E. coli genome has been remade with 101,000 changes to its DNA

The recoded bacterium uses only 57 of the 64 possible genetic codes, freeing up seven to be used for different purposes

By Michael Le Page

31 July 2025

E. coli can cause severe illness, but is also often used in drug development

VICTOR HABBICK VISIONS/SCIENCE PHOTO LIBRARY

We have gone further than ever before in creating life that is unlike anything that has evolved naturally. The genome of an Escherichia coli bacterium has been redesigned on a computer to use just 57 of the 64 genetic codes, which were synthesised from scratch and then put into a living bacterium.

“This was a gargantuan effort,” says Wesley Robertson at the Medical Research Council Laboratory of Molecular Biology in Cambridge, UK.

His team did this to prove it is possible, but the 57-codon E. coli, called Syn57, could have commercial uses. With further changes, Syn57 could be made completely resistant to viral infections, a major advantage for industrial brewing of proteins for medicines, food or cosmetics. That is because viruses rely on their host to make proteins, so if the code is changed, viral proteins will come out wrong.

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With other tweaks, Syn57 could be used to produce proteins containing up to 27 different amino acids, whereas natural proteins contain only 20. These synthetic proteins could potentially do things that are unachievable with normal proteins.

A protein is a chain of amino acids assembled in the specific sequence laid down in a gene. Each set of three DNA letters, or codon, tells the protein-making factories which amino acids to add next, or when to stop because a protein is complete.