They like the cold, they don't need much oxygen, and you can fit 62 trillion of them into a teaspoon.

They're also 120,000 years old.

Those are the salient characteristics of a new species of ultrasmall bacteria discovered deep inside a glacier by researchers at Penn State University.

The Chryseobacterium greenlandensis were isolated from an ice core from 1.8 miles beneath the surface of a glacier in Greenland.

Jennifer Loveland-Curtze, the lead researcher on the Penn State team, said the new species adds one more sliver of enlightenment to the vast and mostly unexplored universe of microorganisms.

Microbes make up a third of all living material on Earth, Dr. Loveland-Curtze said, "yet fewer than 8,000 microbes have been described out of the approximately 3 million that are presumed to exist."

Only 1 percent of all the microorganisms that live inside the human body have been identified, she said, and the proportions are not much different in the rest of nature.

The Greenland ice core was extracted 13 years ago, initially to study climate and temperature changes over tens of thousands of years by examining the gases and isotopes trapped inside the different strata of ice.

But the ice also was peppered with dust picked up from the Earth or the air as the glacier formed, and each gram of airborne dust contains millions of microbes, Dr. Loveland-Curtze said.

Her lab at Penn State's Department of Biochemistry and Molecular Biology, headed by Jean Brenchley, was able to get a 120,000-year-old ice sample from Penn State geoscientist Todd Sowers, she said. Microscopic examination showed there were tiny creatures inside, including some that were probably in the ultrasmall bacteria group.

In this minuscule world, she said, each bacterium is 10 to 100 times smaller than E. coli, the common bacteria found in the human digestive system.

With the help of fellow researcher Vanya Miteva, the team carefully melted the ice, but kept it cold, filtered it, and then grew the bacteria in a low-oxygen environment for several months.

Among the hundreds of resulting colonies were three novel strains of the rod-shaped Chryseobacterium greenlandensis, as the team decided to call them. The new species became one of just 10 species officially described in glaciers around the world, Dr. Loveland-Curtze said.

No one knows where the microbes originated, she said. They could have been living in Asian deserts, volcanic dust, ocean vapors or the permafrost beneath the glacier.

During their thousands of years at the bottom of the glacier, they survived at 16 degrees Fahrenheit, she said, probably not growing that much, but repairing enough damage for the cells to hang on.

Despite how small they are, the bacteria have enough genetic machinery to adapt to many different temperatures and food sources, Dr. Loveland-Curtze said, and that lends credence to the idea that life on Earth could have begun with organisms as tiny as these.

In separate research reported last week, scientists at Woods Hole Oceanographic Institution in Massachusetts reported finding huge colonies of bacteria living on rocks on the dark, cold floor of the ocean, and surmised life could have started there, rather than in the shallow, sunlit waters that others have hypothesized.

No matter which answer is right, it simply underscores the importance of microorganisms to all life, Dr. Loveland-Curtze said.

"We are totally dependent on microorganisms for our survival," she said. "They inhabit Earth and they inhabit us, and we couldn't live without them.

"It's just amazing that something so small can accomplish so much. I guess that's why I come to work each day."