Semi-synthetic bacteria
The semi-synthetic E. coli has a protein that allows it to glow green. Photo by Bill Kiosses for the Scripps Research Institute

Scientists at the Scripps Research Institute announced Wednesday they have created a strain of common E. coli bacteria with synthetic genetic components.

The DNA that is the basis of all life is made up of four chemical bases — adenine, cytosine, guanine and thymine, known by the letters A, C, G and T. Combinations of these four make up all the instructions for creating proteins in every organism.

What the Scripps scientists succeeded in doing is to create a strain of E. coli with two unnatural chemical bases, which they dubbed “X” and “Y,” in its DNA.

In a study published in the journal Nature, the researchers explained that their “semi-synthetic” strain of E. coli is the first to both contain the unnatural bases in its DNA and use the bases to instruct cells to make a new protein.

“I would not call this a new lifeform—but it’s the closest thing anyone has ever made,” said Scripps Professor Floyd Romesberg, who led the study. “This is the first time ever a cell has translated a protein using something other than G, C, A or T.”

The protein produced in this process was a variant of green fluorescent protein, a naturally glowing marker often used in genetic experiments, which contained different unnatural amino acids incorporated at a selected site.

“This was the smallest possible change we could make to the way life works—but it is the first ever,” said Romesberg.

With the addition of X and Y, an organism could code for up to 152 new amino acids. The researchers hope these amino acids could become building blocks for new medicines.

Chris Jennewein

Chris Jennewein is Editor & Publisher of Times of San Diego.