Scientists hit a significant milestone in creating artificial life with the construction of an entirely synthetic E. coli genome from scratch.

A major step forward in the field of synthetic biology, it marks the first time that a living organism has ever been created with a genetic code that is completely manufactured by humans, not nature.

In a paper published in the journal Nature, researchers from the Medical Research Council Laboratory of Molecular Biology in Britain revealed that they were able to make an E. coli in the laboratory made up completely of synthetic genes.

Genes, Codons That Make Up The Genome

An organism's genome is made up of genes, each one of which is comprised of four nucleotide bases: adenine (A), thymine (T), guanine (G), and cytosine (C).

In most living organisms, these nucleotide bases are strung together in 64 groups of three known as "codons". Each three-letter combination corresponds to one of the 20 amino acids, which in turn are strung together to form proteins. Sixty-one codons produce the 20 amino acids, while the last three are stop codons that signal the end of production.

Study lead author Jason Chin, a molecular biologist at the MRC laboratory, explained to New York Times that he and his team were curious about all the redundancies in the genetic code. The researchers asked if all 64 codons are necessary to create life.

Making A New, More Streamlined Version Of E. Coli

To answer the question, Chin and his team set out to develop a new version of E. coli that only uses 61 codons to make all the amino acids that the organism needs. The researchers basically streamlined the DNA sequence by making serine with four codons instead of six and using two stop codons instead of three. With this technique, they completely redesigned the E. coli's genetic code, calling it Syn61.

The next challenge is actually making the bacteria. Since the genome was too complex to transfer into an E. coli in one go, the researchers had to build the genome in small segments and replace the original genome piece by piece until no natural segments were left. Amazingly, the E. coli survived, albeit elongated cells and slower to reproduce.

"For those of us who work in synthetic genomics, it's the headline, most exciting thing; they synthesized, built, and showed that a 4-million-base-pair synthetic genome could work," Tom Ellis, who reviewed the paper and is the director of the Center for Synthetic Biology at Imperial College London, told Gizmodo. "It's more than anyone had done before."

In the future, Chin and his colleagues hope to streamline the E. coli genome even further, removing more redundancies and simplifying the genetic code. Not only are they curious to find out how simple the genome could be while still supporting life, but it would leave researchers space to experiment with the extra codons and create new amino acids, proteins, and cells.

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