In a rare feat, scientists at the Scripps Research Institute have developed the first ever stable semisynthetic organism by aligning the DNA of natural and man-made bases.
The new life form that emerged in the California laboratory is neither fully organic nor artificial, but a hybrid of both. According to Floyd Romesberg, the researcher who led the project, the semi-synthetic organism is dependent on the man-made part to run its essential biology.
The SSO farming came as an extension of the team's 2014 study wherein they attempted the synthesis of a DNA base pair.
The study was published in the journal Proceedings of the National Academy of Sciences.
Pairing Of Synthetic Bases
Under the innovation, the new SSO would be using two synthetic bases X and Y paired in its genetic code besides the four natural bases of A, T, C and G common among all living organisms.
In the genome of living organisms, the natural bases A, T, C, and G are structured as two base pairs A-T and C-G on the DNA double helix.
The genetic code's base pairs make up the rungs of the DNA helix.
"We've made this semisynthetic organism more life-like," said Romesberg, senior author of the new study.
Romesberg and team inserted synthetic X and Y bases into the genetic code of single-celled bacteria. In the past attempt, they faced some challenges and now they are resolved and the unicellular organism can live with the synthetic base pair indefinitely and it keep dividing.
Romesberg and the team developed X and Y in 2014 and modified E. coli bacteria using that by incorporating the synthetic base pair in its genome.
But E. coli could not hold the base pair for long after the pair started dividing and dropped the X and Y base pair. That problem has been addressed by co-first authors of the study Yorke Zhang and Brian Lamb, who came up with a tool to optimize and strengthen the synthetic base pair. That worked well and the SSO was able to keep X and Y in its genome and the pair divided 60 times.
By making the SSO retain multiple synthetic base pairs, Rosemberg said, they can use "increased information in its DNA."
This will open up new frontiers in gene engineering and bioengineering, which alter the sequence of natural base pairs instead of incorporating synthetic ones.
"Protein drugs have revolutionized medicine, but their properties are limited by the limited properties of the natural 20 amino acids from which they are made," Romesberg said.
He said when proteins get more parts for specific purposes, making better drugs to treat different diseases will be easy.
The researchers are now planning to study how their new genetic code can be transcribed into RNA, which is the molecule that translates DNA into proteins.