Thursday, July 14, 2011

E. Coli’s genetic code

Biologists report hijacking E. Coli’s genetic code
By Nicholas Wade
New York Times
July 14, 2011

Synthetic biology, the quest to hijack living systems and convert them to human-directed goals, is on the march. Last year biologists synthesized the entire genome of a small bacterium and showed how it could successfully infect a second bacterium. Now, in what may be a more significant advance, biologists have shown they can radically change a genome, not just copy it.

A team led by Farren J. Isaacs and George M. Church of the Harvard Medical School has devised a method for making hundreds of changes in a genome simultaneously. This massively parallel intervention, as the changes are known, is one of the advances that would be needed in another project Dr. Church and others have contemplated, that of recreating the mammoth by starting with an elephant’s genome and changing it at the 400,000 sites at which elephant DNA differs from that of the mammoth.

In the present instance, Dr. Isaacs and Dr. Church have been working not with a mammoth but with the standard laboratory bacterium known as E. coli. To prove they can seize control of the microbe’s genetic code and reprogram it, they have focused on one of the code’s 64 elements, known as the amber stop codon.

In Thursday’s issue of the journal Science, they report they will soon be able to delete the amber stop codon from all 314 sites in which it occurs in the E. coli genome, without harm to the organism. The codon can then be reinserted, but with a new function, like introducing a novel chemical unit into the bacterium’s proteins.

Genetic engineers have become adept at changing one gene in a genome, but it is quite another thing to alter a genome at 314 sites simultaneously.

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