Craig Venter, the controversial biologist who led the private effort to map the human genome, has moved closer to his goal of creating the first artificial life form by replacing the entire genetic code of one microbe with that of another.

The groundbreaking experiment has in effect turned a bacterium into a different species by substituting its DNA with that of a close relative. The success opens the way for doing the same thing with a genome that has been man-made from scratch, to create synthetic life.

Dr Venter has long been researching ways to make artificial organisms, with a view to creating new species of bacteria that produce environmentally friendly fuels such as hydrogen. This month he was said to have applied for a patent on a DNA sequence described as the “minimal genome” – the bare essential genes that can support life.

His team’s achievement takes him much closer to his goal, as the genome-swapping technique could be used to insert a DNA sequence that he has built into the shell of an existing bacterium. Whereas the cell’s membrane would be natural, its software – the genetic code containing the instructions for life – would be wholly artificial. “It’s like changing a Macintosh computer into a PC by inserting a new piece of software,” Dr Venter said.

The research could lead to new methods of genetic engineering in larger organisms, potentially including humans. The technique could allow scientists to create and insert artificial chromosomes carrying added genes into the genome, though many years of research would be required.

In the new experiment, which is published in the journal Science, researchers from the J. Craig Venter Institute in Rockville, Maryland, first extracted DNA from the donor bacterium species – Mycoplasma mycoides. This was then inserted into the host bacterium, a close relative known as Mycoplasma capricolum.

When bacterial cells were tested after the DNA transplant, they were using only the added genome, and had become biologically identical to the donor bacteria. The host cells’ genomes had been silenced or destroyed.

“We don’t know for certain how the donor genome takes over,” Dr Venter said. “But what is clear is that the technique works.”

The work will raise fresh controversy over the ethics of creating man-made life forms, and the hazards that it might pose. The project has drawn criticism from groups concerned that it is unethical to patent new forms of life, and those worried that similar techniques could be used to create dangerous new germs.

Dr Venter, however, said that his team had worked under ethical scrutiny at every stage, and even interrupted the project for 18 months while a bioethics panel was convened to review it.

“I don’t think there has ever been another field of science that has had so much public input and analysis before there have been any results,” he said. “Potential abuses such as biological warfare concern everyone in the field.”

Independent scientists said that the work was a significant step towards the creation of artificial life. Brian Spratt, professor of molecular microbiology at Imperial College, London, said: “Craig Venter has been promising a synthetic bacterium for some time. He appears to have solved one of the two key steps – a proven mechanism by which he could replace the resident chromosome of a bacterium with a chromosome synthesised in a test tube. Now he has to show he is able to produce the synthetic chromosome. I think most people who know Craig believe he will make a synthetic bacterium.”

Times Recommends

• Phoebe Caldwell wins Times/Sternberg Award
• Raging against fake pop has its own pitfalls
• How a voice for everyone led to stalemate