A group of scientists has harnessed bacteria to bring the green dream of pollution-free chemical production a step closer to reality. For the cost of feeding them powdered sugar, bacteria may soon be used to produce medicines and other complex molecules without the usual burden on the environment.
The majority of complex molecules, such as medicines, fragrances, and flavorings that consumers use daily were invented by plants, fungi, and marine invertebrates. Chemical engineers have figured out how to synthesize many of these molecules in bulk, but the intricate reactions require expensive materials and often produce poisonous byproducts. In recent years, scientists have tried to turn fast-growing bacteria into chemical factories by transplanting the key genes responsible for the exotic chemistry. It's not easy, because the genes usually clash with the bacteria's own metabolism.
Molecular biologist Jay Keasling and colleagues at the University of California, Berkeley, report in the 1 June issue of Nature Biotechnology that they have overcome this hurdle. To prevent the genetic control mechanisms of Escherichia coli from interfering with the synthesis, they reconstructed an entire, self-sufficient metabolic pathway for a complex molecule and inserted it kit-and-kaboodle into E. coli bacteria. This stand-alone molecular assembly line consists of 10 genes--from a plant, yeast, and another bacterium--coding for the enzymes that allow the bacteria to assemble a complex molecule from its building blocks. The final product is the precursor of artemisinin, one of the few medicines to which African malaria parasites are still completely sensitive. So far the yield is less than cost effective, but Keasling says he will soon have his bacteria producing industrial quantities of the drug at a price affordable in the developing world, where malaria runs rampant. What's more, by swapping a couple genes, these bacteria can potentially produce any of the so-called isoprenoids, a large and diverse class of natural compounds.
"This is a real leap forward," says David Cane, a biochemist at Brown University in Providence, Rhode Island. Cane points out that the method is limited to natural chemicals for which the genes are known, but adds that such a chemical palate is "enormous."