Author: Lindsey Konkel / Source: Science News for Students
From the great outdoors to our internal organs, the world is awash in unseen bacteria (some seen growing on plate here). Most people assume (unfairly) that these germs are all dangerous.
Biologists know better. Studying these poorly understood microbes could better reveal how they function as the “invisible backbone of life.”Victoria Orphan has loved the ocean for as long as she can remember. She used to snorkel in the Pacific Ocean near her family’s home in San Diego, Calif. She’d grab her mask and snorkel tube to visit the hidden world of plants and animals beneath the ocean’s surface. Orphan went to college at the University of California, Santa Barbara in the early 1990s. There she discovered something that changed the way she thought about the oceans — and life on Earth.
Another student showed her a small vial of seawater. Orphan didn’t think it looked all that interesting. It was just plain old water. Then the other student added a fluorescent chemical to the water and shined ultraviolet light on it. The tube lit up as millions of tiny bacteria began to glow. Just moments earlier, the microbes had been invisible. “These tiny organisms were all over the place,” says Orphan, “and yet we couldn’t see them. We knew almost nothing about them.”
She now spends her days exploring this hidden single-celled world. As a geobiologist at Caltech in Pasadena, Calif., she studies how bacteria and other microscopic life shape the deep sea.
Bacteria play central roles in many ecosystems. These include the oceans, soil and atmosphere. They’re also a big part of the global food web. Bacteria make it possible for all other life on Earth to exist. That’s why scientists say these single-celled organisms are the invisible backbone of all life — at least on Earth.
Yet there’s plenty we don’t know about them. Scientists think they’ve identified fewer than one percent of all bacterial species. That’s been driving Orphan and others to explore the mysteries of their one-celled world. They suspect bacteria will prove key to understanding — and protecting — Earth’s most important natural resources.
The methane eaters
Some bacteria eat really weird things. Scientists have found bacteria that eat rocks, sewage — even nuclear waste. Orphan studies a type of bacteria that live on the sea floor and gobble up methane.
Methane is a greenhouse gas. Like carbon dioxide and some other greenhouse gases, it enters the air when people burn oil, gas and coal. There are also natural sources of methane, such as natural gas, rice production and cow manure. Greenhouse gases trap heat in the atmosphere. An excess of these gases in Earth’s atmosphere has been warming the global climate.
Methane can seep out of the Earth on the sea floor. Some scientists say that even more methane would escape into the atmosphere if it wasn’t for marine bacteria. Certain of those bacteria dine on methane. That allows the oceans to trap a huge amount of the gas. “These microorganisms are the gatekeepers. They prevent ocean methane from getting into the atmosphere where it can change greenhouse-gas levels,” Orphan explains.
Finding single-celled organisms on the vast sea floor can be a challenge. Through the window of a submarine, she looks for clusters of clams and giant tube worms. These organisms signal that invisible marine bacteria live there, too. Wherever those methane-eaters live, they create new molecules as they dine. Other organisms use those new molecules as food. An entire food web springs up on the ocean floor.
Orphan and her team have found methane-eating bacteria along cracks on the sea floor, where this gas is seeping out. These cracks often happen where two tectonic plates bump into each other.
Some bacteria, they learned, can eat methane only by partnering with other single-celled organisms called archaea (Ar-KEE-uh). That important detail could help scientists better predict how much methane is escaping into the air, says Orphan.
Methane eaters aren’t the only deep-sea bacteria to interest scientists. “The deep sea is home to some pretty cool microbes,” says Jennifer Biddle. She’s a marine microbiologist at the University of Delaware in Newark. Biddle studies bacteria that live in deep ocean trenches.
These underwater canyons are some of the least-studied places on Earth. They are incredibly hard to reach. Challenger Deep wins the record for the deepest-known spot on the planet. At the bottom of the Mariana Trench, in the western Pacific, Challenger Deep sits some 11 kilometers (more than 7 miles) below the ocean surface. If Mount Everest, the world’s tallest mountain, sat in the Mariana Trench, its peak would still be more than a mile beneath the waves.
The Mariana Trench is one of the toughest places for life to survive. Zero sunlight reaches it. Its temperatures are frigid. Large animals, such as whales or fish,…
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