HR: 13:40h
AN: B13E-01    [Abstracts]
TI: Microscopic and Spectroscopic Characterization of Calcified Microorganisms at the Nanometer-Scale in Experimental and Field Samples.
AU: * Benzerara, K
EM: benzerar@stanford.edu
AF: Stanford University, Surface & Aqueous Geochemistry Group, Department of Geological and Environmental Sciences, Stanford, CA 94305 United States
AU: * Benzerara, K
EM: benzerar@stanford.edu
AF: Universite Paris 7, Laboratoire de Min‚ralogie-Cristallographie, UMR 7590, 4 place Jussieu, Paris, 75252 France
AU: Yoon, T
EM: taeyoon@stanford.edu
AF: Stanford University, Surface & Aqueous Geochemistry Group, Department of Geological and Environmental Sciences, Stanford, CA 94305 United States
AU: Menguy, N
EM: Nicolas.Menguy@lmcp.jussieu.fr
AF: Universite Paris 7, Laboratoire de Min‚ralogie-Cristallographie, UMR 7590, 4 place Jussieu, Paris, 75252 France
AU: Tyliszczak, T
EM: Tolek@lbl.gov
AF: Lawrence Berkeley National Laboratory, Chemical Sciences Division, Berkeley, CA 94720 United States
AU: Brown, G E
EM: gordon@pangea.stanford.edu
AF: Stanford University, Surface & Aqueous Geochemistry Group, Department of Geological and Environmental Sciences, Stanford, CA 94305 United States
AU: Brown, G E
EM: gordon@pangea.stanford.edu
AF: Stanford Synchrotron Radiation Laboratory, SLAC, 2575 Sand Hill Road, MS 99, Menlo Park, CA 94025 United States
AB: Calcium phosphates and calcium carbonates are the most prevalent minerals involved in microbial fossilization. Structural characterization of both the organic and mineral components in such samples is, however, usually difficult at the appropriate spatial resolution, i.e., at the submicrometer scale. We have used a combination of Scanning Transmission X-ray microscopy (STXM), a synchrotron-based technique, and High-Resolution Transmission Electron Microscopy (HRTEM) to characterize both the Ca-containing biominerals and the functional groups present in the organic components associated with them (STXM). These data, in turn, provide a better understanding of the mechanisms, products, and biomolecules involved in microbial calcification. We have studied the experimental biomineralization of the model strain Caulobacter crescentus by calcium phosphates, and the calcification of natural biofilms by aragonite in an alkaline lake in Turkey. The precipitation of calcium phosphate and calcium carbonate by microorganisms likely involves different mechanisms. The resulting biominerals were found to have unique features with dimensions in the nanometer-range, preferential crystallographic orientations or unusual morphologies, which provide potential biosignatures. By using C K-edge NEXAFS spectroscopy at a submicrometer scale, we were also able to document the evolution of the organic molecules during the fossilization process and to characterize those involved as templates in the formation of calcium phosphate and carbonate minerals.
DE: 4840 Microbiology
DE: 3600 MINERALOGY AND PETROLOGY (replaces
DE: 4803 Bacteria
DE: 1615 Biogeochemical processes (4805)
DE: 0400 Biogeosciences
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting