Scientists have engineered a strain of bacteria with a genetic code unlike anything found in nature, marking a groundbreaking advance in synthetic biology.
The microbe, called Syn57, is a lab-made version of Escherichia coli, a bacterium that normally causes infections in the gut, urinary tract and other parts of the body.
Unlike all known life, which relies on 64 codons, or three-letter DNA sequences that tell cells how to build proteins, Syn57 uses just 57 codons.
Think of DNA as a cookbook where each codon is a three-letter word telling the cell which amino acids, or ingredients, to use.
Life normally has some duplicate instructions, but Syn57 strips out the extras while still functioning perfectly.
These freed-up codons open the door to entirely new possibilities, allowing scientists to create proteins and synthetic compounds that nature has never produced.
Syn57’s unusual genetic code also makes it resistant to viruses, which rely on the standard DNA language to hijack cells. And because its code is so different, it is less likely to mix with natural organisms, easing safety concerns.
This breakthrough could also pave the way for new medicines, advanced materials and synthetic lifeforms beyond anything seen in nature.
The microbe, named Syn57, is a lab-engineered version of Escherichia coli, a bacterium that can naturally cause infections in the gut, urinary tract and other areas of the body
To tackle this huge project, scientists divided the genome into 38 pieces, each about 100,000 DNA letters long.
They built each piece in yeast and then inserted it into E coli using a method called uREXER, which combines CRISPR-Cas9 and other tools to swap in synthetic DNA in one step.
Some genome regions slowed growth or resisted changes, but the team solved these issues by adjusting gene sequences, untangling overlapping genes, and carefully choosing which codons to swap.
Step by step, the fragments were stitched together into the final, fully synthetic bacterium.
The result, Syn57, is the most heavily redesigned organism ever made, demonstrating that life can survive with a much smaller, simpler genetic code.
Wesley Robertson, a synthetic biologist at the Medical Research Council Laboratory in the UK, told the New York Times: ‘We definitely went through these periods where we were like, ‘Well, will this be a dead end, or can we see this through?’
Syn57 is alive, but barely. While normal E. coli can double in an hour, Syn57 takes four, making it ‘extremely feeble,’ Yonatan Chemla, a synthetic biologist at MIT who was not involved in the study.
The bacteria grew on a jelly-like surface and in a nutritious liquid, but at four times slower than their natural counterparts.
Dr Robertson and his team are now experimenting to see if they can make it grow faster.
If successful, scientists could eventually program it to do tasks that ordinary bacteria cannot.
In addition to the 20 standard amino acids that all life uses to make proteins, chemists can create hundreds of others.
Syn57’s seven missing codons could potentially be reassigned to these unnatural amino acids, allowing the bacterium to produce new drugs or other useful molecules.
Syn57 could also make engineered microbes safer for the environment.
Microbes swap genes easily, which can be risky if engineered DNA spreads.
But a gene from Syn57 would be gibberish to natural bacteria because of its unique genetic code, preventing it from being used outside the lab.
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