NYTimes: Scientists Transplant Genome of Bacteria

六月 29, 2007


Published: June 29, 2007

Scientists at the institute directed by J. Craig Venter, a pioneer in sequencing the human genome, are reporting that they have successfully transplanted the genome of one species of bacteria into another, an achievement they see as a major step toward creating synthetic forms of life.

Other scientists who did not participate in the research praised the achievement, published yesterday on the Web site of the journal Science. But some expressed skepticism that it was as significant as Dr. Venter said.

His goal is to make cells that might take carbon dioxide out of the atmosphere and produce methane, used as a feedstock for other fuels. Such an achievement might reduce dependency on fossil fuels and strike a blow at global warming.

“We look forward to having the first fuels from synthetic biology certainly within the decade and possibly in half that time,” he said.

Richard Ebright, a molecular biologist at Rutgers University, said the transplantation technique, which leads to the transferred genome’s taking over the host cell, was “a landmark accomplishment.”

“It represents the complete reprogramming of an organism using only a chemical entity,” Dr. Ebright said.

Leroy Hood, a pioneer of the closely related field of systems biology, said Dr. Venter’s report was “a really marvelous kind of technical feat” but just one of a long series of steps required before synthetic chromosomes could be put to use in living cells.

“It’s a really worthy accomplishment, but I hope it doesn’t get hyped to be more than it is,” Dr. Hood said.

One reason for Dr. Venter’s optimism is that he says his institute is close to synthesizing from simple chemicals an entire genome, 580,000 DNA units in length, of a small bacterium, Mycoplasma genitalium. If that genome can be made to take over a bacterium using the method announced today, Dr. Venter should be able to claim that he has made the first synthetic life form. The bacterium would be identical to nature’s version, but would demonstrate how precise control could be achieved over every aspect of the machinery of living cells.

Biologists have long been able to move useful genes into bacteria and other organisms in a process called genetic engineering. The idea of synthetic biology is to carry out genetic engineering in a more extensive and systematic way.

Synthetic biologists, who held their third annual meeting in Zurich, Switzerland, this week, hope to create biochemical processes and then choose the gene sequences that will direct these processes and build the DNA from scratch. The scientists’ goal is to select and reorder the genetic machinery developed by evolution just as an engineer might assemble an efficient circuit board from existing components.

Dr. Venter hopes to lay the basis for a new approach to synthetic biology by first synthesizing whole genomes in the laboratory and then making them take control of, or “boot up,” a living cell. His new report accomplishes the second of the two steps, at least in Mycoplasma. His team, which includes a distinguished biologist, Hamilton Smith, purified the full DNA from one kind of Mycoplasma and showed that it could take control of another, making the host cell switch over to producing proteins specified by the inserted DNA. Dr. Smith said he was not sure whether the inserted genome destroyed the host genome or just made the cell divide, assigning the two genomes to different daughter cells.

Booting up cells with new genomes is a major limitation in synthetic biology, Dr. Venter said. With that hurdle now crossed, it will be possible to “design cells in future to manufacture new types of fuel and break our dependency on oil and do something about carbon dioxide going into the atmosphere.”

Dr. Hood, co-founder of the Institute for Systems Biology in Seattle, said the next step on Dr. Venter’s agenda, putting a functional synthetic genome into an organism, would be more significant.

“Synthesizing a whole chromosome and getting it to function will be a really remarkable step that will be much closer to the golden vision of creating new organisms,” he said.

The longest piece of DNA synthesized so far, he explained, is 35,000 units long, whereas the Mycoplasma genome or chromosome is 580,000 units.

The synthetic Mycoplasma, if the Venter team is successful, would be identical to the natural kind and should present no conceivable hazard. But synthetic biology is a technique with potentially far-reaching consequences like environmental effects and misappropriation by terrorists. In addition, the ability to synthesize living organisms may provoke philosophical comment.

Scientists have taken the initiative in assessing the effects with the hope of staying far enough ahead of events to avoid regulation. A report on the possible dangers of synthetic biology is being prepared for the Sloan Foundation by scientists at M.I.T., the Venter Institute and the Center for Strategic and International Studies.



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