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The Hottest Life on Earth
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20147 |
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Section : |
NATURAL SCIENCE
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| Issue
Date : |
2 / 1992 |
3,129 Words |
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Michael W. W. Adams
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In 1982, Karl Stetter of the University of Regensburg, Germany, reported that from the shallow marine volcanic vents off the coast of Italy, single-celled organisms had been isolated that actually thrived in boiling water. Not only did these microorganisms grow at extremely high temperatures, they required such high temperatures for the most rapid growth and to acquire the highest cell densities. Indeed, these remarkable life forms showed little if any growth at lower temperatures.
How is this possible? For over a century, the success of medical procedures has depended on boiling water to sterilize equipment, and every mother knows that boiling baby's bottle will rid it of bacterial contamination. Yet, here are single-celled organisms that not only survive, but actually thrive under those same conditions. Does this mean we will succumb to a new life-form that resists the most common means of sterilization? Fortunately, none of the microbes able to grow at 1000C (2120 F), are pathogenic, and even if they were, all of them known at present are unable to grow at 370 C (98.60 F) the normal human body temperature. So what do we know about these "boilable" microbes? Where do they come from, and just how do they differ from more conventional life-forms?
Deep Sea Vents
Well over 20 different types of extremely thermophilic or "hyperthermophilic" microbes, defined as being able to grow at 900 C (1940 F) or above, are now known. They have all been isolated from geothermally heated environments. The majority are marine organisms, although a few have been discovered in terrestrial hot springs of the type found in Yellowstone Park. Many of the marine species have been discovered near deep hydrothermal vents some 2,000-4,000 meters (6,500-13,000 feet) below sea level.
The vents themselves are a recent discovery, the first having been found in the mid-1970s at a depth of 2,500 meters (8,200 feet) along the Galapagos Rift off the western coast of northern South America. [See "Secrets Below the Seas," THE WORLD & I, November 1986, p. 184.] Similar volcanic vents have since been identified at sea-floor fault lines located along the Pacific rim and in the mid-Atlantic. At such sites, seawater permeates deep into the earth's crust, becomes super heated, and, as it rises back to the surface, picks up a variety of minerals and gases.
There are two types of vents: "Warm" vents where the temperature of the rising water is about 200 C (680F)
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