Scientists in the UK have rewritten one of life’s oldest operating systems. They have built a bacterium that functions with a stripped-down genetic code, eliminating seven of the 64 instructions used by every known organism on Earth.
The team at the Medical Research Council’s Laboratory of Molecular Biology calls their creation Syn57. It is a synthetic strain of E. coli, a bacterium notorious for causing food poisoning. Yet Syn57’s genome is like no other. Instead of the 64 “codons” that all living things use, it runs on just 57.
The 57-Codon Organism
A codon is a three-letter ‘word’ written in DNA or RNA. Codons tell a cell which amino acid to add next as it builds proteins—the essential molecules that carry out nearly every job in a cell. Life evolved to use 64 codons to spell out just 20 amino acids and a handful of punctuation marks for starting and stopping protein chains. That redundancy raised a question that lingered for decades: Could organisms function with fewer codons?
Jason Chin, who led the Cambridge team, thought the answer might be ‘yes’. But proving it meant redesigning a genome from scratch. “This was a gargantuan effort,” said Wesley Robertson, one of the lead authors, as per New Scientist.
The researchers started by identifying codons that seemed redundant. They targeted four of the six codons for serine, two of the four for alanine, and one of the three stop signals. Then came the hard part: swapping out every instance of these codons across the bacterium’s four-million-letter genome. In total, more than 101,000 genetic changes were planned on a computer, then painstakingly built and tested in fragments before stitching the entire genome together.
At several points, the team hit dead ends. “We definitely went through these periods where we were like, ‘Well, will this be a dead end, or can we see this through?’” Robertson told New York Times. They pressed on, refining sequences and even evolving strains to recover growth when recoding caused problems.
But at last, they managed to assemble a living bacterium that uses only 57 codons. “Life still works,” Robertson added.
Why This Matters
The techniques involved in making Syn57 could become a powerful new tool for scientists. By freeing up codons, researchers can assign them new meanings. They could, for instance, reprogram Syn57 to incorporate non-natural amino acids, expanding proteins beyond biology’s standard 20. That could lead to new medicines, advanced materials, or entirely new forms of chemistry.
There is another advantage: viral resistance. Viruses infect cells by hijacking their genetic machinery. But Syn57’s genetic code is partly illegible to natural viruses. If a virus tries to take over, the instructions come out garbled. “We can then prevent the escape of information from our synthetic organism,” Robertson explained. That could make Syn57 and its descendants invaluable for industries that rely on bacterial workhorses to produce insulin, enzymes, or food ingredients—processes often threatened by viral outbreaks.
Still, Syn57 isn’t perfect. It grows more slowly than ordinary E. coli. The Cambridge team is now working to improve its fitness. “We anticipate that we’ll be able to improve the growth rate, so that it will be more useful,” Robertson said.
A New Chapter in Synthetic Biology
The journey to Syn57 builds on decades of effort. In 2010, scientists at the J. Craig Venter Institute made the first synthetic bacterial cell, but it used the full 64-codon code. In 2019, Chin’s group unveiled Syn61, which trimmed the code down by three codons. Syn57 pushes further, demonstrating that life can survive a much deeper rewrite.
For now, the team plans to explore Syn57’s potential rather than compress the code further. But the principle is clear: life’s genetic system is not fixed. It can be rewritten, repurposed, and expanded in ways evolution never tried.
“This work exemplifies how genome synthesis can move the genome sequences of organisms into new regions of sequence space that may not have been accessed by natural life,” the researchers wrote in their paper.
If biology is a language, Syn57 suggests we have only begun to experiment with its grammar. Evolution’s script is not set in stone but editable… and that opens the possibility of entirely new forms of life.
