Mud Microbes
AMHERST, Massachusetts, January 18, 2002 (ENS) - Certain microorganisms can transform organic matter found at the bottom of the ocean into electrical energy, researchers at the University of Massachusetts have learned.
The microbiologists who discovered the process say that the microbes could someday be used to produce power for unmanned submarines or underwater sensing devices. The findings also have implications for many industrial and military applications, says Derek Lovley, leader of the UMass team.
An understanding of how microbes generate and use electrical energy may also prompt the development of new technologies to decontaminate polluted water and sediment containing organic materials, including petroleum and other aromatic hydrocarbons, Lovley said.
In an article in this week's issue of the journal "Science," Lovley explains how the team used water and sediment from Boston Harbor, a collection of mason jars, ordinary electrical wiring, and graphite electrodes to determine the science behind the mechanics of a simple, sediment battery.
The researchers added a layer of mud to water in the jars, put one graphite electrode in the mud, another in the overlying water. The resulting electrical current was strong enough to activate a lightbulb, or a simple computer.
"Even using a primitive electrode made from graphite," Lovley said, "it is possible to produce enough current to power basic electronic marine instruments."
Through more refined experiments, Lovley's group found that a family of energy harvesting microorganisms, called Geobacters, were key to the production of the electrical current. Most life forms get their energy by oxidizing organic compounds with oxygen, but Geobacters can grow in environments lacking oxygen by using the iron present in soil.
The new research demonstrates that Geobacters can also substitute an unnatural substance, such as an electrode, for the iron, Lovley explained.
"In the mud, a community of microorganisms cooperates to break down larger, more complex organic compounds to acetate," Lovley said. "Geobacters then transfer the electrons from the acetate to the electrode generating the electrical energy."
Lovley's group also has found that some Geobacters can convert toxic organic compounds, such as toluene, to electricity. Lovley says this suggests that some Geobacters could be used to harvest energy from waste matter, or to clean up organic contaminants such as petroleum.
"Once we know more about the genome of Geobacters, we will be able to manipulate these organisms to make them receptive to a variety of organic or inorganic contaminants," added Lovley. "Theoretically, when they begin to degrade the contaminant, they will throw electrons on an electrode, and that could set off a light, a sound or some other form of signal."
Such technology could lead to military equipment that could alert soldiers to the presence of toxins or biological warfare agents in the immediate environment, he added.
"An understanding of how this phenomenon operates has a number of extremely timely applications, especially in developing technologies to recognize toxins and organic contaminants," Lovley concluded.