UNDER THE TYRRHENIAN SEA, Italy — Fifty miles off the Tuscan coast, in a sparkling blue expanse broken only by rocky, forbidding islets, including the real-life Island of Montecristo, ancient creatures are roosting beneath the waves.
They spend their days feasting on an unlikely source of nourishment: methane, a potent greenhouse gas that leaks out of cracks in the seafloor.
Lately, researchers have been trying to put these microorganisms to work on an urgent task. If their appetites can be redirected to other sources of their favorite gas — namely, the hundreds of millions of tons of planet-warming methane emitted each year from oil and gas sites, livestock and wetlands — then they might just help slow climate change.
First, though, researchers need to better understand these microbes, which have been on this planet for billions of years but remain enigmatic in many ways.
One place they like to live is the bottom of the ocean, where methane buried inside the Earth seeps up through fissures in the seabed. In 2017, workers on fishing boats reported seeing a 30-foot jet of dirty water erupt out of the sea near Montecristo. Geologists discovered a string of offshore mud volcanoes, bubbling methane into the cerulean sea.
But nobody had tried to capture the organisms that eat the gas there until this year, when Braden Tierney and two colleagues sailed into the Tyrrhenian Sea, off the western coast of Italy, on a cool summer night.
“It is an odd feeling, floating on top of a place that violently exploded less than 10 years ago,” said Tierney, an American microbiologist, as the team’s boat bobbed in the predawn darkness.
Most of the methane in Earth’s atmosphere is produced by microbes that break down plant and animal matter in bogs, landfills and the stomachs of cows. But microbes of a different type scarf down methane. And only in recent decades have scientists started to understand how they do it.
As molecules go, methane is an odd choice for any organism to eat. It’s the main ingredient in natural gas, so there’s plenty of energy in it, as anyone who has put a match to a gas pipe can tell you. But to make use of it, microbes need to perform some challenging chemical maneuvers and expend a lot of their own energy.
Yet, once scientists began to identify and decipher the bacteria that could pull off this conversion, they started finding them everywhere: in rivers, in soil, in deep-sea vents, even in tree bark. In some environments, the bacteria gulp down methane before it ever has a chance to reach the atmosphere.
The cumulative effect of all these methane-eating microbes, or methanotrophs, as they’re called, is tremendous.
“Globally, all of the methanotrophs on the planet are consuming many times the amount of methane that humans are releasing into the atmosphere,” said James Henriksen, an environmental microbiologist at Colorado State University.
That means Earth today would probably be even hotter without these creatures. It also means that if these microbes could be made to work a little harder, they might cool the planet, like climate-warrior cousins of other microorganisms that we use to produce drugs, kill crop pests and treat wastewater.
So far, though, methane eaters have proved tricky to wrangle. Some die with the slightest exposure to oxygen. Many work symbiotically with other organisms, like a tiny team. “They’re dependent on each other and almost certainly other factors, and we just don’t know exactly what they need,” said Jeffrey Marlow, an assistant professor of biology at Boston University.
That’s why Henriksen, Tierney and a genomic scientist, Krista Ryon, have been traveling to some of Earth’s most extreme environments: They want to know whether microbes in these places might be different enough — or just plain weird enough — to help reduce the harms that fossil-fuel use and industrial-age farming have done to the planet.
The three scientists and their collaborators have collected samples from hot springs around Colorado. They have dived to volcanic seeps off Sicily, Japan and Papua New Guinea. To organize their globe-trotting, they founded a nonprofit organization, the Two Frontiers Project, that is funded by Seed Health, a maker of probiotics, and other donors.
So far, Two Frontiers has mostly searched for bacteria that eat carbon dioxide, the main greenhouse gas that is warming Earth. One strain the team found off Sicily has proved so efficient that 3 gallons of it could theoretically absorb and lock away as much carbon dioxide as a tree, though researchers are still working out how to cultivate and deploy it at scale. Now, Two Frontiers is widening its hunt to devourers of methane, which has far greater heat-trapping power than carbon dioxide, though it stays in the atmosphere for less time.
Plenty of “really amazing” methane eaters are still waiting to be discovered, said Mary Lidstrom, a professor emeritus of chemical engineering and microbiology at the University of Washington.
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