The creation of artificial life is only a step away after the controversial biologist Craig Venter announced yesterday that his team had successfully synthesised the entire genetic code of a bacterium.

By piecing together the 582,970 DNA letters of Mycoplasma genitalium from scratch, Dr Venter has completed the second of three stages required to produce a man-made organism.

Last year his J. Craig Venter Institute in Rockville, Maryland, made the first move towards this ambitious goal by transforming one microbe into another by substituting its DNA with that of a close relative. The final step will now be to use this genome transplant procedure to place the newly built artificial chromosome into a bacterial cell. This will create a life form with biological instructions written entirely by humans.

Efforts to achieve this have already begun, and the team hopes for success within months. Dr Venter, who courted controversy with his project to sequence the human genome for profit, wants to create artificial organisms so that he can synthesise new species of bacteria that produce environmentally friendly fuels such as hydrogen.

He has commissioned independent bioethicists to review his project. Critics have raised concerns that the technology could either deliberately or accidentally produce virulent new germs.

In a study published in the journal Science, a team led by Daniel Gibson and Hamilton Smith made fragments of DNA from its chemical ingredients. These were then grown inside yeast cells to assemble them in the order of the genome of M. genitalium, which is so called as it was first found living in the urethra. Its genome contains 18 times more DNA letters than the next biggest that has been built in the laboratory.

“We have completely synthesised a chromosome, and we can now try to boot it up in a cell,” Dr Venter said. “There are still barriers to this – it’s not a slam dunk, or we’d be announcing it today. But we are confident they can be overcome.”

To create the first artificial microbe, which the scientists are calling Mycoplasma labatorium, the synthetic genome will be inserted into a related species of bacterium that will serve as a host. Previous experiments have shown that doing this cancels the genetic code of the host cells and replaces it with the added genome.

The first synthetic life form will have an almost identical genetic code to the natural version of M. genitalium, but its DNA will have come “from chemicals in bottles”, Dr Venter said. It would also contain extra bits of nonfunctioning DNA added to assist the assembly process.

In the longer term Dr Venter plans to use the same technique to design genomes with specific purposes in mind that would be inserted into host cells to make entirely new microbes.

Dr Smith, who won the Nobel Prize for Physiology or Medicine in 1978, said: “We have shown that building large genomes is now feasible and scalable so that important applications such as biofuels can be developed.”

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