MICROBE COULD YIELD CLUES TO LIFE'S SMALL BEGINNINGS.
Scientists have the dullest of creation myths - no Adam made from lifeless dust, no Aphrodite born of foamy seas, just some conjectural watery womb where life began as a chemical accident.
But though drab as myth, the origin of life is supreme among scientific mysteries, and a notable stride now has been taken toward understanding the nature of what scientists call the universal ancestor, the living cell that lies at the root of the tree of evolution.
The new advance comes from analysis of a strange microbe that was recovered by the deep sea vessel Alvin from a volcanic vent on the Pacific floor. Here the microbe, known as Methanococcus jannaschii, lives at crushing pressures 245 times greater than at sea level and at scalding temperatures just a few degrees below the boiling point of water.
The microbe belongs to an ancient kingdom of organisms known as the archaea. Many live in extreme environments, like hot springs or deep sea vents. Despite their obscurity, the archaea constitute a third kingdom of life, alongside the prokarya, cells like bacteria that have no nucleus, and the eukarya, organisms with nucleated cells, which include all plants and animals.
The entire genome or genetic blueprint of the microbe has now been chemically sequenced by a team under J. Craig Venter at the Institute for Genomic Research in Gaithersburg, Md., and a report on the work is published in today's Science.
This is the first time the entire gene set of an archaean organism has been deciphered. Last year Venter's group cracked the full DNA sequence of the first bacterium and of a second microorganism called a mycoplasma. An international group of laboratories has finished, but not yet published, the full DNA sequence of yeast, a simple plant.
The sequencing of the Methanococcus DNA means that genetic blueprints are now or soon will be available for representatives of each of the three kingdoms of life. With three points of triangulation, scientists can start to work backward to figure out features of the universal ancestor cell of the three kingdoms.
The universal ancestor would have emerged after the beginning of life on Earth, at least 3.6 billion years ago, and before the branching into the three kingdoms some 3 billion years ago.
Venter says his data also put beyond doubt the question of whether the archaea are a separate kingdom. The idea was first proposed in 1977 by Carl R. Woese of the University of Illinois but received ``a universal thumbs down,'' Woese said at a news conference in Washington announcing the results Thursday.
The unusual nature of Methanococcus emerged from a comparison of its genes with those that have already been sequenced from other organisms, mostly prokaryotes or eukaryotes.
Venter said that he and his team, which included Woese, ``were astounded to find that two-thirds of the genes do not look like anything we've ever seen in biology before.''
From the genes that can be identified, it appears that Methanococcus has metabolic processes similar to those of bacteria but it has information processing genes more similar to those of eukaryotes.
The sequencing project was funded by a $1.1 million grant from the Department of Energy, whose Microbial Genome Project is the counterpart of the better known Human Genome Project, which the department runs jointly with the National Institutes of Health.
The Energy Department is interested in Methanococcus because the microbe's ability to synthesize methane from carbon dioxide and hydrogen could in principle contribute to some form of generating renewable energy.
Also, the many enzymes of Methanococcus that function at high temperatures may find a role in industrial processes. An enzyme from a similar deep ocean vent organism is already a vital ingredient in the DNA analysis technique known as the polymerase chain reaction.
Commercial rights to Methanococcus genes belong to Human Genome Sciences of Gaithersburg, Md., a company affiliated with the nonprofit Institute for Genomic Research.
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|Publication:||Daily News (Los Angeles, CA)|
|Date:||Aug 23, 1996|
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