Scientists working in the new field of synthetic biology have yielded to public pressure and deferred adopting a self-regulating code of conduct. Synthetic biology, which aims to engineer cells to make useful devices, is highly controversial because of its potential for creating bioweapons and environmental risks. A conference in Berkeley, California, last week featured a draft of guidelines for self-regulation. However, on the eve of the meeting, 35 groups, including Greenpeace International and GeneWatch UK issued a counterproposal calling on scientists to participate in public debate. "Scientists creating new life forms cannot be allowed to act as judge and jury," said Sue Mayer, director of GeneWatch.

Like other exciting new fields, synthetic biologists wax lyrical about the payoff from creating organisms which have been programmed at a genetic level. The benefits for medicine, agriculture, manufacturing and energy production could be huge. But what alarms many people is the possibility of bioterrorism. Theoretically, for instance, it would be possible to piece together the lethal smallpox virus. Even Scientific American has urged biotechnologists to be cautious. "Half a century ago, if recklessness, greed and unreasonable fear had somehow handicapped the development of integrated circuits, then the computing and communications revolution would have been snuffed out. Now is an equally pivotal moment for the future of biotechnology," said an editorial.