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Fall 1998

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Some Like It Hot
By Judy Bolyard Purdy

It's more like science fiction than fact: Some microorganisms thrive in steamy-hot underwater volcano vents and geysers like Old Faithful.

"Even scientists say, 'These really grow in boiling water? That's unbelievable,'" said biochemist Michael Adams, a UGA research professor who began studying heat-loving, or thermophilic, organisms a decade ago, shortly after their discovery.

Collectively called Archaea, they are harmless to other organisms and may be related to Earth's earliest life forms (Research Reporter, Spring 1992). Thermophilic organisms are slowly evolving, said Adams, who published the book Thermophiles, the Keys to Molecular Evolution and the Origin of Life? with UGA microbiology professor Juergen Weigel in 1996.

Since 1995, scientists have determined the complete DNA sequence - or genome - of about 40 organisms, including four high-temperature Archaea.

"It's definite," Adams said. "The genome sequences of Archaea are proof positive for recent theories that they are the third domain of life, in addition to bacteria and higher organisms. Archaea have some unique genes, some similar to those in bacteria and some similar to those in higher organisms."

Archaea also have enzymes that are stable at high temperatures.

"You can boil some of these enzymes for long periods, even days, and they're still intact and active," he said. "Compare that to what happens to an egg, which also contains enzymes and proteins."

Adams and his collaborators isolate enzymes from high-temperature Archaea such as Pyrococcus furiosus -which means "furious fireball" - and compare them to enzymes from conventional bacteria to find out why they're different.

So, what's the secret?

"The two types of enzymes are virtually identical in structure, which was very surprising," he said. "But there are numerous and very subtle [chemical] differences in their structures. That's what determines the dramatic differences in stability."

Surprisingly, one enzyme Adams and his UGA colleagues isolated from Pyrococcus breaks down nerve gas. The U.S. Army, for one, is interested in these findings, published in the Journal of Bacteriology in September.

Heat-stable enzymes have potential use for biotechnology. But for now, Adams and his collaborators at North Carolina State University and the University of Washington have a National Science Foundation grant to study the exobiological significance of high-temperature Archaea. What they learn could help scientists look for extraterrestrial life.

"I didn't think I'd ever write a grant proposal with the word extraterrestrial in it and actually mean it, and I did," he said. "What's more, it was funded."

e-mail Mike Adams at adams@bmb.uga.edu or access http://adams.bmb.uga.edu/


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