Don’t get too excited, no one’s creating synthetic humans just yet, it’s still only a microbe. The synthetic organism is actually a strain of bacteria that is normally found in soil and the human gut. It’s quite similar to its natural cousins however this one survives on a smaller set of genetic instructions.
The microbe in question is Escherichia coli (E. coli), a bacteria found in a number of places. After a two-year effort, researchers at the laboratory of molecular biology, at Cambridge University, read and redesigned the DNA of the bacterium before creating cells with a synthetic version of the altered genome.
The new and arguably improved artificial genome holds 4m base pairs, the units of the genetic code spelled out by the letters G, A, T and C. Printed in full on A4 sheets, it runs to 970 pages, making the genome the largest by far that scientists have ever built, which is absolutely remarkable.
According to Jason Chin, an expert in synthetic biology who leads the project, no one knew whether it was even possible to make a genome this large and whether it was possible to change it so much.
The DNA which is coiled up inside a cell holds all the instructions that the cell needs to function properly. For example, when the cell needs more protein to grow, it reads the DNA that encodes the right protein. The DNA letters are read in trios called codons, such as TCG and TCA. Pretty much everything living thing, ranging 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 and are in charge of telling the cell when the protein is done. Similar to how a full stop/period signals the end of a sentence, these three codons tell the cells when the proteins are finished.
Redesign of E. Coli
The initial redesign of the E. coli genome by the Cambridge team was to involve the removing of some of its superfluous codons. Working on a computer, the scientists trawled through a bug’s DNA and whenever they came across TCG, which is a codon that makes an amino acid called serine, they rewrote it as AGC, which effectively does the same job. It seems pretty simple, but extremely effective and has dramatic effects on the bacteria. They did the exact same to two other codons too.
After more than 18,000 edits, it was almost completed. The scientists had managed to remove every occurrence of the three codons from the bug’s genome. The redesigned genetic code was then chemically synthesized and, piece by piece added to E. coli where it replaced the organism’s natural genome. The resulting microbe has a completely synthetic and radically altered DNA code. Known as Syn61, the bug is a little longer than normal, and grows more slowly, but can still survive nonetheless.
Chin says that this is some pretty amazing work. When the bug was created, shortly before Christmas, the research team had a photo taken in the lab with a plate of the microbes as the central figure in a festive recreation of the nativity, with a scientific twist of course. Chin says that such designer lifeforms could come in handy one day. Due to their DNA being so different, invading viruses will struggle to spread inside them, making them in effect virus-resistant. That could bring many benefits.