Could genetically modified bacteria escape from a laboratory or fermentation tank and cause disease or ecological destruction? This is not known to have occurred. But two groups of scientists reported on Wednesday that they had developed a complex technique to prevent it from happening. The scientists have given a common type of bacterium a unique genetic code that makes it dependent for survival on unnatural amino acids that must be fed to it. If such organisms escaped into the wild, where those amino acids are not available, they would die. George Church, Robert Winthrop Professor of Genetics, leads one of the research teams.
