A Novel Strategy in the War on Waste
by Charlotte Overby, Illumination, Spring 2002
Page 1 | Page 2 | Page 3

Etched against vistas broken only by chain-link fences and admonitions against entry, radioactive detritus from our nuclear past scars huge tracts of America's public lands.

Scientific attempts to contain and clean up this potentially lethal litter have been conducted almost without pause since the dawn of the nuclear age. Fifty years and billions of dollars later, the eerie silence of places such as the Hanford Nuclear Reservation in western Washington, one of the world's first plutonium production facilities and a key player in the development of the nuclear bomb, mock these efforts.

Today, thanks in part to the efforts of an MU chemist, there is new hope for progress.

During the past four years, Judy Wall, professor of biochemistry at MU, has studied a species of bacteria that, with the help of geneticists, might one day be coaxed into consuming loads of depleted uranium, one of the most pernicious nuclear pollutants.

The trick involves teasing out the complexities of the invisible microorganisms responsible for natural biodegradation, Walls explains. Everything biodegrades--plants, rocks, people--it's a process as old as life itself. One seldom ponders the microorganisms that do the work, but they are as ubiquitous as the air we breathe -- both aerobic or anaerobic, above or below ground, inside and outside of our bodies.

When humans manipulate the conditions under which things naturally biodegrade, the process is called bioremediation. It is not a new technology--people have been using microbial processes to compost plant material, treat sewage and ferment various beverages for centuries. But the word itself is new--it first appeared in peer-reviewed scientific literature in 1987--and so is a great deal of bioremediation technology. This new technology seeks to further harness the abilities of natural microorganisms, such as bacteria and fungi, to remove, break down or contain some of the most pernicious contaminants in our environment.

Wall is leading a research effort, in partnership with the U.S. Department of Energy to apply bioremediation technology to one of the most hazardous contaminants of all: uranium. She is researching a bacterium's potential to clean up places -- perhaps one day Hanford and the more than 120 other sites in the U.S. deemed contaminated by the DOE -- that have been contaminated by uranium during mining, nuclear weapons processing or nuclear power plant accidents. Wall excels in knowing how to construct and control testing conditions for materials that may best be described as irascible--a metal that is radioactive and a miniscule bacterium that can perish from exposure to oxygen. Understanding how these two interact may lead to new approaches to cleaning up the more than 120 sites in the U.S. deemed contaminated by the DOE. The federal agency is funding Wall's research through its Natural and Accelerated Bioremediation Research program.

The bacterium in question is Desulfovibrio desulfuricans--the scientific name for the muck most people recognize as making stagnant water smell like rotten eggs. The odor results from how D. desulfuricans creates its energy. Microorganisms, including the common bacteria D. desulfuricans, are the most abundant life form on Earth. They obtain nutrients and energy for growth through the transfer of electrons from an energy source to an electron acceptor. In other words, they survive by "eating" donor electrons from one molecule and pushing them to another, which "accepts" them. Both molecules are changed by the transfer process. Each time a donor gives up electrons, it is said to be oxidized. The acceptor is described as reduced. D. desulfuricans takes electrons it receives from hydrogen and pushes or transfers them to sulfates, reducing the sulfates, when in the presence of oxygen, to bad-smelling sulfides. Come home from a long vacation and you may catch a whiff of it the first time you turn on the shower.