Man-made microbe with fully synthesised DNA grown in WORLD FIRST

The man-made microbe, a type of bacteria usually found in the human gut, is similar to its natural cousins but survives on a smaller set of genetic instructions. And the pioneering experiment is set to pave the way for commandeering biological machinery to design drugs and bolster virus resistance. The two-year experiment saw the Cambridge University researchers read and redesigned the DNA of the E.coli bacterium, before creating cells with an artificial version of the altered genome.

The synthetic genome holds 4 million units of genetic code spelled out by the letters G, A, T and C.

It was completely unclear whether it was possible to make a genome this large and whether it was possible to change it so much

Dr Jason Chin

And if printed in full on A4 sheets, it runs to 970 pages, making the genome the largest ever built.

Dr Jason Chin, an expert in synthetic biology who led the project, said: “It was completely unclear whether it was possible to make a genome this large and whether it was possible to change it so much.”

The DNA coiled up inside a cell holds the instructions it needs to function.

When the cell needs more protein to grow, for example, it reads the DNA that encodes the right protein. The DNA letters are read in trios called codons, such as TCG and TCA.

Nearly all life, from jellyfish to humans, uses 64 codons, however many of them do the same job.

In total, 61 codons make 20 natural amino acids, which can be strung together like beads on a string to build any protein in nature.

Three more codons are in effect stop signs: they tell the cell when the protein is done, like the full stop.

The Cambridge team set out to redesign the E coli genome by removing any unnecessary codons. Working on a computer, the scientists went through the bug’s DNA.

Whenever they came across TCG, for example, they rewrote it as AGC, which does the same job – making a certain type of amino acid.

More than 18,000 edits later, the scientists had removed every occurrence of the three codons from the bug’s genome.

The redesigned genetic code was then chemically synthesised and, piece by piece, added to E coli where it replaced the organism’s natural genome.

The result is a microbe with a completely synthetic and radically altered DNA code.

Such designer lifeforms could revolutionise healthcare in the future.

Because their DNA is different, invading viruses will struggle to spread inside them, making them in effect virus-resistant.

E coli is already used by the biopharmaceutical industry to make insulin for diabetes and other medical compounds for cancer, multiple sclerosis, heart attacks and eye disease.

However entire production runs can be spoiled when bacterial cultures are contaminated with viruses or other microbes.

The freed-up genetic code could in the future be repurposed to make cells churn out designer enzymes, proteins and drugs.

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