Scientists add two new letters to DNA's 'alphabet'

Using bacterial cells, scientists have managed to create a 'semi-synthetic organism' whose DNA has six 'letters,' instead of the usual four.

Researchers say that they have successfully incorporated synthetic DNA bases within the genetic material of E. coli cells, and had the cells copy the artificial base pair in their DNA.

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Floyd Romesberg, Associate Professor of Chemistry at the Scripps Research Institute in California and an author of the study published in thejournal Nature says that he and his team have managed to create a "semi-synthetic organism" by integrating the artificially synthesized base pair "into the machinery of life" where thesemi-synthetic component functions alongside the natural components..

First, the team had to engineer base pairs that could be recognized by DNA polymerase, a natural enzyme that replicates DNA. After examining some 300 different analogues, in 2009, researchers zeroed in on two molecules known as d5SICS and dNaM after they observed that in a test tube, these molecules worked very well with DNA polymerase.

After figuring out which molecules would be compatible with the enzyme, the team then attempted to introduce these into a living cell.

What they needed was a "transporter" that could effectively deliver the components one at a time into the cell. "We borrowed the triphosphate transporter from a species of microalgae," says Romesberg.

That was a big breakthrough for us an enabling breakthrough, said Denis A. Malyshev, a member of the Romesberg laboratory who was lead author of the paper, in a press release.

After the tools were in place, the team got down to the actual process of introducing the components into the bacterium.

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Scientists add two new letters to DNA's 'alphabet'