‘Radically rewritten’ bacterial genome unveiled

From Nature:

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Scientists continue to tinker with the Escherichia coli genome.

Synthetic biologists report the most far-reaching rewiring yet of a bacterial genome. The feat, described today in Science, involved repurposing 3.8% of the base pairs of the bacterium Escherichia coli1.

The scientists replaced 7 of its 64 genetic codons — sequences that code for amino acids — with others that produce the same components. They were able to reduce the number of codons by synthesizing the DNA in 55 fragments, each of which was 50,000 base pairs long. They have yet to reassemble those pieces into a functioning E. coli.

Despite that, the team, led by researchers at Harvard Medical School in Boston, Massachusetts, say that it is a major step in the push to engineer organisms with new properties, such as resistance to infection by viruses. The synthetic biologists, including George Church at Harvard, reported their results on 18 August in Science1. They say the work also serves as a prototype for the Human Genome Project—Write, in which scientists aim to synthesize a human genome.

“This is a demonstration that that kind of radical reengineering is feasible,” Church says.

“Going down from 64 to 57 codons is a dramatic departure from what exists in nature,” says Farren Isaacs, a synthetic biologist at Yale University in New Haven, Connecticut, who worked with Church on previous recoding studies but was not involved in this project. “It‘s an important step forward for demonstrating the malleability of the genetic code and how entirely new types of biological functions and properties can be extracted from organisms through genomes that have been recoded.”

Church’s lab and others have previously shown2 that it is possible to recode single amino acids in E. coli so that the bacterium can incorporate amino acids not found …

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