Hottest Life-Form Found: Microbe Thrives When Boiling

John Roach
for National Geographic News
May 21, 2004

Some can take the heat better than others. Scientists have discovered a deep-sea microbe that continues to grow and reproduce inside a high-pressure oven heated to 121 degrees Celsius (250 degrees Fahrenheit). Now they're wondering just how much heat the hardiest life-forms can take.

The microbe, known unofficially as Strain 121, is found where most such heat-loving microbes are found—several miles beneath the ocean surface, snuggled up in the walls of hydrothermal vents that spew mineral-enriched, scalding water.

Last year Derek Lovley, a professor of microbiology at the University of Massachusetts, Amherst, and Kazem Kashefi, a postdoctoral researcher, isolated Strain 121 from a chunk of vent that had been hauled from the ocean floor.

When the researchers placed it inside a high-pressure cooker called an autoclave—normally used to sterilize medical equipment at 121 degrees Celsius (250 degrees Fahrenheit)—the strain continued to grow and reproduce.

"That temperature was known to kill all previous life," Lovley said. "So getting over that level is an increase of how high the temperature can be before life can't exist."

Though it stopped reproducing and growing at 121 degrees Celsius, Strain 121 remained stable at 130 degrees Celsius (266 degrees Fahrenheit).

Previously, the upper known temperature limit for life had been 113 degrees Celsius (235 degrees Fahrenheit), a record held by another heat-loving microbe called Pyrolobus fumarii.

Craig Cary, an expert on high-temperature microbes at the University of Delaware in Lewes, said the discovery of Strain 121 is an "incredible" feat. But he suspects microbes that exceed the 121 degrees Celsius barrier are still to be found.

"This is not a needle in the haystack, this is a needle in the whole haystack of Kansas—there's got to be others out there," he said.


The sample of Strain 121 cultured by Lovley and Kashefi was collected from a hydrothermal vent about 200 miles (322 kilometers) off of Washington State and nearly 1.5 miles (2.4 kilometers) deep in the Pacific Ocean.

A crew of University of Washington scientists led by oceanographer John Delaney used a remotely operated submarine to retrieve the sample from the Juan de Fuca Ridge. the ridge is a lightless seascape where spewing vents called black smokers rise up like three- and four-story chimneys.

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