HR: 10:35h
AN: B12A-02 INVITED     [Abstracts]
TI: Protein Distribution and d34S Variation Within Microbially Formed Metal-Sulfide Colloids Provide Clues to the Mechanism and Kinetics of Extracellular Biomineralization
AU: * Moreau, J W
EM: moreau@eps.berkeley.edu
AF: Department of Earth and Planetary Science, University of California at Berkeley, 307 McCone Hall, Berkeley, CA 94720-4767 United States
AU: Weber, P K
EM: weber21@llnl.gov
AF: Chemical Biology and Nuclear Science Division, Lawrence Livermore Laboratory, L-231, P.O. Box 808 7000 East Avenue, Livermore, CA 94550 United States
AU: Martin, M C
EM: MCMartin@lbl.gov
AF: Advanced Light Source Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Bldg. 6R2100, Berkeley, CA 94720-8226 United States
AU: Webb, R I
EM: r.webb@uq.edu.au
AF: Centre for Microscopy and Microanalysis, The University of Queensland, Brisbane, Queensland, 4072 Australia
AU: Webb, R I
EM: r.webb@uq.edu.au
AF: Department of Microbiology and Parasitology, The University of Queensland, Brisbane, Queensland, 4072 Australia
AU: Hutcheon, I D
EM: hutcheon1@llnl.gov
AF: Chemical Biology and Nuclear Science Division, Lawrence Livermore Laboratory, L-231, P.O. Box 808 7000 East Avenue, Livermore, CA 94550 United States
AU: Banfield, J F
EM: jill@eps.berkeley.edu
AF: Department of Earth and Planetary Science, University of California at Berkeley, 307 McCone Hall, Berkeley, CA 94720-4767 United States
AU: Banfield, J F
EM: jill@eps.berkeley.edu
AF: Department of Environmental Science, Policy and Management, University of California at Berkeley, 307 McCone Hall, Berkeley, CA 94720-4767 United States
AB: Micron-scale spheroidal aggregates of 1-5 nanometer-diameter sphalerite and wurtzite particles form as the result of the activity of sulfate-reducing bacteria (Labrenz et al. 2000, Moreau et al. 2004). Because these particles can also sequester contaminant metal(loid)s such as Pb²⁺, Cd²⁺, As³⁺ and Hg²⁺, the process provides a model for the study of phenomena that occur during in situ environmental bioremediation. Our analyses have focused on biofilms growing on decaying wood in neutralized acid-mine drainage in subsurface regions of the flooded Piquette Mine near Tennyson, WI. The system experiences nearly constant annual temperatures of 8°C. Spectroscopic and electron diffraction methods revealed that the biogenic sulfides are virtually homogenous in composition (nearly pure ZnS), but contain both (cubic) sphalerite and metastable (hexagonal) wurtzite that reflect size-dependent phase stabilities. In order to explore the kinetics of sulfate reduction and metal sequestration, and to identify forces driving particle aggregation (thus, limiting their mobility in the subsurface), we have isotopically and biochemically characterized ultramicrotomed ZnS aggregates in situ using secondary ion mass spectrometry (nanoSIMS) and synchrotron Fourier transform infra-red spectroscopy (SR-FTIR). Initial nanoSIMS results showed that the spheroidal ZnS aggregates contain fine-scale variations in δ34S and significant organic nitrogen concentrations. SR-FTIR data support the presence of amide I and II absorption features indicative of the presence of polypeptides localized within aggregates. Efforts to isolate and identify candidate proteins are currently under way. We propose that isotopic heterogeneities may reflect open-system variations in the composition of local source sulfate (including via biologically-mediated reoxidation of biogenic sulfide), and/or variation in bacterial sulfate reduction rate over the growth cycle(s) of sulfate-reducers. Furthermore, we suggest that the flocculation of ZnS nanoparticles is promoted by association with dissolved extracellular biofilm proteins. This connection between proteins and the mineral byproducts of bacterial sulfate reduction suggests a more direct role for biomolecules in extracellular metal-sulfide mineralization than has previously been recognized.
DE: 0419 Biomineralization
DE: 0420 Biomolecular and chemical tracers
DE: 0424 Biosignatures and proxies
DE: 0448 Geomicrobiology
DE: 0454 Isotopic composition and chemistry (1041, 4870)
SC: Biogeosciences [B]
MN: Fall Meeting 2005