A Trinity in the Tree of Life
Fourteen years ago, the diving vessel Alvin plucked a bizarre, single-cell creature from a volcanic vent 1,000 miles off the coast of Baja California. There, under crushing pressures 245 times greater than at sea level and at temperatures just a few degrees below the boiling point of water, the Methanococcus jannaschii and its ancestors had thrived for up to 3 billion years.
Until recently, scientists thought of the creature, which resembles a microscopic squid several hundred times smaller than the period at the end of this sentence, as a kind of oddball bacterium. But in the Aug. 23 issue of the journal Science, a team of researchers led by J. Craig Venter of the Institute for Genomic Research argues that this hardy creature and others like it actually make up the Archaea, a third branch (or “kingdom”) on the tree of life. (The other two kingdoms are the Prokarya, cells like bacteria wherein DNA floats freely, and the Eukarya, organisms like plants and animals that contain their DNA in a nucleus.)
Though the Methanococcus also has free-floating DNA, its genetic differences are dramatic enough to give it a kingdom of its own. Researchers have only now had computers powerful enough to analyze its 1,739,933 chemical units of DNA. Two-thirds of its genes, says Venter, “are completely different than anything else ever seen before. They are totally new to science.”
The discovery has some immediate implications. First, it shows how new fields like biotechnology have forged a healthy symbiosis between government and private industry. Private industry pioneered the supercomputers that Venter’s researchers required, while $1.1 million in federal funding provided time and facilities. Now, the government’s investment in research once considered highly theoretical stands to produce some practical payoffs.
The creature’s ability to recycle natural methane, for instance, could perhaps be harnessed to generate renewable energy for cars and homes. And its forte, digesting heavy metals and converting them into other compounds, may help clean up spoiled environments.
What is arguably most valuable about Venter’s discovery, however, is its reminder that human life is but one of many quirky variations on earthly life. Scientists now say that up to 20% of Earth’s biomass, the space taken up by living things, may be occupied by the Methanococcus and its Archaean relatives. They thrive in the many sweltering, crushing and highly acidic parts of the planet, mostly in oceans, that once were thought inimical to life.
Reflecting the scientific confidence of her era, the philosopher Hannah Arendt wrote in 1958 that “the earth is the very quintessence of the human condition.” But more realistic, perhaps, is this humble benediction from 19th-century novelist Thomas Hardy: “Let me enjoy the earth no less / Because the all-enacting Might / That fashioned forth its loveliness / Had aims other than my delight.”
