Natalie Angier in The New York Times:
Dr. Arnold won fame and the Nobel Prize for developing a technique called directed evolution, a way of generating a host of novel enzymes and other biomolecules that can be put to any number of uses — detoxifying a chemical spill, or example, or disrupting the mating dance of an agricultural pest. Or removing laundry stains in eco-friendly cold water, or making drugs without relying on eco-hostile metal catalysts. Rather than seeking to design new proteins rationally, piece by carefully calculated piece — as many protein chemists have tried and mostly failed to do — the Arnold approach lets basic evolutionary algorithms do the work of protein composition and protein upgrades. The recipe is indeed an engineer’s dream: simple. You start with a protein that already has some features you’re interested in, such as stability in high heat or a knack for clipping apart fats. Using a standard lab trick such as polymerase chain reaction, you randomly mutate the gene that encodes the protein. Then you look for slight improvements in the resulting protein — a quickened pace of activity, say, or a vague inclination to carry out a task it wasn’t performing before, or a willingness to operate under conditions it deplored in the past.
…Through directed evolution, Dr. Arnold’s lab has generated microbes that do what organisms in nature have never been known to do. Some of them, for instance, stitch together carbon, the element that defines life, and silicon, the stuff of sand, glass and computer chips but heretofore not of life (unless you are a Horta, the rock-shaped beings who famously mind-melded with Mr. Spock on “Star Trek”). All it took were a few mutational tweaks to a bacterial protein called cytochrome c. “We showed for the first time that living organisms can use their own machinery to bring carbon and silicon together to form a bond,” said Jennifer Kan, a postdoctoral scholar in Dr. Arnold’s lab who performed the experiments. “We didn’t even have to nag the protein too hard to get it to do it.”