The work has been described as the first step towards a new biology because the techniques used should open the door to reinventing the meaning of several genetic words simultaneously, potentially creating new types of biomaterials and drugs.

The engineered bacteria, dubbed genetically recoded organisms (GROs), have the added advantage of being resistant to many existing viruses. They are also less likely to escape the lab and survive than conventional genetically modified organisms, which should make them more palatable for commercial use.

The four letters of the genetic code are usually read by a cell's protein-production machinery, the ribosome, in sets of three letters called codons. Each codon "word" provides instructions about which amino acid to add next to a growing peptide chain.

Although there are 64 ways of combining four letters, only 61 codons are used to encode the 20 amino acids found in nature. This means that some of the codons encode the same amino acid – a phenomenon called redundancy.