Natural and Accelerated Bioremediation Research (NABIR) Findings Published in Science


In the May 18, 2001, issue of the journal Science, NABIR researcher Dr. Terry Beveridge of the University of Guelph, Canada, and collaborators at the Virginia Polytechnic Institute and State University published a paper entitled “Bacterial recognition of mineral surfaces: Nanoscale interactions between Shewanella and alpha-FeOOH.” Shewanella oneidensis is a bacterium that can “respire” iron (oxy)hydroxide minerals, as well as metals such as chromium and uranium, in the absence of oxygen. Little is known about how bacteria might use a solid mineral substrate for respiration because of the difficulty in observing molecular level processes at the microbe-mineral interface. The researchers used a novel approach to examine the binding of metal reductases in the outer membrane of the bacterium to the mineral surface. Atomic force microscopy measured the binding strength between the bacterium and the mineral surface in the presence and absence of oxygen. Nanomechanical measurements showed an affinity between Shewanella and the iron containing mineral, goethite. This affinity was not measurable in the presence of oxygen or with minerals that were not respired. Molecular modeling suggested that an iron reductase protein in the outer membrane of the bacterium reduced the iron present in goethite as part of the respiratory process. This study is the first to measure microbe-mineral interactions at a nanoscale, and opens the possibility of combining nanoscale measurements with molecular genetics and mineralogy to identify all components of electron transfer in metal and radionuclide reduction during bacterial respiration.