Most of us like the idea of superpowers. Though we may never have the strength of Superman, we could be made stronger, faster, and even better-looking, with total control over our genome, or genetic makeup. What about becoming disease-resistant, weight gain resistant, and even slowing down the aging process? This might be possible in decades to come, as geneticists are now getting ever closer to, not just removing and replacing genes, but rewriting entire genomes. It sounds like the realm of science fiction. Yet, consider that geneticists at Harvard recently recoded the genome of a synthetic E. coli bacteria. Prof. George Church and colleagues conducted the study.
Researchers replaced 62,214 base pairs of DNA. What they have done is recreate the DNA from scratch, though they haven’t actually brought the bacteria to life, yet. What was once thought impossible is no longer. This is the first synthetic genome ever assembled, and is being hailed as the most complex feat of genetic engineering, thus far.
With this technique, we could create any kind of life form we wanted, reprogram organisms, and even create synthetic proteins and compounds. MIT bioengineer Peter Carr, told the journal Science, "It's not easy, but we can engineer life at profound scales.” Note that he was not involved in this project. So how exactly are they rewriting a genome? DNA is made up of four nucleobases which arrange themselves as base pairs, A and T, C and G. These create one strand of the double helix, known as RNA.
Chemical structures of nucleobases
Each combination equates to a certain amino acid, which is what cells are essentially made up of. Cell’s read combinations of nucleobases to know which amino acids to produce. There are only 64 possible combinations. When put in a group of three—called codons, they create a certain kind of amino acid. There are 20 different kinds in total. C-C-G for instance creates the amino acid proline. C-C-C does as well. So there is some overlap. In this way, geneticists can erase redundant genes without affecting the development of the organism.
That’s what Harvard geneticists did here. They edited out the overlap. Scientists removed seven of 64 codon types throughout 3,548 genes. Instead of editing the genome one gene at a time, researchers used machines to synthesize whole segments of RNA from scratch, each portion containing several alterations. Then they inserted these segments into the E. coli’s DNA, one-by-one, making sure as to not make changes that would destroy the cell. So far, 63% of recoded genes have been tested. Very few have caused any problems for the cell. Researchers still have several years of experimentation and testing ahead. Still, geneticists are marveling at how malleable the genome actually is.
Bacteria through electron microscope
In the near term, scientists are excited about the prospect of creating bacteria that is invulnerable to viruses. Usually, a virus infects a living cell by adding its own DNA to the host’s genome. In this way, it replicates itself. Genetically recoded organisms (GROs) would have a genome so different, the virus wouldn’t be able to read it and so couldn’t inject its DNA, making it unable to replicate.
One possible use for GROs is manufacturing. By rewriting a bacterium’s genetic code, it would change what kind of protein it makes. Synthetic bacteria could become living factories, programmed to produce whatever amino acid wished for. These would then churn out the next generation of synthetic materials, perhaps even medicines. Such engineered bacteria could also become reliable test subjects for future scientific research.
Prof. Church’s experiments have been controversial in the past. In that, one issue is whether or not this technique is 100% safe. The concern is that recoded bacteria could produce a toxin. Since it would be resistant to viruses, it would have an edge over competitors in the environment. If it should say get loose, it could result in ecological damage or even cause the next great plague. To overcome this concern, Church and colleagues have built a few safety measures into the system.
A special nutrient must be fed to these bacteria or else they die off. Unless they find this selfsame nutrient in the environment, which Church says is unlikely, they would not be able to survive. Another fail-safe is a special barrier which has been erected to make it impossible for the bacteria to mate or reproduce, outside of the lab. But other experts wonder how “unbeatable” Church’s fail-safe’s actually are. Carr says that instead of discussing these measures as foolproof, we should be framing it in degrees of risk.
The next step is further testing of the artificial genes that have been made. Afterward, Church and colleagues will take this same genome and produce an entirely new organism with it. Since DNA is the essential blueprint for almost all life on earth, being able to rewrite it could give humans an almost god-like power over it. That capability is perhaps decades away. Even so, combined with gene editing and gene modification, and the idea of a race of super humans is not outside the realm of possibility.