Scientists Create "Synthetic Cell"
Thursday, May 20, 2010
Scientists say they've made a huge advance in their quest to create artificial life. They've produced a living cell powered by manmade DNA.
While such work can invoke 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.
But 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.
"This is the first self-replicating species we've had on the planet whose parent is a computer," Venter told reporters.
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."
Scientists for years have moved single genes and even large chunks of DNA from one species to another. At his J. Craig Venter Institute in Rockville, Md., and San Diego, Venter's team aimed to go further. A few years ago, the researchers transplanted an entire natural genome — the genetic code — of 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 a simple germ named Mycoplasma. First, they chemically synthesized the genome of M. mycoides, that goat germ, which with 1.1 million "letters" of DNA was 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. They found that a typo in the genetic code 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. The researchers had tagged the synthetic DNA to be able to tell it apart, and checked as the modified cell reproduced to confirm that new cells really looked and behaved like M. mycoides.
"All elements in the cells after some amount of time can be traced to this initial artificial DNA. That's a great accomplishment," said biological engineer Ron Weiss of the Massachusetts Institute of Technology.
Even while praising the accomplishment — "biomolecular engineering of the highest order," declared David Deamer of the University of California, Santa Cruz — many specialists say the work hasn't yet crossed the line of truly creating new life from scratch.
It's partially synthetic, some said, because Venter's team had to stick the manmade genetic code inside a living cell from a related species. That cell was more than just a container; it also contained its own cytoplasm — the liquid part.
In other words, the synthetic part was "running on the 'hardware' of the modern cell," University of Southern Denmark physics professor Steen Rasmussen wrote in the journal Nature, which on Thursday released essays of both praise and caution from eight leaders in the field.
The environmental group Friends of the Earth said the new work took "genetic engineering to an extreme new level" and urged that Venter stop until government regulations are put in place to protect against these kind of engineered microbes escaping into the environment.
Venter said he removed 14 genes thought to make the germ dangerous to goats before doing the work, and had briefed government officials about the work over the course of several years — acknowledging that someone potentially could use this emerging field for harm instead of good.
But MIT's Weiss said it would be far easier to use existing technologies to make bioweapons: "There's a big gap between science fiction and what your imagination can do and the reality in research labs."
Venter founded Synthetic Genomics Inc., a privately held company that funded the work, and his research institute has filed patents on it.