WASHINGTON — Life keeps popping up in the most unlikely places. In the last few days, scientists reported finding unexpected colonies of microorganisms occupying three very different regions on Earth.
According to their reports, vast numbers of invisible, one-celled creatures are:
Sleeping but still alive after 120,000 years under almost two miles of ice in Greenland.
Scientists say it's important to understand microbes because they outnumber all the world's plants, animals and insects, and are responsible for many things, from climate regulation to photosynthesis, digestion and disease. Their ability to survive in the most extreme environments boosts hopes that forms of life will be found on other planets.
``Microorganisms are ubiquitous in nature,'' said Jennifer Loveland-Curtze, a microbiologist at Penn State University. ``They are found in the deep subsurface and in the stratosphere and at all kinds of extreme environments.''
``Microbes comprise up to one-third or more of the Earth's biomass, yet fewer than 8,000 microbes have been described out of the approximately 3 million that are presumed to exist,'' she said.
In Greenland, a drilling team sponsored by the National Science Foundation discovered dormant bacteria eking out a living 1.8 miles (about three kilometers) below the island's enormous ice cap. Loveland-Curtze described the finding Tuesday at a meeting of the American Society for Microbiology in Boston.
The cells were so small that 1.5 billion of them would fit in a tablespoon. They apparently survived by feeding off nutrients in tiny veins of water inside the ice. Their metabolism was barely enough to preserve their DNA, and they'd have had enough energy to divide only once in thousands of years.
``We know that they had survived for at least 120,000 years,'' Loveland-Curtze said in an e-mail message. ``The proof that they were alive is that we grew them in the laboratory." That's a standard scientific proof and the same test that gardeners apply to seeds.
Another newly discovered habitat for hardship-loving microbes is a 36,000-mile (about 60,000-kilometer) ribbon of volcanic ridges winding along the seafloor, like seams on a baseball.
According to a report in the May 29 edition of the journal Nature, billions of bacteria and their cousins archaea thrive on what look like pillows of barren lava rocks ejected from below the Earth's crust. The microbes were spotted off the Pacific coast of South America by the research submarine Alvin, which explored the wreck of the Titanic in 1986.
Katrina Edwards, a geobiologist at the University of Southern California in Los Angeles, said the cells were so small that a billion of them could fit on 1 gram of rock (there are 28 grams in an ounce). The density of the undersea microbe population equals that found in rich farm soil, she said.
These ridges are ``potentially the largest surface area for microbes to colonize on Earth,'' Edwards said. ``It's my hope that people turn their heads and realize how much life thrives in the watery depths.''
The discovery of an even deeper environment for life was reported in the May 23 issue of Science magazine by John Parkes, a geologist at the University of Cardiff in Wales.
Two species of heat-loving, single-celled microbes were found living at temperatures up to the boiling point in mud cores extracted by a drill ship from 111-million-year-old sediments a mile beneath the North Atlantic seafloor off the Newfoundland coast.
The samples contained as many as 90 million cells per tablespoon. Sixty percent of them were alive, and 10 percent were actively reproducing.
Parkes said the cores came from the oldest, deepest and hottest marine sediments yet to be investigated. A few rare organisms have been found even farther down in South African gold mines, but not under the sea and not in such large quantities.
The Newfoundland microbes' age is uncertain. Parkes said they might have been buried in the original sediments 111 million years ago or been sucked down later into the mud from overlying seawater.