Microcosm_ E. Coli and the New Science of Life - Carl Zimmer [96]
As Genentech’s fortunes waxed, the controversy over E. coli waned. Congress never passed a genetic engineering bill, thanks in part to fierce lobbying by scientists. The National Institutes of Health relaxed its guidelines. Scientists working on E. coli no longer had to dress up in space suits. Corporations snatched up E. coli experts in increasing numbers. All fourteen signatories to Paul Berg’s original moratorium letter ended up associated with one venture or another. Walter Gilbert helped launch a company called Biogen, which began engineering E. coli to spew out proteins that showed promise of fighting cancer. When Biogen opened its headquarters in Cambridge, Gilbert’s old nemesis, former mayor Alfred Vellucci, was there to cut the ribbon.
Genentech led the way for the new biotechnology. Humulin, its microbe-produced insulin, went on the market in 1983, and now 4 million people worldwide take the drug. Other companies make their own brands of E. coli–produced insulin, which are used by millions of other diabetics. Biotechnology firms have developed many other drugs from E. coli, ranging from human growth hormone to blood thinners. Today E. coli churns out vitamins and amino acids. Traditionally, cheese is made by spiking milk with rennet, an enzyme produced in cows’ stomachs. Now much of the cheese in stores is made with rennet produced by E. coli. Scientists are adding new genes to E. coli to see what sorts of new things they can produce, from biodegradable plastics to gasoline.
These advances have not come easily. Scientists cannot simply treat E. coli as a machine. The microbe is a living thing, and it responds to manipulation in unexpected ways. Packing the bacteria in a giant tank can cause them to suffocate in their own waste. Engineering them to produce huge amounts of insulin or some other foreign protein puts them under tremendous stress. If the proteins clump together, E. coli produces heat-shock proteins to try to untangle them. All the energy E. coli uses up coping with the stress is energy it cannot use to feed and grow. Scientists, like cooks perfecting recipes, have struggled to find solutions to these quandaries.
Thirty years have now passed since E. coli became the monster and the mule of genetic engineering. It remains one of biotechnology’s favorite microbes. Scientists continue to experiment on it to find new ways to manipulate genes and proteins. Its restriction enzymes are the blade of choice for slicing DNA, and its plasmids are the favored breeders of new copies of genes. But scientists can now insert these genes in many other species as well. In the 1980s, they began using the lessons they learned from E. coli to shuttle genes into other bacteria and into fungi. Scientists have also learned how to introduce genes into animal and plant cells. Paul Berg’s original dream has become real: it is now possible to load a gene on a virus such as SV40 and infect an isolated mammal cell. (Cells from the ovaries of Chinese hamsters are a popular choice.) An engineered cell can then multiply into a laboratory colony, which can then churn out a valuable protein.
It’s now also possible to inject genes into living plants. Genetically modified crops now grow across vast stretches of farmland in many countries. Some crops produce a toxin normally made by bacteria that kills insects. Others have been engineered to withstand a weed killer. Scientists have also succeeded in creating plants that can produce human antibodies and vaccines.
Even animals now acquire foreign genes from engineered viruses. Some researchers hope they will be able to treat genetic disorders by supplying cells with working copies of essential genes. Others are inserting genes directly into embryonic cells to produce animals with foreign genes throughout their bodies. Some scientists are trying to ease the pollution produced by farms with this sort of genetic engineering. One