Sciences
The study offers a “mechanistic breakthrough” in our understanding of methane emissions from cows, says Ermias Kebreab, a professor of animal science and an associate dean at the University of California, Davis, who was not involved in the study.
Methane is a key greenhouse gas—nearly 30 times more effective at trapping heat in the atmosphere than carbon dioxide. Across the world, livestock production is estimated to be responsible for nearly 15 percent of greenhouse gas emissions—most of which are methane.
To identify the hydrogenobody—and confirm its role in methane production—the new study’s authors combined genetic analyses of hundreds of rumen ciliate genomes with detailed imaging of the microbes, as well as real-life methane measurements from dairy cows.
“We were somewhat surprised by how clearly this structure links cell biology to methane emissions,” says Jie Xiong, a co-author of the study and a professor at the Institute of Hydrobiology at the Chinese Academy of Sciences. The team found that rumen ciliates with more of the hydrogen-producing structures helped generate more methane than microbes with fewer hydrogenobodies did.
A 3D fluorescence of the rumen ciliate Dasytricha ruminantium.
Chuanqi Jiang/Jinying He/Che Hu/Institute of Hydrobiology, Chinese Academy of Sciences
The findings track with previous research showing that methane-producing microbes called methanogens that can also live in cattle’s gut tend to congregate close to microbes that produce hydrogen, Kebreab says, “but this shows the mechanism by which the hydrogen is produced.”
Knowing exactly where hydrogen is coming from inside cattle could help develop new ways of tamping down their methane-heavy burps, Xiong says, including by tweaking how the hydrogenobody itself works.
“While these ideas are still at an early stage, our work provides a clearer mechanistic framework that could guide future efforts to reduce methane emissions in ruminants,” Xiong says.