These microorganisms are used for a biological treatment of wastewater and are a good example of the power of catalysis, says Bruce Rittmann, professor of civil engineering. The red portions are densely packed clusters of bacteria that oxidize ammonium, which is a pollutant, turning it into nitrite. The green parts are smaller bacterial clusters that oxidize the nitrite, changing it into less harmful nitrate.

What is Catalysis? Catalysis is the chemical reaction brought about by a catalyst. A catalyst is the chemical version of a "matchmaker" because it physically brings together two chemicals in such a way that their chance to react is maximized. However, catalysts can't make a match between chemicals if there's no "chemistry." Instead, they make it possible for reactions to happen faster, fast enough to be used in environmental cleanup or to produce a chemical product. Catalysts take many forms. Some are porous solids, such as the platinum, rhodium and palladium meshes that remove nitrogen oxide from automobile exhaust. Others are protein molecules, called enzymes, that are contained in microorganisms. Still others are naturally occurring solids, such as manganese or iron ixides. No matter what the catalyst's structure, though, it speeds up reactions without being changed itself. The strong suit of the Center for Catalysis and Surface Science and the Institute for Environmental Catalysis is the expertise and scientific intuition of its researchers. They include experimentalists, who use various techniques to study the atomic structure of catalysts, and theorists, who test and model experimental results. For example, using advanced electron microscopy techniques, Laurence Marks, professor of materials science and engineering, and Vinayak Dravid, associate professor of materials science and engineering, photograph the catalysts' electronic structure, down to the nanometer. Scouting a separate trail, Peter Stair, professor of chemistry; Eric Weltz, professor of chemistry; and Randall Snurr, assistant professor of chemical engineering, map what happens over time -- to the byproducts of the reaction as well as the original chemicals. Linda Broadbelt, assistant professor of chemical engineering; Donald Ellis, professor of chemistry and physics and astronomy; Snurr; and Robert Zhou, at UOP LLC in Des Plaines, Ill., simulate these atomic and subatomic changes on computers, gathering information about the clusters and how their electrons behave. -- M.M. RETURN TO FEATURE STORY