Wired Science

Some Bacteria are Challenging our Understanding of Life

Microbes reside in many places we wouldn't normally dream of visiting—take the Gakkel Ridge, for instance, where geologists are deploying robots under the Arctic ice in the hopes of finding new life forms in deep-sea vents. Microbes have been found in other odd places, too: the dry, frigid Arctic valleys, radiation-rich dead zones, and boiling hot springs, to name but a few. Despite how difficult it is to get one's hands on them, scientists around the world are studying these "extremophiles" to learn their secrets and, if they're lucky, to steal a few of them, too.

One of the first extreme microbes to make a big mark on science was Thermus Aquaticus, a bacterium first isolated from hot geysers in Yellowstone National Park. The bacterium can survive and reproduce at 150˚F, a temperature ideal for copying DNA in the laboratory (heat speeds up reactions so they can complete faster). As a result, enterprising scientists stole its key DNA-copying protein, Taq polymerase, for laboratory use. Today, Taq is used in most biological labs around the world and is one of the reasons that forensic DNA analysis is possible.

Taq, however, is not the hottest of the hot. In 2003, 200 miles from Puget Sound, scientists discovered a microbe they call "strain 121" that can survive at temperatures higher than water's boiling point—they can, in fact, reproduce at temperatures as high as 250˚F or 121˚C (hence their name). These are archaea, single-celled organisms similar to bacteria, and are the most heat-tolerant microbes ever discovered. Interestingly, strain 121 breathes not oxygen but iron oxide.   

Then there's the other extreme: cold. After a grueling search for life in the Antarctic "ice-block" lake known as Lake Vida—which, under a thick layer of ice, harbors salty water as cold as 14˚F—scientists uncovered, in 2002, microbes at least 2,800 years old. "It was some very cold drilling," scientist Peter Doran of the University of Illinois at Chicago told the National Science Foundation [http://www.nsf.gov]. "We were there for two weeks at temperatures approaching -40°F." These microbes might be very similar to those that could be found on Mars, he added—relevant given that the Mars Phoenix Lander will be searching for signs of life in the Martian arctic this May.  "Mars is believed to have a water-rich past, and if life developed, a Lake Vida-type ecosystem may have been the final niche for life on Mars before the water bodies froze solid," Doran said.

Other microbes might be able to keep us from aging as quickly. A species of bacteria called Deinococcus radiodurans was discovered in Oregon in 1956 when scientists who were attempting to sterilize food with high doses of radiation found that even extremely high doses could not kill these bacteria. Radiation contains so much energy that it can kill animals quickly at high enough doses; even at low levels, exposure is dangerous because it damages DNA and causes cancer. Scientists are therefore studying these tough microbes in the hopes of understanding why they are so good at repairing their own DNA—and to learn whether we can co-opt their skills to prevent both cancer and aging.

Other microbes were recently discovered that actually eat the byproducts of radiation. Scientists found a species of bacteria in South Africa living two miles below Earth's surface in high-pressure environments. These bacteria, existing without sun and all other forms of life, and which may have been lurking in those depths for up to 25 million years, get their nourishment from radiation byproducts produced by the reaction of uranium, thorium and potassium with water over time. They might be the oldest ancestors of current bacteria, raising the question of whether life actually began underground.

Our planet clearly harbors a diverse group of microbes living in the harshest environments imaginable—and we've probably only seen the tip of the iceberg, so to speak. As scientists continue to uncover life-forms adapted to the darkest and deadest of places, they will not only learn a thing or two about survival, but might also get a sneak peek of possible life on other planets.