The next big step toward the creation of life in the lab, Joyce says, will be to engineer (or evolve) a set of synthetic molecules that can perform metabolism as well as replication. Geneticist Jack W. Szostak of Harvard Medical School has developed nonbiological proteins that bind ATP, an energy-carrying chemical crucial to metabolism. Szostak's lab is also attempting to fashion protocells that encase RNA within tiny spheres of fatty acids, called micelles, that can form, merge and replicate spontaneously.
Even if biochemists do manage to cobble RNA and other basic compounds into some form of synthetic life, the engineered system will probably be so complex at first that it will hardly prove that natural life began in some similar way, four billion years ago. Joyce's replicators consist of a mere 50 chemical letters, but the odds of such a sequence appearing by chance are roughly one in 1030, he notes. "If it were six or even 10 letters long, then I'd say we might be in the realm of plausibility, where one could imagine them assembling spontaneously" in the primordial soup.
From Test-Tube Life to Diagnostic Tools
Creating life in the laboratory would be a momentous occasion for humanity, even if it is more molecular than Frankensteinian. But there may be more mundane uses for such chemistry. A paper in press at Nature Biotechnology, Gerald F. Joyce says, describes how his lab at the Scripps Research Institute in La Jolla, Calif., has modified RNA replicators so that they must perform a biochemical function to reproduce. The winners of that evolutionary race will be good candidates for a medical diagnostic, he thinks. Scott K. Silverman of the University of Illinois says the idea has merit: "Suppose you need to do detection in a dirty environment with lots of different chemicals present say you want to find Salmonella inside peanut butter. That's hard to do without purification steps. It would be useful to be able to evolve the diagnostic system so that it still finds the signal despite all the noise." W.W.G.
This article was originally published with the title Evolution in a Bottle.