Replacing a Genome Boosts Race to Develop Designer Bugs

Dr. J. Craig Venter, head of the Institute for Biological Energy Alternatives

Researchers have transformed one bacterial species into another by swapping their genomes, a move that will accelerate the race to develop custom-built synthetic bugs, a pioneer on genetics has said.

Craig Venter, who had a hand in mapping the human genome, said Thursday that a team of his researchers had transplanted the entire genetic code of one bacterial organism into another closely related species.

The experiment marks the most ambitious attempt yet to re-engineer a living cell with a view to one day developing microorganisms that could be used for biofuels, cleaning up toxic waste, sequestering carbon or other applications.

For decades, molecular biologists have genetically modified microbes and other kinds of cells by adding short DNA sequences, whole genes and even large pieces of chromosomes in their quest to fashion synthetic bugs that can make anti-malaria drugs or novel biofuels.

But this is the first time that researchers have transplanted an entire genome into a living organism and shown that the cell can express the foreign DNA.

The experiment shows for the first time that it is possible to insert an intact genome into a host organism and have that organism express the foreign DNA. The next step is to create a synthetic genome and transplant that into a host organism.

The researchers took the genome of a simple, one-celled organism called Mycoplasma mycoides and transplanted it into a close relative, M. capricolum.

Both of these bacteria, which are innocuous goat pathogens, lack an outer membrane, facilitating genome transfer.

Before transplantation, the researchers modified the DNA of the donor bacteria, adding two genes that would provide proof if the transfer had worked. One gene conferred antibiotic resistance, the other caused bacteria expressing it to turn blue.

The enhanced Mycoplasma mycoides genome was added to a test-tube of M. capricolum, and the contents of the tube were exposed to an antibiotic.

Within four days blue colonies appeared, indicating that the host organisms had taken up the foreign DNA.

When the team analyzed the blue bacteria for DNA sequences specific to either mycoplasma, it found no evidence of the host bacteria's genetic material.

Many questions still remain. The researchers acknowledged that they were not sure how the one genome displaced the other.

Source: AFP

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