Researchers have figured out how to get yeast to produce morphine, codeine and other similar drugs and have immediately urged regulators to control these drug-brewing yeasts before people start trying to make them at home. They genetically engineered simple brewer's yeast, Saccharomyces cerevisiae, and came up with a strain that can make very complicated plant compounds that include opioid drugs such as morphine, as well as some antibiotics and muscle relaxants. It's an important technical step, because now these drugs have to be synthesized directly from plants—an inefficient process. The yeast process isn't that efficient yet, either, but once it's...