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人工生命一步美科學家初步培育成「人造細胞」

作者:TCM  於 2010-5-21 12:04 發表於 最熱鬧的華人社交網路--貝殼村

通用分類:原創文學|已有4評論

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Scientists announced a bold step Thursday in the enduring quest to create artificial life. They've produced a living cell powered by manmade DNA. While such work can evoke images of Frankenstein-like scientific tinkering, it also is exciting hopes that it could eventually lead to new fuels, better ways to clean polluted water, faster vaccine production and more.

Is it really an artificial life form?

The inventors call it the world's first synthetic cell, although this initial step is more a re-creation of existing life — changing one simple type of bacterium into another — than a built-from-scratch kind.

Maryland genome-mapping pioneer J. Craig Venter said his team's project paves the way for the ultimate, much harder goal: designing organisms that work differently from the way nature intended for a wide range of uses. Already he's working with ExxonMobil in hopes of turning algae into fuel.

And the report, being published Friday in the journal Science, is triggering excitement in this growing field of synthetic biology.

"It's been a long time coming, and it was worth the wait," said Dr. George Church, a Harvard Medical School genetics professor. "It's a milestone that has potential practical applications."

The project has overcome some hurdles in engineering larger genomes that will help push forward the field, said biological engineer Dr. Ron Weiss, a Massachusetts Institute of Technology leader in synthetic biology.

"It's an important step," said Weiss. Even though the manmade DNA needed an already living cell to start working, eventually it reproduced and "all elements in the cells after some amount of time can be traced to this initial artificial DNA. That's a great accomplishment."

Scientists for years have moved single genes and even large chunks of DNA from one species to another. Venter aimed to go further. A few years ago, his team transplanted an entire natural genome, all of an organism's genes, one bacterium into another and watched it take over — turning a goat germ into a cattle germ.

Next, the researchers built from scratch another, smaller bacterium's genome, using off-the-shelf laboratory-made DNA fragments.

Friday's report combines those two achievements to test a big question: Could synthetic DNA really take over and drive a living cell? Somehow, it did.

"This is transforming life totally from one+ species into another by changing the software," said Venter, using a computer analogy to explain the DNA's role.

The researchers picked two species of Mycoplasma, simple germs that contain a single chromosome and lack the cell walls that form barriers in other bacteria. First, they chemically synthesized the genome of M. mycoides, that goat germ, twice as large as the germ genome they'd previously built.

Then they transplanted it into a living cell from a different Mycoplasma species, albeit a fairly close cousin.

At first, nothing happened. The team scrambled to find out why, creating a genetic version of a computer proofreading program to spell-check the DNA fragments they'd pieced together. The result: They found that a typo in the genetic code, in one of the synthetic genome's million chemical base pairs, was rendering the manmade DNA inactive, delaying the project three months to find and restore that bit.

"It shows you how accurate it has to be, one letter out of a million," Venter said.

That fixed, the transplant worked. The recipient cell started out with synthetic DNA and its original cytoplasm, but the new genome "booted up" that cell to start producing only proteins that normally would be found in the copied goat germ. It reproduced into a small colony of germs in a lab dish. The researchers had tagged the synthetic DNA to be able to tell it apart, and confirmed that those new ones really looked and behaved like M. mycoides, not the recipient cell


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回復 十三大爺 2010-5-21 12:19
Jim Watson once said about Craig Venter: Craig Venter does the type of experiments that can be done by a monkey.  Craig Venter is no scientist, his science is very poorly received by his peers, he is a maverick in science
回復 TCM 2010-5-21 12:46
十三大爺: Jim Watson once said about Craig Venter: Craig Venter does the type of experiments that can be done by a monkey.  Craig Venter is no scientist, his s
He was listed on Time Magazine's 2007 and 2008 Time 100 list of the most influential people in the world.
回復 十三大爺 2010-5-21 13:16
TCM: He was listed on Time Magazine's 2007 and 2008 Time 100 list of the most influential people in the world.
Maybe, but it doesn't change the fact that his science is poorly received in scientific community.  Why? being a maverick always chasing news talking points is not enough to make breakthroughs science.  Read this from New York Times.  I agree his work deserves to be published in Science though.

Some other scientists said that aside from assembling a large piece of DNA, Dr. Venter has not broken new ground. 「To my mind Craig has somewhat overplayed the importance of this,」 said David Baltimore, a geneticist at Caltech. He described the result as 「a technical tour de force,」 a matter of scale rather than a scientific breakthrough.

「He has not created life, only mimicked it,」 Dr. Baltimore said.

Dr. Venter』s approach 「is not necessarily on the path」 to produce useful microorganisms, said George Church, a genome researcher at Harvard Medical School. Leroy Hood, of the Institute for Systems Biology in Seattle, described Dr. Venter』s report as 「glitzy」 but said lower-level genes and networks had to be understood first before it would be worth trying to design whole organisms from scratch.

In 2002 Eckard Wimmer, of the State University of New York at Stony Brook, synthesized the genome of the polio virus. The genome constructed a live polio virus that infected and killed mice. Dr. Venter』s work on the bacterium is similar in principle, except that the polio virus genome is only 7,500 units in length, and the bacteria』s genome is more than 100 times longer.

Friends of the Earth, an environmental group, denounced the synthetic genome as 「dangerous new technology,」 saying that 「Mr. Venter should stop all further research until sufficient regulations are in place.」

The genome Dr. Venter synthesized is copied from a natural bacterium that infects goats. He said that before copying the DNA, he excised 14 genes likely to be pathogenic, so the new bacterium, even if it escaped, would be unlikely to cause goats harm.

Dr. Venter』s assertion that he has created a 「synthetic cell」 has alarmed people who think that means he has created a new life form or an artificial cell. 「Of course that』s not right — its ancestor is a biological life form,」 said Dr. Joyce of Scripps.

Dr. Venter copied the DNA from one species of bacteria and inserted it into another. The second bacteria made all the proteins and organelles in the so-called 「synthetic cell,」 by following the specifications implicit in the structure of the inserted DNA.

「My worry is that some people are going to draw the conclusion that they have created a new life form,」 said Jim Collins, a bioengineer at Boston University. 「What they have created is an organism with a synthesized natural genome. But it doesn』t represent the creation of life from scratch or the creation of a new life form,」 he said.
回復 cartoonyang 2010-5-21 17:11
It is amazing!!!

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