A computer-generated representation of a strand of DNA.

Scientists have created the first cell controlled by a human-made genome — a step closer to artificial life that is drawing both praise and warnings of potential dire consequences.

A team from the J. Craig Venter Institute in Rockville, Md., announced on Thursday it had created a synthetic bacterial genome that is a copy of an existing genome. The scientists then transplanted the synthetic genome into a different bacterium cell to create what they call a synthetic cell, although technically only its genome is synthetic.

The new genome then "booted up" the recipient bacterium's cell in much the same way that a computer's operating system makes the computer work.

The scientists say the eventual goal is to build new organisms that act in ways that differ from what nature intended, such as custom-made bacteria designed for biofuel production or environmental cleanup.

Work took 15 years

The study was published online Thursday in the peer-reviewed journal Science. It represents the result of 15 years worth of work by 20 scientists at a cost of about $40 million US.

"It's exciting for the scientific, technological and engineering prowess involved," said Christian Burks, president of the Ontario Genomics Institute, one of six regional genome centres in Canada. "The door that is meant to be opened here is the notion of harnessing a whole organism that can be customized to be good at doing something we want it to do."

J. Craig Venter, the institute's founder and a leading scientist in synthetic biology, told reporters in Washington that the bacterium is the first self-replicating species "whose parent is the computer."

"This is the first synthetic cell that's been made, and we call it synthetic because the cell is totally derived from a synthetic chromosome, made with four bottles of chemicals on a chemical synthesizer, starting with information in a computer," he said.

"This becomes a very powerful tool for trying to design what we want biology to do. We have a wide range of applications [in mind]."

Specific examples include designing algae to capture carbon dioxide and make new hydrocarbons that could go into refineries, or speeding up vaccine production.

Critics weigh in

But the idea of releasing such genetically-engineered organisms into the environment scares some observers.

"We're talking about a self-replicating organism. We know living pollution can't be controlled. It can't be recalled," said Lucy Sharratt, co-ordinator of the Canadian Biotechnology Action Network, a coalition of 17 agricultural and environmental organizations.

"We can't predict the consequences. Venter's perspective that organisms can be built like Lego misses all of the dangerous questions about how life works."

Catholic Church officials have also weighed in on Venter's most recent work, saying it could be a positive development if correctly used, but warned scientists that only God can create life.

"It's a great scientific discovery. Now we have to understand how it will be implemented in the future," said Monsignor Rino Fisichella, the Vatican's top bioethics official.

"If we ascertain that it is for the good of all, of the environment and man … we'll keep the same judgment," he said. "If, on the other hand, the use of this discovery should turn against the dignity of and respect for human life, then our judgment would change."

Entire genome transplanted

While scientists have been able to transplant genes from one species to another for several years now, the Venter team transplanted an entire synthetic genome to one bacterium from another.

The scientists synthesized the genome of a type of bacteria called Mycoplasma mycoides and transplanted it into a related species of bacteria called Mycoplasma capricolum.

"Once the new chromosome is in that recipient cell, all the traces of that recipient species disappear within a few rounds of replication," Venter told Science.

The transplantation was not a straightforward operation, because current technology only allows scientists to assemble relatively short strings of DNA letters at a time.

Engineered genome

To get around this problem, the Venter team inserted the shorter sequences they had created into yeast, whose DNA-repair enzymes linked the strings. They then transferred the medium-sized strings into E. coli and back into yeast. After three rounds of assembly, the researchers had produced a genome over a million base pairs long.

Venter said he is confident his team can keep the engineered genome in the lab because neither species of bacteria grow independently. Mycoplasma mycoides exists in goats, and sometimes cattle, and can cause mastitis, or inflammation of breast tissue.

"We have not tested to see whether this would still grow in goats. Unless a goat walks into the laboratory, or somebody walks out of our laboratory and injects a goat, we're probably pretty good with containment," Venter said, stressing that his institute has sought and received ethical reviews of its research.

With files from The Associated Press