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-
     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
     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