10:58 08 April 2008
NewScientist.com news service
Ewen Callaway
A new "Darwin chip" could make evolution as easy as pressing play.
Researchers have created an automated device that evolves a biological molecule on a chip filled with hundreds of miniature chambers.
The molecule, which stitches together strands of RNA, became 90 times more efficient after just 70 hours of evolution.
"It's survival of the fittest," says Brian Paegel, a biochemist at the Scripps Research Institute, in La Jolla, California, who led the study with colleague Gerald Joyce.
The experiment could be used in the future to evolve molecules – or even cells – to sense environmental pollutants, Paegel says.
Dispelling doubts
And by demonstrating natural selection in real-time, the device could also help dispel doubts over evolution in the classroom and beyond, says Joyce. "There's a whole bunch of people who think evolution is only theory, including some former presidential candidates."
While Darwin used natural selection to explain differences between species, his principles also work at the level of molecules.
RNA is usually used to create proteins from genes. But some kinds of RNA can perform tasks similar to protein enzymes. Paegel's team used just such an RNA molecule, or ligase, in their work.
In the process, the ligase sews another strand of RNA to itself and is then duplicated by a pair of proteins.
Because of occasional errors in copying, the new ligase molecule might work differently from its predecessor – sometimes better, and sometimes worse. Paegel's team wanted to see if they could evolve a better ligase by natural selection.
Evolving ability
To do this, they took a form of ligase that is not very good at recognising RNA molecules, and dumped it in a pool of RNA. After letting it duplicate for a while, the researchers gradually reduced the number of RNA molecules in the pool, meaning that only the more efficient copies of the ligase could survive.
All the reactions occurred in a miniature chamber on the "evolution chip". After reaching a specified level of efficiency, a miniature pump automatically sucked up a small amount of the contents and plopped it into a new chamber. This started another round of selection.
After 70 hours and billions of duplications, Paegel's team stopped the reaction and analysed the last few batches. The ligase molecules they pulled out were able to find and stitch RNA molecules 90 times more efficiently than the ligase the team started with.
'Tasty potato'
Other researchers have created similar evolution machines, but few as fast and simple as the automated chip. "It's a big technical advance,” says Jack Szostak, a biochemist at Harvard University. Other labs are likely to follow, he says. "It doesn't look that difficult to do."
The device might be able to evolve better sensors to detect environmental pollutants such as lead, Paegal says. Just as his team reduced the number of RNA molecules in the reaction to select for a better ligase, cutting the level of lead would select an improved lead sensor.
Paegel also hopes to use the Darwin chip to make molecules with new chemical properties, not just improved editions of old molecules.
"We took a potato and made a really tasty potato," says Pagael. "But we would really like to discover broccoli – something completely different."
Journal reference: PLoS Biology (DOI: 10.1371/journal.pbio.0060085)
Cool!
Yummy!