Scientists at the Scripps Research Institute have successfully created the first living organism with an "alien" DNA which contains two extra bases, X and Y. Such a DNA has never occured in billions of years of evolution on Earth. In a normal DNA, which is present in every living organism on Earth, there are only two bases of double helix that are bonded together with four bases known as T (thymine), G (guanine), A (adenine) and C (cytosine).
The new semi-synthetic alien organism has continued to reproduce normally while preserving the new alien DNA during reproduction. The research could lead to creation of highly customized organisms in future such as bacteria, animals, and even humans which could behave in a weird and wonderful ways that the already existing DNA doesn't allow.
The research has been 15 years in the making where the scientists have created the semi-synthetic organism with an expanded genetic alphabet. The addition of new letters could enable biologists to vastly expand the range of proteins that they could synthesize. “What we have now is a living cell that literally stores increased genetic information,” says Floyd Romesberg, a chemical biologist at the Scripps Research Institute in La Jolla, California, who led the 15-year effort.
The research team engineered a bacterium known as Escherichia coli to express a gene from a diatom which is a single-celled alga encoding a protein that allowed the molecules to pass through the bacterium's membrane. The scientists then created a short loop of DNA called a plasmid, containing a single pair of the foreign bases, and inserted the whole thing into E. coli cells. With the diatom protein supplying a diet of foreign nucleotides, the plasmid was copied and passed on to dividing E. coli cells for nearly a week. When the supply of foreign nucleotides ran out, the bacteria replaced the foreign bases with natural ones.
The alien E. coli contains just a single pair of foreign DNA bases out of millions. But Benner sees no reason why a fully alien cell isn’t possible. “I don’t think there’s any limit,” he says. “If you go back and rerun evolution for four billion years, you could come up with a different genetic system.” Potential uses of the technology could also include the incorporation of a toxic amino acid into a protein to ensure that it kills only cancer cells. This would make cancer treatment ever more advanced and effective.
It is possible that these scientists might be able to create a complete synthetic organism which could be unrecognizable. These organisms could be potentially capable of doing whatever these scientists want them to.
For now, the researchers are still trying to figure out how long the bacteria can survive and are also trying to see if its possible to produce a strain with more than one X-Y pair. The newly created organism won't be able to survive outside unless it is reverted back to the traditional four-letter DNA alphabet, as it needs to feed on synthetic molecules (that only the scientists can supply) to replicate. So according to the scientists, the organism would never infect other organisms in its current form in case it escapes from the lab because it would most likely die.