A New Way That a Cow’s Inner World Shapes Earth’s Atmosphere
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Physics Black Holes Evolution Home A New Way That a Cow’s Inner World Shapes Earth’s Atmosphere Comment Save Article Read Later Share Facebook Copied! Copy link Email Pocket Reddit Ycombinator Comment Comments Save Article Read Later Read Later microbiome A New Way That a Cow’s Inner World Shapes Earth’s Atmosphere By Marlowe Starling July 27, 2026
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animals biochemistry biology cell biology climate science genomes genomics microbes microbiology microbiome All topics W ithin every cow is a thriving ecosystem. Churning deep in its intestines, a massive fermentation chamber known as the rumen hosts a robust microbiome that can consume up to 100 pounds of feed daily. Inside this gut pouch, tens of millions of bacteria scavenge for scraps of fiber, starch, and other nutrients, and break down cellulose and proteins. They get a hand from microbial fungi, whose enzymes demolish stiff cell walls, and all are ruled by ciliates: large, predatory microbes that gorge themselves on bacteria.
This complex food web transforms a bounty of compounds to fuel the cow’s metabolism. Little goes to waste: Even hydrogen gas and carbon dioxide, the byproducts of fermentation, are scavenged by opportunists in this dark, warm, oxygen-free world. Those opportunists are rumen microbes called methanogens, and their waste product is methane, a notoriously powerful heat-trapping greenhouse gas .
In this way, the inner world of a cow has global significance. Ruminant livestock, including cows, goats, and sheep, have burped out about a third of all methane gas in the atmosphere. All told, when combined with more methane from landfills and fossil fuels, the gas is responsible for around 30% of the rise in global temperatures over the past 150 years. But it has a weak spot: It decays more quickly than carbon dioxide. That’s why cow gas has attracted interest from researchers across the globe. They are looking into livestock’s specialized stomachs to identify the biological mechanisms that produce methane, which could be targeted to slow global warming within our lifetimes.
A recent study published in Science has revealed a clue wrapped in a membrane. Amid new genome sequences for 450 ciliates — the rumen’s apex predators — researchers followed a trail that led them to an organelle, new to science, that is essential to the biochemical process of rebuilding atoms into compounds that are heating the planet. They named it the “hydrogenobody” because it produces hydrogen gas, which methanogens then turn into methane.
The findings offer new ideas for managing this pervasive source of warming, said Juan Tricarico , who researches enteric, or intestinal, methane at Dairy Management Inc ., a nonprofit trade association for dairy farmers, and was not involved in the recent study. “Just targeting the methanogens is probably not enough.”
Understanding how microscopic organisms lead to changes at a planetary scale will require further disentangling of the rumen’s microbial food web and the specific mechanisms by which they produce methane, he added. “We want to understand the environment under which these microbes thrive.”
Even though ciliates have been studied for over a century, their role in the cow-gut ecosystem has been neglected compared to the far more numerous bacteria. Microbiologists know they are the largest single-celled organisms in the rumen. Under a microscope, their hairlike cilia sweep the area outside the cell like wispy brooms, pulling bacteria into their mouths and pushing them around. Powering all those cilia takes a lot of energy, and making that energy releases hydrogen gas, which is then consumed by bacteria and archaea, including methanogens.
“The whole rumen system is highly evolved, it’s highly synergistic, it’s highly symbiotic, and it’s evolved to consume all of that hydrogen,” said Rod Mackie , a rumen microbiologist at University of Illinois, Urbana-Champaign, who was not involved in the new study. “And they [methanogenic archaea] do it by shunting that into mainly methanogenesis.”
Save Article Read Later To better understand the specific roles of rumen ciliates in methane emissions, microbiologists have turned to genomics. In 2021, Zhongtang Yu, a rumen microbiologist at Ohio State University, sequenced the very first rumen ciliate genome from a species called Entodinium caudatum ; its genus includes roughly 90% of all ciliates in livestock rumens. A few years later, Yu assisted another team in sequencing the genomes of 52 additional rumen ciliates — a good start, but far from representative of the cow microbiome’s ciliate diversity.
So when the 2026 study in Science reported 450 new ciliate genome sequences, jaws dropped across the rumen microbiome community. (The study’s authors, most of whom are based at the Chinese Academy of Sciences or Nanjing Agricultural University, did not respond to interview requests from Quanta Magazine .) The genomes have been added to a database where any researcher can access and study the ciliate sequences.
The paper’s authors got a head start by searching the genomes for…
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