A new step in synthetic biology. A team of scientists from the Scripps Research Institute in La Jolla, California (USA) has presented one of the most advanced partially synthetic organisms to date. Specifically, experts have expanded the basic components of DNA to create a stable semi-synthetic organism, incorporating two artificial nucleotides (basic constituent of DNA) to a bacterium and that it has been able to read them to make proteins that are also artificial , as if from natural molecules it will be. This scientific milestone has been published in the journal Nature.
We already know that the DNA of living beings consists of adjustments of four basic nucleotides; However, this new way of life uses six, which makes the organism a very interesting being. It is made from the same regular nucleobases as all of us: adenine (A), cytosine (C), guanine (G), and thymine (T), but it also has two unnatural nucleotides, giving it two additional letters, X and Y, to form their DNA base pairs.
Already in 2014, this same team of researchers managed to incorporate this type of synthetic DNA base pairs to a modified form of the E. coli bacteria, creating the first living organism with additional letters in its DNA alphabet, which could hypothetically allow new ones. types of biological processes. The fault is that it was not stable. The semisynthetic organism could not maintain its unnatural nucleotides indefinitely during cell division.
And as lead researcher Floyd Romesberg says, “Your genome has to be stable for the scale of your life. If the semi-synthetic organism is really going to be an organism, it has to be able to stably hold that information.”
As a solution, the team devised a way for the semisynthetic organism to successfully latch onto its synthetic X and Y base pair, thanks to a new nucleotide transporter that allows for better DNA replication, an optimized Y molecule and a system of refined engineering; all this using CRISPR-Cas9 technology ( used to edit or correct the genome of any cell).
The base organism: a strain of the Escherichia coli species
The result was the first stable organism formed using the expanded 6-letter genetic code. Now, in the new study, the team announces further improvements to this kind of molecular stability, with a semisynthetic bacterium that can transcribe and translate its synthetic X and Y nucleotides just as efficiently as natural ones.
Thanks to a new transcription process, the microbe can synthesize proteins that contain non-basic amino acids (amino acids are the building block of proteins), and the process could shed light on new ways to replicate molecules with less dependence on the bonds of hydrogen. And it is that, instead of an alphabet of 20 letters (the amino acids), now there could be many more letters.
“This semi-synthetic organism is likely just the first of a new semi-synthetic life form that can access a wide range of forms and functions that are not available to natural organisms ,” the authors explain.
Reference: A semi-synthetic organism that stores and retrieves increased genetic information. Yorke Zhang, Jerod L. Ptacin, Emil C. Fischer, Hans R. Aerni, Carolina E. Caffaro, Kristine San Jose, Aaron W. Feldman, Court R. Turner & Floyd E. Romesberg. Nature 2017. doi: 10.1038 / nature24659
