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Researchers for the first time created microbes containing artificial DNA, expanding the universal genetic code that guides life. The advance one day could lead to new antibiotics, vaccines and other medical products not possible with today's bioscience.

In a report published Wednesday in Nature, the scientists said they created two additions to the normal genetic code, and then prompted bacteria to incorporate these pieces of man-made DNA with few ill effects.

"The cells recognized it as natural," said chemical biologist Floyd Romesberg at the Scripps Research Institute in La Jolla, Calif., who led the research group.

The experiment demonstrates the feasibility of life-forms based on a different DNA code, independent experts said. Eventually, scientists could use an expanded genetic code to design living cells that could make new medical compounds.

By one recent estimate, the market for biologic and protein-based therapies is expected to reach $165 billion a year by 2018.

"Most people thought this wasn't possible," said biochemist Steven Benner at the Foundation for Applied Molecular Evolution in Gainesville, Fla., who wasn't involved in the project. Many scientists assumed that a normal cell would ignore any imitation DNA. "He has gone inside a cell and gotten it to work and that is a shock," said Dr. Benner.

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