A living organism that possesses a fully synthetic and significantly altered DNA code has bene developed for the first time in the world by scientists. While being similar to its natural cousins, this living organism is a microbe which is a strain of a bacteria that is normally found in soil and the human gut. The only difference being that this organism is able to survive on a smaller set of genetic instructions.
The fact that a restricted genetic code can sustain life is proved by the bug’s existence. It also now would allow scientists to make drugs and useful materials from organisms whose biological machinery is commandeered. It could also add a new features such as virus resistance.
Before creating cells with a synthetic version of the altered genome, the DNA of the bacterium Escherichia coli (E coli) was read and redesigned for a period of two years by researchers at the laboratory of molecular biology at Cambridge University.
The artificial genome holds 4m base pairs, the units of the genetic code spelled out by the letters G, A, T and C. Printed in full on A4 sheets, it runs to 970 pages, making the genome the largest by far that scientists have ever built.
“It was completely unclear whether it was possible to make a genome this large and whether it was possible to change it so much,” said Jason Chin, an expert in synthetic biology who led the project.
The instructions it needs to function is stored in the DNA coiled up inside a cell. For example, the cell reads the DNA that encodes the right protein when it needs more protein to grow. The DNA letters are read in trios called codons, such as TCG and TCA.
64 codons are used by almost all life forms – ranging from jellyfish to humans. However the same job is done by many of them. 20 natural amino acids are made by 61 codons in total.
Removing some of its superfluous codons was the first step in the redesigning of the E coli that was undertaken by the Cambridge team. The bug’s DNA was completely studied by the scientists with the help of a computer. The scientists replaced TCG, a codon that makes an amino acid called serine, with SCG whenever they came across the former. AGC does the same job as TCG. This method was used to replace two more codons.
Every occurrence of the three codons from the bug’s genome had been removed by the scientists after they had made more than 18,000 such edits. Researchers then added piece by piece the redesigned genetic code to E coli – to replace its natural genome, after they had been chemically synthesized. This created the first living organism with a completely synthetic and radically altered DNA code and the results wer4e reported by the team in Nature.
“It’s pretty amazing,” said Chin.
“They have taken the field of synthetic genomics to a new level, not only successfully building the largest ever synthetic genome to date, but also making the most coding changes to a genome so far,” said Tom Ellis, a synthetic biology researcher at Imperial College London.
(Adapted from TheGuardian.com)