Scientists rewrite life’s code to create virus-resistant bacteria

Researchers at the MRC Laboratory of Molecular Biology in Cambridge have engineered a synthetic strain of Escherichia coli, named Syn57, that operates with only 57 codons instead of the standard 64 used by nearly all known life forms. This represents the most radically compressed genetic code created to date. By removing redundant codons—specifically seven codons including those for serine, alanine, and one stop signal—the team replaced over 101,000 codon instances across the bacterium’s 4-megabase genome. The genome was reconstructed from 38 synthetic DNA fragments assembled using a novel technique called uREXER, which combines CRISPR-Cas9 and viral enzymes for precise DNA swapping. Syn57 retains normal growth and function despite its streamlined genetic code, freeing up codons that can be reassigned to incorporate non-canonical amino acids and produce novel synthetic polymers and materials with programmable properties. Importantly, the recoded genome may confer resistance to many viruses that depend