Scientists Report DNA Transplant

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The organisms he is working with do not cause disease, he said, and could be modified so they cannot survive outside the laboratory.

The DNA transplants involve chemical washes that gently clean the donor DNA, and other washes that make the recipient's outer membrane porous, so the new DNA can enter.

It usually fails. But in about one of every 150,000 tries, the new DNA moves in, turns on, and, for reasons that remain unclear, the old DNA disappears.

Barbara Jasny, a senior editor at Science, called the work "a landmark in biological engineering."

Kevin Eggan, of the Harvard Stem Cell Institute, offered a more tempered assessment. He said the very simple cells Venter chose to work with, called mycoplasmas, are not representative of the kinds of cells most biologists believe will be useful in synthetic biology.

And, he said, although Venter's team has had some success, "They don't really understand how it works" -- a criticism that Venter acknowledged as true.

George Church, a Harvard professor of genetics and founder of a competing synthetic biology company, Codon Devices of Cambridge, Mass., said he was impressed by the mega-base size of the transplant. But he said a lot needs to be learned about why most transplants do not work and how the recipient's DNA is shut down.

"There are a lot of missing dot-dot-dots," he said.

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