Biologists have converted one species of bacterium into another by replacing all of its DNA, a critical step toward their ultimate goal of designing entire organisms from scratch, according to a study published Thursday.
The transplanted DNA took over its single-cell host in about three days. The resulting bacterium was indistinguishable from the donor species, the researchers reported in the online edition of the journal Science.
"This is the equivalent of changing a Macintosh computer to a PC by inserting a new piece of software," said J. Craig Venter, a maverick geneticist and senior author of the study.
Venter's team intends soon to apply the technique to a string of genes assembled in a laboratory and bring to life a simple creature that has never existed before.
Eventually the scientists hope to create tiny genetic factories for churning out environmentally friendly fuels and chewing up unwanted carbon dioxide.
In the burgeoning field of synthetic biology, "this is an important development," said bioengineer Jay D. Keasling of UC Berkeley and the Lawrence Berkeley National Laboratory.
With this tool in hand, "anybody should be able to construct bacterial cells from scratch," said Drew Endy, a biological engineer at MIT.
Venter, who famously challenged the decade-long effort by federal scientists to decode the human genome by completing the feat at a private company in just two years, said the DNA transplants had so far worked only in two closely related bacterium species.
He and his colleagues at the J. Craig Venter Institute in Rockville, Md., cautioned that it would take time to figure out the recipes for transferring genomes between other organisms.
In the study, the researchers removed intact DNA from \o7Mycoplasma mycoides \f7and inserted it into \o7Mycoplasma capricolum\f7. Both bacteria cause respiratory disease and other ailments in goats. They were chosen for the experiments because they have relatively small genomes and grow rapidly, allowing scientists to gather data in a matter of days.
The team inserted a gene for resistance to the antibiotic tetracycline into the donor bacterium before removing its DNA. They then mixed the naked DNA with the host bacterium and exposed it to tetracycline, which killed off any bacteria that lacked the antibiotic-resistance gene. After a few days, the surviving organisms contained only the donor DNA.
