An integrated approach to characterization of microbial exudates and investigation of their role in the spatial distribution and transformations of uranium at the mineral-microbe interface Page: 1 of 5
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An integrated approach to characterization of microbial exudates and investigation of their
role in the spatial distribution and transformations of uranium at the mineral-microbe
Argonne National Laboratory: K. M. Kemner*, E. J. O'Loughlin and S. D. Kelly (Argonne
National Laboratory, Biosciences Division, 9700 South Cass Avenue, Argonne, Illinois, 60439,
Kemner anl.gov (630) 252-1163
University of Southern California: K. H. Nealson
Research Objective: The long-term aim of this project was to understand the role of
microbiota and their polymers (EPS) in controlling the distribution and fates of contaminants in
subsurface environments. Additionally, this project also focused on the identification and
characterization of extracellular proteins under a variety of growth conditions. Finally, this
project sought to develop and advance the use of a variety of synchrotron-based hard-x-ray
techniques to address a number of different ERSP elements.
The technical goals related to (1) imaging the spatial distributions of radionuclide and metal
contaminants in mineral-microbe systems, and (2) determining the chemical speciation of the
contaminants in these systems. The scientific goals related to the determination of the role of
microbial exudates in microbial reduction and partitioning of metals and radionuclides between
the soluble and solid phases. The specific objectives of the project were to accomplish the
1. Develop x-ray and coupled x-ray-electron imaging methods; advance x-ray spectroscopic
methods for determining the spatial distribution and chemical speciation of Fe and U in
mineral-microbe systems; determine the detection limits and spatial resolution of the
2. Identify the exuded microbial polymers (e.g., polysaccharides, DNA, RNA, and
3. Determine the types and numbers of aqueous proton binding sites in microbial polymers
and relate them to metal binding properties.
4. Determine the spatial distribution and chemical speciation of U exposed to a variety of
microbial polymers from S. oneidensis MR-1 (and mutants) under conditions that should
lead to oxidation or reduction of each metal.
5. Determine the role of microbial polymers as they either promote or hinder U reduction,
even after the metal may have been released from (hydr)oxides by microbial reduction.
Research Progress and Implications: This final report summarizes work during FY2005 and
Mission relevance. This project was designed to generate information about the relationships
among microbial metabolic processes, microbial cell microenvironments, and aqueous and solid-
phase geochemistry related to the sequestration, release, precipitation, solubility, organic
complexation, and chemical modification (oxidation-reduction) of metals and radionuclides.
Such information is of the utmost importance for a better understanding of biotransformation
processes and biogeochemical interactions and for the development of science-based solutions
for cleanup of contaminated DOE sites, an effort consistent with the primary focus of the ERSP.
Potentiometric acid-base titration: We began acid-base titrations of EPS from S. oneidensis
MR-1 and from P. fluorescens. The aim was to observe and analyze differences in the proton-
binding behavior of a background electrolyte, the growth medium for the bacteria, the filtrate
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Kemner, K.M.; O'Loughlin, E.J.; Kelly, S.D. & Nealson, K.H. An integrated approach to characterization of microbial exudates and investigation of their role in the spatial distribution and transformations of uranium at the mineral-microbe interface, report, June 1, 2006; Argonne, Illinois. (digital.library.unt.edu/ark:/67531/metadc879030/m1/1/: accessed September 23, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.