Abstract's Details

Adsorption of Metal Cations on Shewanella oneidensis Surfaces: Impact on Biofilm Coatings on Mineral Surface Reactivity
Abstract ID	ENV-10
Presenter	Alexandre Gélabert
Presentation Type	Poster
Full Author List	A. Gélabert (1), Y. Wang (1), G. Ona-Nguema (1), J. Ha (1), C. Cordova-Ardy (2), J. Gescher (2), J. R. Bargar (3), J. Rogers (3), P. J. Eng (4), S. K. Ghose (4)
Affiliations	(1) Surface & Aqueous Geochemistry Group, Dept. of Geological & Environmental Sciences, Stanford University, Stanford, CA 94305-2115, USA (2) Dept. of Civil & Environmental Engineering, Stanford University, Stanford, CA 94305, USA (3) Stanford Synchrotron Radiation Laboratory, SLAC, MS 69, 2575 Sand Hill Rd., Menlo Park, CA 94025, USA (4) Consortium for Advanced Radiation Sources, University of Chicago, Chicago, IL 60637, USA (5) USM 201 and CNRS UMR 7160, Museum National d'Histoire Naturelle, Paris, France
Category	Environmental Science
Abstract	Fe- and Al-(oxyhydr)oxides are commonly found in soils and are among the most reactive mineral surfaces in water-rock systems. Microbial colonies may be present as coatings on the surfaces of these minerals and thus may create local microenvironments, which could change significantly trace metal ion sorption and cycling compared to biofilm-free mineral surfaces. In this study, electrokinetic techniques were used to determine the influence of Shewanella oneidensis MR-1 (wild type) cells on the overall mineral surface charge, which affects reactivity. In addition, we quantified this influence, by determining the in-situ partitioning of Pb(II) between S. oneidensis MR-1 biofilms and highly polished and oriented single crystal surfaces of a-alumina (1-102) and hematite (0001) as a function of pH and [Pb] using the long-period X-ray standing wave-fluorescent yield (XSW-FY) method. GI-XAFS measurements at different X-ray incidence angles were also performed to assess the speciation and local coordination environment of Pb(II) at the mineral surfaces and within the biofilm. Electrophoretic mobility measurements of S. oneidensis MR-1 cell surfaces indicate that the surfaces become negatively charged at pH ~3.5, suggesting a high Pb(II) adsorption capacity of the bacterial biofilm. XSW-FY measurements on S. oneidensis biofilm/a-Al₂O₃ (1-102) and a-Fe₂O₃ (0001) interfaces under aerobic conditions indicate that Pb(II) is located at the mineral surface for low Pb(II) concentrations (10e-6 M to 10e-5 M) and is increasingly partitioned into the biofilm at higher concentrations (> 10e-5 M). Results of Pb L₃-edge GI-XAFS analysis of Pb(II)/S. oneidensis biofilm/a-hematite samples indicate that carboxyl groups are responsible for Pb complexation in the biofilm after 3 hours exposure at pH 6. Three times of exposure (30 minutes, 3 hours and 1 day) have also been tested during the XSW-FY measurements and indicate an evolution in the Pb(II) partitioning as a function of time, suggesting the existence of a diffusion controlled process for the complexation of Pb(II) at the biofilm/a-Al₂O₃ (1-102) and a-Fe₂O₃ (0001) interface. Combining these observations with the previously defined thermodynamic complexation model for S. oneidensis cells provides precise information on the nature of biofilm-induced microenvironments at mineral/biofilm/water interfaces.
Footnotes	add the following authors to abstract book: Francois Farges(1,5) Alfred M. Spormann(2) and Gordon E. Brown, Jr.(1,3)
Funding Acknowledgement