Messenger - Vol. 3, No. 3, Page 10 Spring 1994 On Research From 'slave' cells to glowing bacteria Ever since beer was invented thousands of years ago, human beings have been exploiting normal cell activity to make a variety of products-from ethanol to yogurt. Now, researchers like Prasad Dhurjati, professor of chemical engineering, use genetic engineering techniques to "enslave" microorganisms, forcing them to generate large amounts of desirable proteins. By inserting specific genes and genetic switches (known as promoters) into a host organism, Dhurjati says, cells can be "domesticated" to serve as protein factories. Once perfected, the technique could lead to new pharmaceuticals and biomedical products, such as proteins that prevent blood clotting. "Right now, we're answering basic questions about how genetically engineered cells grow and make products, and how the process can be precisely controlled," says Dhurjati. Dhurjati also uses genetic engineering techniques to make bacteria "glow" when they're exposed to environmental pollutants. The glowing bacteria detect any toxic substances, even at levels below a single part per million. "When we measure the light produced by these bacteria," Dhurjati says, "we get a light 'signature' that is proportional to the amount of pollutant in the sample." The idea, proposed by DuPont Co. scientist Robert Larossa, exploits the phenomenon of bio-luminescence-the genetic trait that prompts fireflies and other organisms to glow, perhaps as a protective mechanism or mating signal. In collaboration with DuPont scientists, a method was developed to genetically combine bio-luminescence with the natural stress response of microorganisms such as the e coli bacteria. A "genetic switch" was added to activate the light-producing genes, prompting the host organism to glow when subjected to stress. Any damage to the organism's DNA, for example, will make it glow. Contaminants that cause proteins to unfold also trigger bio- luminescence. Glowing bacteria could serve as biosensors in many settings, says Dhurjati, who has been recognized by the National Science Foundation for his ability and the potential of his biochemical-engineering research. For instance, the invention might be incorporated into a simple probe suitable for field measurements. At a wastewater treatment plant, any sudden surge of pollutants could be instantly detected. And, because they're sensitive to all toxic substances, the glowing bacteria would eliminate the need for many expensive tests to detect different pollutants, from metals to organics. -Ginger Pinholster