In the May 15, 2014, edition of the journal Nature, Floyd Romesberg’s chemistry lab at San Diego’s Scripps Research Institute published a paper titled “A Semi-Synthetic Organism with an Expanded Genetic Alphabet.” Romesberg and his colleagues had created a bacterium incorporating chemical building blocks that, as far as anybody knows, have never been part of any earthly life form.
There had been previous claims to “creating life.” Genome pioneer Craig Venter led a team that manufactured a genome for a germ that causes pneumonia in cows, but their effort used the familiar chemical bases of DNA, known by the letters A, G, C, and T. Romesberg’s group, on the other hand, added two additional letters, dubbed X and Y. When the bacteria successfully replicated X and Y in succeeding generations, Romesberg’s lab could claim to have made the first living thing with an expanded genetic code.