CHAMPAIGN, Ill. The ability to describe the rates at which microbial populations metabolize in the natural environment has been limited by the lack of a general theory of microbial kinetics. Now, researchers at the University of Illinois have found an approach that holds significant promise for extending the results of laboratory experiments to better understand microbial metabolism in nature.

"The growth of microbial populations can have profound affects on the chemistry of groundwater, from acid-mine drainage in the West to arsenic poisoning in wells in Bangladesh," said Craig Bethke, a UI professor of geology. "The bulk of the worlds microbial biomass operates by eating rocks taking inorganic chemicals and using them to produce energy. By constructing quantitative models of that reaction process, we might find more effective solutions and control measures."

While various kinetic-rate laws currently exist, their empirical nature means they must be selected to match a given set of experimental results. "There is no guarantee that a rate law chosen to describe behavior observed in a laboratory culture will apply in a given geochemical environment," Bethke said. "Also, the available rate laws do not account for the amount of energy that might be derived by a given metabolism, further limiting their usefulness in modeling natural environments."

Graduate student Qusheng Jin and Bethke have devised a new description of microbial kinetics based upon the internal mechanisms of microbial respiration in terms of chemiosmotic theory. "In our approach, a cells metabolism is represented by a multi-step, enzymatically catalyzed reaction that is directly coupled to energy production by the development of a proton-motive force and the consequent synthesis of adenosine triphosphate from adenosine diphosphate," Bethke said. "We derive a rate law that accounts for the reactions thermodynamics and the energy required to produce ATP, as well as the abundance of
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Contact: James E. Kloeppel
kloeppel@uiuc.edu
217-244-1073
University of Illinois at Urbana-Champaign
14-Nov-2000