Except for the check-out-counter tabloids, the nearest thing yet to liveextraterrestrial beings meets the public today on the cover of Science.A press conference Thursday in Washington preceded this debut ofthe Archaea, now recognized as a third distinct domain of life onearth, alongside prokaryotes and eukaryotes.
Actually, these novel life forms are intraterrestrial; they inhabit ahigh-temperature, high-pressure world 2 miles down in volcanicvents, erupting from the ocean floor.
The microorganism presented to the press was known until lately asarcheobacteria. With its genome now fully sequenced, it joins theother two branches of life, not as a far-out bacterium, but as a coequalof prokaryotes, domain of one-celled invisible creatures, andeukaryotes, plants and animals _ including H. sapiens _ in whosecells, the nucleus comes wrapped in a membrane.
Today's Science introduces this microscopic E.T. with a ResearchNews editorial titled: "Life's last domain: With the genome of thearchaeon microbe Methanococcus jannaschi sequenced, researchersnow have genomes for life's three domains. And only 44 percent ofthe archaeon's genes are familiar."
The research report itself bears the heading, "Complete genomesequence of the methanogenic archaeon, Methanococcus jannaschii."
It took that paper's 40 co-authors just 13 months, from November1994 to December of last year, to decipher the weird bug's1,664,976-base-pair circular chromosome, plus two small extra-chromosomal elements totaling 74,957 base pairs. All told, M.jannaschii musters 1,738 protein-coding gene regions, withhomologies to both Prokaria and Eukaria. The authors have identifiedspecific roles for about 38 percent of them.
Of the 40 scientists who accomplished this feat of breakingArcharia's code, 35 are at The Institute for Genomic Research(TIGR) in Rockville, Md. Its president is J. Craig Venter, seniorauthor of the Science article, who chaired the standing-room-onlypress gathering.
"Archaea represent about 50 percent of the biomass on this planet,"Venter told his audience. "They are not necessarily seen, becausethey're tiny creatures."
M. jannaschii is named for microbiologist Holgar Jannesch of theWoods Hole Oceanographic Institution, which operates the deep-seasubmersible, Alvin. Jannesch told the meeting how, aboard Alvin,500 miles due south of Acapulco, Mexico, he had collected samplesof the Archeon microbe "from a `hot smoker' [thermal vent] 8,608feet below the surface of the Pacific Ocean. It lives at 245atmospheres of pressure, which would crush a conventionalsubmarine. That's a little over 3,700 psi, just to give you a sense ofthe incredible pressures these organisms are able to survive."
Extreme Conditions Shaped Archaeon's Lifestyle
He went on: "And at 185 degrees Fahrenheit [85oC] not much belowthe boiling point of water at sea level. They live without oxygen,without sunlight, without organic carbon as a energy source, and theyproduce methane."
Venter pointed out, "It's actually dangerous to grow this organism inthe lab, because it requires high pressure, and produces methane,which is explosive." He and his co-authors installed robots tomanipulate their material for TIGR's whole-genome randomsequencing technology. (See BioWorld Today, July 31, 1995, p. 1.)
"The robot prepares the clones," Venter told the assemblednewspeople. "It breaks the genome down into thousands of smallfragments, robotically isolated. We grow cultures of these to producemore DNA."
He continued: "Once we got the DNA from it, we determined thegenetic code. We can determine about 500 bases on each piece, andthen use massive computing to reassemble these 40,000 fragments."
The U.S. Department of Energy (DOE) provided TIGR with $3.3million to fund the genome-sequencing of M. jannaschii plus twoother archaeons, still in progress, and the prokaryote Mycobacteriumgenitalium. Venter and his colleagues completed the M. genitaliumproject, as well as Haemophilus influenzae's genome, last year.
DOE Deputy Secretary Charles Curtis told the conference: "We havea cleanup responsibility in the aftermath of the Cold War that hasbeen estimated to cost $225 billion or more. The potentialcontribution of these archaeons to that mission cannot beoverestimated."
Payoffs: Cleanup, Bioprocessing, Sustainable Fuel
Microbiologist D. Jay Grimes is program manager for DOE'sMicrobial Genome Program. He told BioWorld Today: "Within theMethanococcus there seem to be several genes that code for metal-binding proteins. These might be of use to the Department of Energy,in terms of cleanup of wastes, not only heavy metals butradionuclides. There are also," he added, "heat-stable enzymes thatcould be of use in bioprocessing to DOE and other interestedbodies."
He cited one biotech company, Recombinant Biocatalysis, of NewSharon, Pa., that is "looking at some of the archaea, trying to producecommercially useful enzymes for textile applications, chemicalsynthesis, food processing.
"And then, of course," Grimes observed, "we now have the completeset of instructions of an organism that makes methane, which ofcourse is a chemical feedstock and combustible energy source. As agreenhouse gas, it's also involved in global warming, with ozonechemistry. Its effect is to increase the concentration of ozone."
Grimes deems "entirely possible" the prospect of employing M.jannaschii to produce methane industrially. "It would certainly bedriven by economics and by fuel costs."
Venter pointed out in support of that prospect, "When methane getsburned, it breaks back down to carbon dioxide, and that's why peopleare worried about using it as a fuel. But here's an organism that canrecycle that CO2 back into methane as a renewable non-pollutingresource natural gas.
"TIGR's intellectual property rights," Venter said, "go to a publiclyheld company, Human Genome Sciences Inc. [of Rockville]. But theDOE also has some controlling rights over the exploitation of thiswork. Not so much its patentability," he added, "but that theinformation is going to lead to other discoveries that probably will bepatentable, which will lead to something useful."
Venter concluded: "If we're going to have bioelectric automobiles,it's not the genome patent that will get us there." n
-- David N. Leff Science Editor
(c) 1997 American Health Consultants. All rights reserved.