23-Jan-2017: Scientists create world’s first stable semi-synthetic organism.

Scientists at The Scripps Research Institute (TSRI) have announced the development of the first stable semisynthetic organism. Building on their 2014 study in which they synthesized a DNA base pair, the researchers created a new bacterium that uses the four natural bases (called A, T, C and G), which every living organism possesses, but that also holds as a pair two synthetic bases called X and Y in its genetic code.

While applications for this kind of organism are still far in the future, the researchers say the work could be used to create new functions for single-celled organisms that play important roles in drug discovery and much more.

During initial research in 2014,  these E. coli couldn't keep the base pair in their code indefinitely as they divided. The X and Y base pair was dropped over time, limiting the ways the organism could use the additional information possessed in their DNA. But, the new single-celled organism can hold on indefinitely to the synthetic base pair as it divides.

A New Use for CRISPR-Cas9

Finally, the researchers set up a "spell check" system for the organism using CRISPR-Cas9, an increasingly popular tool in human genome editing experiments. But instead of editing a genome, the researchers took advantage of CRISPR-Cas9's original role in bacteria.

The genetic tools in CRISPR-Cas9 (a DNA segment and an enzyme) originated in bacteria as a kind of immune response. When a bacterium encounters a threat, like a virus, it takes fragments of the invader genome and pastes them into its own genome -- a bit like posting a "wanted" poster on the off chance it sees the invader again. Later, it can use those pasted genes to direct an enzyme to attack if the invader returns.

Knowing this, the researchers designed the organism to see a genetic sequence without X and Y as a foreign invader. A cell that dropped X and Y would be marked for destruction, leaving the scientists with an organism that could hold on to the new bases. It was like the organism was immune to unnatural base pair loss. The semisynthetic organism was thus able to keep X and Y in its genome after dividing 60 times, leading the researchers to believe it can hold on to the base pair indefinitely.

This work is only in single cells and is not meant to be used in more complex organisms. The actual applications for this semisynthetic organism are "zero" at this point. So far, scientists can only get the organism to store genetic information.

Next, the researchers plan to study how their new genetic code can be transcribed into RNA, the molecule in cells needed to translate DNA into proteins. This study lays the foundation for what we want to do going forward.