What is the synthetic cell?
Two days ago scientists at J. Craig Venter announced the creation of the first self-replicating synthetic cell, a bacteria with DNA made in a lab. How did they do it, and what does it mean for us in the future?
First up, the scientists didn’t make life out of nothing, and they didn’t make a new species. They recreated a bacteria that already existed, and developed the techniques to do it.
The bacteria is Mycoplasma mycoides. It’s a parasite which lives in cows, and some subspecies cause cow lung disease. It has a circular chromosome made of just under 600,000 base pairs, making it a small genome.
The scientists had the genome sequence of M. mycoides and split it into bite-size portions and then synthesised. Synthesising DNA is nothing new, scientists have been able to write DNA code for quite a while, and can write whatever code they want to.
These little chunks were put into yeast, which can be forced to absorb little bits of DNA. Inside the yeast, the chunks can be sewn together. It’s called recombination. The resulting medium chunks were taken out and put into more yeast to be sewn together making large chunks. There were 11 large chunks were put into more yeast, and sewn together into one complete genome.
Along the way and at the end they checked the code was right by doing PCR tests, genetic fingerprinting made famous by CSI.
Result: A synthetic genome, written by a computer and put together in yeast sweatshops.
Now they had to get it into a bacterial cell. At first they tried to put the DNA into bacterial cells of a similar species, M. capricolum. They ran into trouble at first, because the DNA they had was unmethylated (lacking methyl groups) and the bacteria destroys DNA which is unmethylated. It’s a clever defense mechanism, and they got around it by methylating the DNA before putting it in.
Finally success. The synthetic genome was put into an M. capricolum bacteria where it replaced the normal genome. The bacteria were controlled by the new, synthetic chromosome and were able to replicate billions of times.
What does it mean for us in the future? The technology these guys have developed could be used to alter the DNA of bacteria and make them do new things. From medicine to clean water, the benefits could be huge. We already have this ability to some extent, but it opens up some new doors.
Some organisations have raised concerns about the work. Could a new bacteria be unleashed and take over the world? Probably not. It’s hard to predict how new genes will work in cells, and everything is linked together in a way we don’t understand now. Too much tinkering to the genome will probably not be tolerated by the cell. And if it did get outside, it would probably be extinct pretty quickly because it doesn’t have thousands of years of evolution to prepare it for the world.
If it did get out, we could track it back to the company in charge. These guys watermarked their genome by adding some quotes into the DNA/protein code. Now that’s just epically geeky!
Gibson, D., & et al (2010). Creation of a Bacterial Cell Controlled by a Chemically Synthesized Genome Science DOI: 10.1126/science.1190719
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