Reducing the E. coli genome to a bare, viable minimum

Amazing stuff! How much genetic code is really necessary?

"To find out, they set out to remove as much of it as they could. They analyzed the four million pairs of nucleotides in E. coli’s genome, then scaled down from 64 codons by changing tiny fragments of DNA and checking to see if the organism survived. In cases where the changes caused damage, the researchers made repairs that sometimes involved creating wholly new sections of code.

In the end, they were able to engineer E. coli that used only 57 codons, requiring more than 100,000 codon changes. Though this synthetic version lived, it took four hours longer to double its population than the natural bacteria. Still, the success suggests that the redundancies of our genes are, well, just redundant ..."

From the abstract:

"The near-universal genetic code uses 64 codons to encode the 20 canonical amino acids and protein synthesis. Here we designed and generated Escherichia coli with a 4 Mb synthetic genome in which we replaced known occurrences of six sense codons and a stop codon with synonymous codons. The resulting organism, Syn57, uses 55 codons to encode the 20 canonical amino acids."

ScienceAdviser

Syn57 represents a new chapter in the genetic code of life (original news release) Total synthesis of E. coli with just 57 codons is a radical rewrite of the genetic code, proving life’s capabilities with seven fewer codons

Escherichia coli with a 57-codon genetic code (no public access)

Escherichia coli with a 57-codon genetic code (preprint, open access)

Fig. 1 Combining codon compression schemes to yield a 57-codon genome design.

Codons for the amino acids serine and alanine plus one stop codon were eliminated, requiring over 101,000 recoding events.