On Jan. 23, 2017, scientists at The Scripps Research Institute (TSRI) announced the development of the first stable semisynthetic organism. The researchers, building on their 2014 study in which they synthesized a DNA base pair, created a new bacterium that uses the four natural bases (i.e. 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, and can hold on indefinitely to the synthetic base pair as it divides.

TSRI Professor Floyd Romesberg and his colleagues have now shown that their single-celled organism can hold on indefinitely to the synthetic base pair as it divides. Their research was published in the journal Proceedings of the National Academy of Sciences.

When Romesberg and his colleagues announced the development of X and Y in 2014, they also showed that modified E. coli bacteria could hold this synthetic base pair in their genetic code. What these E. coli couldn’t do, however, was 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.