Genetic engineers have, in the latest New Scientist, devised a device that (deviously) speeds up the process of evolution:
For instance, a yeast engineered to churn out the antimalarial drug artemisinin has been hailed as one of the great success stories of synthetic biology. However, it took 150 person-years and cost $25 million to add or tweak around a dozen genes – and commercial production has yet to begin.
But George Church, a geneticist at Harvard Medical School in Boston, thinks there is a far quicker way: let evolution do all the hard work for us. Instead of trying to design every aspect of the genetic circuitry involved in a particular trait down to the last DNA letter, his idea is to come up with a relatively rough design, create lots of variants on this design and select the ones that work best.
The basic idea is hardly original; various forms of directed evolution are already used to design things as diverse as proteins and boats. Church’s group, however, has developed a machine for “evolving” entire organisms – and it works at an unprecedented scale and speed.
What’s different about Church’s machine is that it can target the genes that affect a particular characteristic and alter them in specific ways. That greatly increases the odds of success. Effectively, rather than spending years introducing one set of specific changes, bioengineers can try out thousands of combinations at once. Peter Carr, a bioengineer at MIT Media Lab who is part of the group developing the technology, describes it as “highly directed evolution”.
The first “evolution machine” was built by Harris Wang, a graduate student in Church’s lab. To prove it worked, he started with a strain of the E. coli bacterium that produced small quantities of lycopene, the pigment that makes tomatoes red. The strain was also modified to produce some viral enzymes. Next, he synthesised 50,000 DNA strands with sequences that almost matched parts of the 24 genes involved in lycopene production, but with a range of variations that he hoped would affect the amount of lycopene produced. The DNA and the bacteria were then put into the evolution machine.
The machine let the E. coli multiply, mixed them with the DNA strands, and applied an electric shock to open up the bacterial cells and let the DNA get inside.
It took Wang just three days to do better than the biosynthesis industry has managed in years. And it was no one-off – he has since repeated the trick for the textile dye indigo.
They’re actually trying to use the process to alter DNA itself, creating organisms that are immune to viruses. Including human stem cells, which can then make treatment recipients immune to viruses as well.
Which would be kind of a big deal.