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Sunday, November 16, 2003

Artificial Life in a fortnight

Craig Venter is back in the news. This time for building a virus from scratch in two weeks, becoming the second virus to be synthesized artificially after Eckard Wimmer's polio virus in 2002 (which took 3 years to build and could barely infect a cell and reproduce).

Venter's team cobbled together the virus, called phi-X174, following its published genetic sequence. They stitched up its DNA from ready-made overlapping fragments called oligonucleotides, each built from 40 chemical building-blocks, or bases. The smart part, according to Wimmer, involved steps that eliminated genetic errors. For example, the team filtered out common oligonucleotides that harbour genetic mutations.

The team used enzymes to glue the oligonucleotides together accurately into the complete 5,386-base genetic strand, and to copy it many times. When the synthetic viral genome was injected into bacteria, the bacterial cell's machinery read the instructions and created fully fledged viruses. Genetically, one of the resulting virus strains was 100% identical to the natural virus, says Venter. By contrast, Wimmer's polioviruses, which were some 7,500 bases long, had to be laboriously checked for mistakes as each genetic piece was added.

Of course, the spectre of bio-terror (especially given the ease with which Dr. Venter's team built the virus) has been raised.

The study may revive concerns that such techniques could one day be hijacked to make pathogens such as polio or even smallpox for bioweapons. This was widely discussed following the publication of Wimmer's work. The prospect of synthetic viruses or bacteria also raises fears about their possible environmental impact. "It reminds us that we'll continue to confront these issues in an accelerating way," says public-health expert Stephen Morse of Columbia University, New York City. Now, as then, Morse and others argue that the benefits of the new technique outweigh the risks and that the method should be made public.

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