Transcript Expanded Genetic Code in a Bacterium

Expanded Genetic Code in a
Bacterium
Creating a Miniature Factory
Expanding the Genetic Code
• At the Scripps Institute in California, scientists
have engineered a bacterium with an
expanded genetic code.
• In addition to A, T, G, and C, they have added
to synthetic nucleotides: d5SICS and dNaM
(known as Y and X for short).
E coli with Expanded Genome
The synthetic nucleotides have
been created in such a way that
they are not rejected by DNA
Polymerase when it is
proofreading during DNA
Replication.
The cells naturally took the new
nitrogen bases into their
genome
They made matching base pairs
that face each other on either
side of the DNA double helix.
Factory Microbes
• The goal is for the cells with the synthetic
nucleotides to begin to produce “unnatural
proteins.”
• Naturally, only 20 amino acids are produced,
cells with the two new nucleotides can
produce up to 152 types of amino acids.
The Factories and Natural Selection
• Because they are alive, the microbial factories
could harness the power of evolution to rapidly
select and automatically find the most useful
(fittest) metabolic pathways to making the
desired proteins.
– Cells could produce thousands of variations on a
successful antibiotic in a fraction of the time it would
take traditional chemists.
– The 1000s of variations would then be subjected to
selection pressure to find the most effective and
efficiently made variants.