HR: 09:30h
AN: B11A-06    [PDF]
TI: Putative Mineral-Specific Proteins Synthesized by the Metal Reducing Bacterium {\it Shewanella oneidensis}
AU: * Lower, B H
EM: blower@vt.edu
AF: Virginia Tech, Department of Geological Sciences, Blacksburg, VA 24061 United States
AU: Hochella, M F
EM: hochella@vt.edu
AF: Virginia Tech, Department of Geological Sciences, Blacksburg, VA 24061 United States
AU: Lower, S K
EM: lower.9@osu.edu
AF: Ohio State University, Department of Geological Sciences, Columbus, OH 43210 United States
AB: For over three billion years the Earth has been home to millions of different species of prokaryotic organisms. The life and propagation of many of these microbial cells has relied on intimate contact with mineral surfaces (e.g., the use of metal oxides as terminal electron acceptors). An interface is formed at the junction of a bacterium and a mineral surface that is, by its very nature, nanoscale in size. The process of natural selection has shaped bacteria such that they are masters of the art of synthesizing fully functional structures and utilizing properties that exist only at the nanometer scale. We have begun to explore the bacterium-mineral interface to determine precisely how fundamental, nanoscale forces guide and are themselves modulated by a cell's expression of outer membrane proteins localized at a mineral surface. Recent work in our laboratory suggests that a species of dissimilatory metal reducing bacteria expresses proteins that have a high affinity for specific mineral phases. Using biological force microscopy (BFM), we have discovered that one such organism, {\it Shewanella oneidensis}, appears to recognize the surface of iron hydroxides - versus isostructural aluminum hydroxide counterparts - such that it produces and/or localizes putative mineral-specific proteins at the interface with goethite (FeOOH). These particular high molecular weight proteins are expressed only under anaerobic conditions, when the Fe(III) in the mineral phase is expected to serve as the microorganism's terminal electron acceptor. Protein expression patterns provided by two-dimensional gel electrophoresis confirm that specific, high molecular weight proteins are targeted to the outer membrane of {\it S. oneidensis} when Fe(III) is provided as a terminal electron acceptor. The results suggest that these proteins are synthesized by {\it S. oneidensis} under anaerobic conditions to function in iron oxide binding and/or Fe(III) reduction. If this is the case, than it is possible that the evolution of dissimilatory iron-reducing bacteria like {\it Shewanella}, could have been, at least in part, driven by the binding/reduction ability of certain proteins to specific mineral phases.
DE: 0400 Biogeosciences
SC: Biogeosciences [B]
MN: 2003 Fall Meeting