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Synthetic viruses just around the corner

Advances in DNA technology may soon allow us to make organisms to order -- for good or ill.

Mycoplasma genitalium: can make do with just 200 of its 500 genes

Researchers believe that we are only a few years away from being able to synthesize viruses from their chemical building blocks. And, in the more distant future, it may be possible to construct entire cells. The ramifications of such work range from better vaccines, to resurrecting extinct organisms, to devising deadlier and more selective biological weapons.

Many viral genomes, including HIV, have fewer than 10,000 DNA bases -- the letters in the genetic code. The biggest DNA molecule synthesized to date is just under 3,000 bases long. But Clyde Hutchinson, of The Institute for Genomic Research, Rockville, Maryland, told the annual meeting of the American Association for the Advancement of Science (AAAS) in San Francisco that the extension of this into the viral range is "imminent".

Most biologists do not count viruses as living entities, as they cannot function independently of their host cells. No one is sure of the size of the smallest genome that could accomplish this.

Hutchinson studies the bacterium Mycoplasma genitalium which, at 600,000 DNA bases, has the smallest known genome (humans have 3 billion). His team is trying to work out which of the bugs' genes can be knocked out without killing it.

His results so far suggest that M. genitalium can manage without about 200 of its 500 genes -- at least if they are disabled one at a time. But the differing functions of essential and superfluous genes are still unknown.

Armed with knowledge of the smallest genetic toolkit necessary for life, it may be possible to concoct designer microbes to produce drugs or suck up toxins from polluted sites. "But that is a long way off," commented Hutchinson.

Also, he said, in a world with synthetic genomes and cells, "extinction isn't forever anymore". But one possibility is that, instead of trying to resurrect the dodo, future military biotechnologists might be more interested in recreating pathogens such as the smallpox virus -- or devising diseases targeted at, for example, specific ethnic groups.

Whether such weapons are possible is debatable, at least with our current knowledge. Race is as much a cultural phenomenon as a biological one -- the human genome shows that there is more genetic variation within racial groups than between them. So the chances of finding a trait universal within an ethnic group yet limited to it, and which could be used to target a bioweapon, seem remote.

But, comments bioethicist Jonathan Mereno of the University of Virginia, Charlottesville, "we can predict that attempts will be made to develop such weapons" -- probably involving experiments on human subjects.

The apartheid regime in South Africa is believed to have tried to make biological weapons that would select victims according to skin colour, Mereno told the meeting. And many other governments are researching the issue, with a view to gauging these weapons' feasibility and what might be done to counteract them.

It is illegal under international law to try and develop an ethnically targeted bioweapon. But at the moment, Mereno warned, "the apparatus to enforce the regulation isn't there".


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Whitfield, J. Synthetic viruses just around the corner. Nature (2001).

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