While you were on your summer vacation, scientists announced the decoding of the genetic structure of the first member of the Archaea (the ancient microorganism that seem to form the trunk of life's evolutionary tree). The microbe, Methanococcus jannaschii, ordinarily lives -- not that you can call it much of a living -- near a deep-sea vent at the ocean floor, at 245 times atmospheric pressure, and at nearly 100 C. The complete genetic code for the microbe was published in the 8/23/96 issue of Science magazine by a team led by J. Craig Venter of the Institute for Genomic Research in Gaithersburg, Md. Last year, Venter led a group that unraveled the first bacterial sequence in history. (Here's information about the recent sequencing of Mycoplasma genitalium, a bacterium that causes genital infections.) So what? The two bacteria that were sequenced previously contained few surprises, Woese says, since so much was known about the genetics of their relatives. In contrast, the structure of the 1700-odd genes in the archaeon (member of the kingdom Archaea) have surprised scientists, since two-thirds of them have never been seen before. But they reinforced his view that Archaea are more closely related to Eukarya (the kingdom including all cells with nuclei) than to bacteria. According to the sequencing of genetic material, this is the structure of life. Notice what a tiny fraction of the whole picture is occupied by plants and animals. Courtesy of Carl Woese. You didn't have much of a bank of Archaea genes that had been functionally characterized or identified," says Woese. "The impressive thing was that of the new ones that uncovered, most of these did not have recognizable counterparts in the databases from other organisms. These genes are going to be a shopping list for biochemists" looking for enzymes with specific properties. After the expected publication of the first sequence of a fungus, scientists will be in a position to probe the relationship among Archaea, bacteria, and eukarya kingdoms. Thus the real import of sequencing Methanococcus jannaschii is not what it tells about the particular organism, Woese says, but what it tells us about the methane-producing Archaea. "This [degree of difference] alerts people about what it really means to say that something is from another kingdom -- domain -- of life." See "Scientists Discover a Clue..." and "Complete Genome Sequence" in the bibliography.

		Update 1998. The pretty picture we've shown you turns out to be a simplification of reality. Now that the complete genomes of more than a dozen microbes are known, it seems that Eukarya -- the higher organisms -- may not have sprouted off the Archaea, as Woese supposed. Genetic information from organisms on the three branches of life seem contradictory at this point. As Woese said The New York Times, "Each picture is different, so there's tremendous confusion." The problem could be rooted in the ability of organisms like bacteria to transfer groups of genes among themselves, or even to engulf other organisms and incorporate their genes. That kind of transfer would make a tree metaphor, with everything tracing back to a common ancestor, less appropriate than a network metaphor, with myriad connections between what we've been calling branches on the tree of life. (See "Tree of Life Turns Out..." and "Genome Data Shake Tree..." in the bibliography)

. A last word If you've been awaiting the pitch to conserve Earth's species -- bizarre or benign -- then you've read far enough. Good planets are hard to find, and as far as we know, Mars has been dead for quite a while. So take care of your planet. Want to read how species are being returned to their historic homes on Earth? Then click this clicker. Still not feeling insignificant enough? Then why not check out our bibliography...

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