HR: 08:15h
AN: B21A-02 INVITED     [PDF]
TI: Molecular Mechanisms of Iron Oxyhydroxide Biomineralization
AU: * Chan, C S
EM: chan@eps.berkeley.edu
AF: Dept. of Earth and Planetary Science, Univerisity of California, 307 McCone Hall, Berkeley, CA 94720 United States
AU: Fakra, S
EM: sfakra@lbl.gov
AF: Advanced Light Source, Lawrence Berkeley Lab, 1 Cyclotron Rd, MS 2-400, Berkeley, CA 94720 United States
AU: De Stasio, G
EM: pupa@mail.src.wisc.edu
AF: Dept. of Physics and Synchrotron Radiation Center, University of Wisconsin, 3731 Schneider Dr., Stoughton, WI 53589 United States
AU: Banfield, J F
EM: jill@eps.berkeley.edu
AF: Dept. of Earth and Planetary Science, Univerisity of California, 307 McCone Hall, Berkeley, CA 94720 United States
AB: Neutrophilic iron-oxidizing microbes such as {\it Gallionella} and PV-1 (Emerson and Moyer, 1997) extrude polymers that become encrusted with iron oxides. Little is known about the identity of these polymers, their biological function and the roles they play in mineralization. To this end, we are investigating iron oxidizers in natural terrestrial iron-rich microbial mat communities, culturing and characterizing them in the laboratory and performing abiotic synthesis experiments based on the natural mineralization processes. Our sampling site is in a flooded former lead-zinc mine in Tennyson, WI, which is host to thick reddish-orange microbial mats. Scanning and transmission electron microscopy studies show that the mat is composed of iron oxide-covered stalks and sheaths (like those formed by {\it Gallionella} and {\it Leptothrix spp.}), as well as tangled masses of mineralized filaments. There is evidence of polymer influence on mineral phase and morphology in the form of extremely thin (few-unit cell wide), microns-long akaganeite ($\beta$-FeOOH) crystals at the center of these mineralized filaments. We are using synchrotron-based X-ray spectromicroscopy (PEEM-photoelectron emisson microscopy and STXM-scanning transmission X-ray microscopy), which has the ability to give chemical information on heterogenous samples at high spatial resolutions. Both PEEM and STXM show that these filaments contain polysaccharides, which are likely templating the akaganeite formation. Initial iron oxide synthesis experiments using model microbial polysaccharides support this hypothesis. Further synthesis and characterization by X-ray absorption and infrared spectroscopy methods is being performed in order to elucidate the molecular mechanisms of mineral nucleation and growth.
DE: 1045 Low-temperature geochemistry
DE: 3600 MINERALOGY AND PETROLOGY (replaces
SC: Biogeosciences [B]
MN: 2003 Fall Meeting