BER Research Highlights

Search Date: August 21, 2017

20 Records match the search term(s):


December 06, 2010

A New Mechanism for Microbial Community Metabolism

Outside of laboratories, microbial species rarely exist in isolation. Many important environmental processes are actually mediated by complex communities of microbes. In many cases, two or more species have evolved to perform a cooperative metabolic activity that would be energetically unfavorable for either organism acting independently. Research published in the December 3 issue of Science and led by DOE scientist Derek Lovley of the University of Massachusetts, Amherst, describes a new mechanism by which the bacterium Geobacter metallireducens consumes ethanol, an important intermediate compound in oxygen free soils and sediments, in cooperation with a second organism Geobacter sulfureducens. For this reaction to yield energy for either partner, electrons produced from ethanol oxidation must be rapidly consumed. Although it was previously assumed that the first organism uses a hydrogen production mechanism to pass electrons to its partner, the authors have discovered that electrons are instead directly fed to G. sulfureducens via conductive "nanowires" called pili on the cell surface, resulting in much more efficient collaborative growth. These results provide important new clues on the fundamentals used by microbes to mediate important environmental processes such as carbon cycling and contaminant transformation and suggest intriguing new approaches to direct generation of electricity in microbial fuel cell systems.

Reference: Summers, Z.M., H. E. Fogarty, C. Leang, A. E. Franks, N. S. Malvankar, and D. R. Lovley. 2010. "Direct Electron Exchange Within Aggregates of an Evolved Syntrophic Coculture of Anaerobic Bacteria," Science 330:1413-15.

Contact: Dan Drell, SC-23.2, (301) 903-4742
Topic Areas:

Division: SC-23.2 Biological Systems Science Division, BER


December 06, 2010

New Approach for Studying Microbes in their Native Environment

Advances in proteomics techniques are enabling scientists to understand the mechanisms of in situ microbial metabolism associated with DOE relevant environmental processes, including site remediation and carbon sequestration. A multidisciplinary team of DOE researchers working at a field research site in Rifle, Colorado, has developed proteomic techniques to track changes in expressed metabolic pathways for environmentally relevant and dominant metal- and sulfate-reducing bacteria during tests of in situ uranium bioremediation. The team is developing these new techniques to advance the study of microorganisms in their natural environment and to mechanistically link microbial metabolism with changes in geochemistry observed in natural sediments. These approaches are advancing a more predictive understanding of biogeochemical processes associated with in situ uranium bioremediation but are also applicable to a broad range of DOE environmental challenges.

Reference: Callister, S.J., M.J. Wilkins, C.D. Nicora, K.H. Williams, J.F. Banfield, N.C. Verberkmoes, R.L. Hettich, L. N'Guessan, P.J. Mouser, H. Elifantz, R.D. Smith, D.R. Lovley, M.S. Lipton, and P.E. Long. 2010. "Analysis of Biostimulated Microbial Communities From Two Field Experiments Reveals Temporal and Spatial Differences in Proteome Profiles," Environmental Science & Technology. ASAP Article. DOI: 10.12021/ES101029f, Published on the web Nov-8-2010.

Contact: Robert T. Anderson, SC 23.1, (301) 903-5549
Topic Areas:

Division: SC-23.1 Climate and Environmental Sciences Division, BER


November 22, 2010

Interactions of Bacteria with Uranium in the Environment

Uranium in the 6+ oxidation state is quite soluble and can thus move rapidly in uranium-contaminated subsurface environments. In contrast, uranium in the 4+ state is highly insoluble, and is therefore less likely to move the subsurface environment. New research has identified important aspects of how bacteria reduce uranium 6+ to uranium 4+, showing that the latter is produced in a variety of forms, not just in the expected, simple form of uraninite (UO2). The authors of the new study used a variety of techniques at the Stanford Synchrotron Radiation Lightsource (SSRL) to characterize the products of uranium reduction in various microbial cultures, including x-ray absorption spectroscopy (XAS). The XAS experiments showed that many of the uranium 4+ products lacked the spectral peak characteristic of uraninite. Instead, a variety of complex solids involving uranium and phosphate, and in some cases also calcium were identified, as well as solids in which uranium 4+ is bound to the surface of the bacterial biomass. These results will be helpful in modeling the mobility of uranium species at contaminated DOE sites. The research was led by Rizlan Bernier-Latmani of the École Polytechnique Fédérale de Lausanne in Switzerland, and involved scientists at SSRL. It is just published online in Environmental Science & Technology.

Reference: Bernier-Latmani, R., et al. 2010. "Non-uraninite Products of Microbial U(VI) Reduction," Environmental Science & Technology, online November 11, 2010. DOI: 10.1021/es101675a

Contact: Roland F. Hirsch, SC-23.2, (301) 903-9009
Topic Areas:

Division: SC-23.1 Climate and Environmental Sciences Division, BER


November 22, 2010

New Roles for Microbes in the Mercury/Methyl Mercury Cycle

Mercury is a global pollutant released into the atmosphere during coal burning and into freshwater systems froma agricultural runoff and industrial discharge. Once in freshwater systems, microorganisms, known as d-proteobacteria, create methylmercury (MeHg), a highly toxic form of mercury that accumulates in biological systems. High concentrations of MeHg are detected in biota in the East Fork Poplar Creek in Oak Ridge, Tennessee, even though mercury producing weapons production activities at the Y-12 National Security complex were discontinued many years ago. Oak Ridge National Laboratory scientists recently characterized the impacts of mercury and uranium contamination on the diversity and structure of bacterial populations from the East Fork Poplar Creek and other nearby streams. The team sampled 6 different streams at select times over a year and demonstrated that specific microbial groupings (Verrucomicrobia and e-proteobacteria groupings) were most closely correlated with high MeHg levels, even though no bacteria in these groupings are known to have any role in MeHg generation. This is the first study to indicate an influence of MeHg on an existing microbial community, and suggests that bacteria within the Verrucomicrobia and the e-proteobacteria groupings have an important, but yet to be determined role in the overall Hg/MeHg cycle.

Reference: Vishnivetskaya T. A., J.J. Mosher, A. V. Palumbo, Z. K. Yang, M. Podar, S. D. Brown, S.C. Brooks, B. Gu, G. R. Southworth, M. M. Drake, C. C. Brandt, and D. A. Elias. 2010. "Mercury and Other Heavy Metals Influence Bacterial Community Structure in Contaminated Tennessee Streams," Applied and Environmental Microbiology, published online ahead of print on 5 November 2010, doi:10.1128/AEM.01715-10.

Contact: Paul E. Bayer, SC-23.1, (301) 903-5324
Topic Areas:

Division: SC-23.1 Climate and Environmental Sciences Division, BER


October 12, 2010

New Models of Uranium Migration at the Hanford Site Shed Light on its Persistance

Three recent modeling studies shed light on the importance of the coupled physical, chemical, and geological factors that have caused a uranium plume at the Hanford 300 Area to persist over three decades. In contrast, legacy models of the site predicted that natural flushing of the aquifer would reduce the uranium concentration in the groundwater to drinking water standards within 10 years. These new simulations, performed by different teams, ranged in duration from a few days to 20 years and in spatial scale from laboratory columns to a massive 3-D field-scale simulation of the Hanford 300 Area. The smaller scale experiments elucidated the importance of various geochemical factors that control the adsorption and release of uranium from sediments. The field scale simulations executed on ORNL’s Jaguar supercomputer (Hammond and Lichtner, 2010), tested how pore scale processes couple with larger scale factors to control the evolution of the uranium plume over longer time periods. The results indicate that rapid fluctuations in the Columbia River stage combined with the slow release of bound uranium from contaminated sediment are the primary cause for the persistent uranium plume at the Hanford 300 Area. These DOE funded modeling studies are guiding the design of additional field and laboratory investigations to better understand the spatial and temporal dynamics of the plume and to inform future remediation efforts at the site.

References: Hammond, G. E., and P. C. Lichtner. 2010. "Field-scale model for the natural attenuation of uranium at the Hanford 300 Area using high-performance computing," Water Resour. Res., 46, W09527, doi: 10.1029/2009WR008819.

Ma, R., C. Zheng, H. Prommer, J. Greskowiak, C. Liu, J. Zachara, and M. Rockhold. 2010. "A field-scale reactive transport model for U(VI) migration influenced by coupled multirate mass transfer and surface complexation reactions," Water Resour. Res., 46, W05509, doi: 10.1029/2009WR008168.

Greskowiak, J., H. Prommer, C. Liu, V. E. A. Post, R. Ma, C. Zheng, and J. M. Zachara. 2010. "Comparison of parameter sensitivities between laboratory and field-scale model of uranium transport in a dual domain, distributed rate reactive system," Water Resour. Res., 46, W05509, doi: 10.1029/2009WR008781.

Contact: Robert T. Anderson, SC 23.1, (301) 903-5549, David Lesmes, SC 23.1, (301) 903-2977
Topic Areas:

Division: SC-23.1 Climate and Environmental Sciences Division, BER


September 07, 2010

A New Approach to Understand Complex Microbial Communities

Microorganisms control the rates of numerous processes in the environment including contaminant degradation and biogeochemical cycling of carbon and other nutrients; however, they rarely perform these functions alone or in isolation. Microorganisms exist in communities whose dynamic activities and responses to environmental influences remain poorly understood. Building on the increasing availability of microbial species whose genomes have been sequenced, researchers at Oak Ridge National Laboratory developed a model system of three microbial species to probe the details of microbial community interactions and physiology. Co-cultures containing a Clostridia, Desulfovibrio and Geobacter species were used to examine carbon and energy flow in an anaerobic microbial community. The availability of genomic information for each microbe enabled the use of powerful techniques for analysis of gene and protein expression to understand the dynamic shifts in metabolism resulting from environmental changes and/or association or competition within the microbial community. The model system is applicable to numerous environmental processes where fermentative production of simple organic acids (by Clostridia) drives microbial metabolism such as sulfate-reduction (by Desulfovibrio) or iron reduction (by Geobacter). This project will advance our predictive understanding of microbial community interactions in a manner not previously possible and will increase our understanding of environmental processes relevant to DOE such as carbon and nutrient cycling in soils and contaminant biotransformation in contaminated groundwater.

Reference: Miller, L. D., J. J. Mosher, A. Venkateswaran, Z. K. Yang, A. V. Palumbo, T. J. Phelps, M. Podar, C. W. Schadt, and M. Keller. 2010. Establishment and metabolic analysis of a model microbial community for understanding trophic and electron accepting interactions of subsurface anaerobic environments. BMC Microbiology. 10:149

Contact: Robert T. Anderson, SC 23.1, (301) 903-5549, Joseph Graber, SC-23.2, (301) 903-1239
Topic Areas:

Division: SC-23.1 Climate and Environmental Sciences Division, BER


September 07, 2010

Uranium Isotopes Tell a Fractionating Story

Uranium is a risk-driving contaminant at many DOE sites and its mobility in groundwater is influenced by both geochemical and biological processes. Methods are needed to identify which biogeochemical processes influence uranium mobility so that we can develop more robust contaminant transport models. Researchers at the University of Illinois, Pacific Northwest National Laboratory and Lawrence Berkeley National Laboratory have developed an isotopic method based on U-238/U-235 ratios that can be used to distinguish between microbe-mediated (preferentially U-238) versus chemical (either isotope) reduction of uranium in contaminated subsurface environments. In the laboratory, soluble uranium [U(VI)] can be reduced to an insoluble species [U(IV)] either enzymatically, by microorganisms, or chemically, by species such as Fe(II) or sulfide. To accurately model the transport of uranium in groundwater, methods are needed that discriminate between enzymatic and chemical reduction of uranium. At a field research site in Colorado, stimulation of subsurface microbial communities produces a decrease in the concentration of soluble uranium co-incident with an increase in uranium-reducing microorganisms and the production of chemical reductants such as Fe(II) and sulfide. Samples collected during these tests indicated a preferential shift in the U-238/U-235 ratios consistent with an enzymatic reduction process. The results indicate that isotopic methods can be used to distinguish between biotic and abiotic processes influencing uranium reduction under bioremediation conditions and/or natural attenuation conditions in the environment. The technique is important in the development of more robust models of contaminant transport in groundwater at uranium-contaminated sites.

Reference: C.J. Bopp IV, C.C. Lundstrom, T.M. Johnson, R.A. Sanford, P.E. Long, K.H. Williams. (2010) "Uranium 238U/235U Isotope Ratios as Indicators of Reduction: Results from an in situ Biostimulation Experiment at Rifle, Colorado, U.S.A.," Environ. Sci. Technol. 44(15):5927-5933.

Contact: Robert T. Anderson, SC 23.1, (301) 903-5549
Topic Areas:

Division: SC-23.1 Climate and Environmental Sciences Division, BER


June 28, 2010

DOE Mass Spectrometry on Cover of Chemical & Engineering News

Mass spectrometry is a critical technique for analysis of complex biological systems. The technique is essential for DOE’s research into biofuel production and plays an important role in studying such diverse areas as low dose radiation biology, environmental contamination, and microbial capture of carbon dioxide. The Pacific Northwest National Laboratory (PNNL) has carried out much pioneering research in mass spectrometry and its application in systems biology. The June 21, 2010 issue of Chemical & Engineering News includes new developments at PNNL in its cover story on high resolution mass spectrometry. The cover photo shows Yehia Ibrahim at a high performance time-of-flight mass spectrometer in PNNL’s Environmental Molecular Sciences Laboratory (EMSL). Comments by PNNL scientist Richard D. Smith on the impact of the new technologies, being developed in part with American Reinvestment and Recovery Act (ARRA) funding through EMSL, are included in the story. The article also mentions the collaboration between the EMSL and the National High Magnetic Field Laboratory at Florida State University under a separate effort to develop the newest generation of mass spectrometric instruments.

Reference: Celia Henry Arnaud, “High-Res Mass Spec: Mass spectrometry users have more choices for high resolving power, from conventional ion cyclotron resonance to newer time of flight”, Chemical & Engineering News, June 21, 2010, pages 10–15.

Contact: Roland F. Hirsch, SC-23.2, (301) 903-9009
Topic Areas:

Division: SC-23.1 Climate and Environmental Sciences Division, BER


June 07, 2010

Bacteria Produce Distinct Form of Reduced Uranium

Some gram-negative microorganisms are known to reduce soluble uranium to insoluble uraninite [UO2(s)] forming the basis for in situ bioremediation or natural attenuation techniques for uranium in contaminated groundwater. But do all bacteria produce the same forms of reduced uranium? New results indicate that some gram-positive bacteria such as Desulfitobacteria, common to subsurface environments, also reduce soluble uranium but produce a mononuclear uranium species that differs from the commonly observed uraninite mineral form produced by gram-negative bacteria. Researchers from the Georgia Institute of Technology and Argonne National Laboratory working at the Advanced Photon Source (APS) show that Desulfitobacteria produce a form of reduced uranium that is likely coordinated with light atom shells such as C/N/O or S/P rather than the commonly observed uraninite mineral structure [UO2(s)]. The chemical identity of uranium species in subsurface environments is crucial to modeling the biogeochemical processes controlling contaminant transport at DOE sites. These results suggest that these alternate forms of reduced uranium also need to be characterized to be able to accurately predict uranium mobility/stability in reduced environments.

Reference: KE Fletcher, MI Boyanov, SH Thomas, Q. Wu, KM Kemner, FE Loeffler, (2010) Environ. Sci. Technol., 44(12): 4705-4709

Contact: Robert T. Anderson, SC 23.1, (301) 903-5549
Topic Areas:

Division: SC-23.1 Climate and Environmental Sciences Division, BER


June 07, 2010

Elemental Composition of Glass Used to Capture Nuclear Waste Makes a Difference

To better understand the structure and durability of aluminoborosilicate glass used to capture nuclear waste, Pacific Northwest National Laboratory scientists conducted systematic experiments with aluminum, boron, sodium and silicon, the four major components of nuclear waste glass. The team synthesized glasses with different concentrations of these elements and then, using the solid-state nuclear magnetic resonance capabilities at DOE's Environmental Molecular Sciences Laboratory at PNNL, along with flow-through dissolution experiments, they investigated how structural changes in the glass affected their dissolution as a function of pH and temperature. Results indicate that the dissolution rate for glass is controlled by rupturing the aluminum to oxygen bond or the silicon to oxygen bond. Determining how glass breaks and dissolves is paramount for improving the prediction of nuclear waste release from glass and it advances fundamental understanding of how minerals weather and cycle these elements in subsurface environments.

Reference: Pierce EM, LR Reed, WJ Shaw, BP McGrail, JP Icenhower, CF Windisch, Jr, EA Cordova, and J Broady. 2010. "Experimental Determination of the Effect of the Ratio of B/Al on Glass Dissolution along the Nepheline (NaAlSiO4)-Malinkoite (NaBSiO4) Join." Geochimica et Cosmochimica Acta 74(9):2634-2654.

Contact: Paul E. Bayer, SC-23.1, (301) 903-5324
Topic Areas:

Division: SC-23.1 Climate and Environmental Sciences Division, BER


June 07, 2010

Microorganisms "Breathe" Humic Particulates

Organic matter in the soil, such as humic substances, plays a key role in determining the fate and transport of radioactive and heavy metal contaminants in the subsurface. Just-published research has demonstrated for the first time that particulate humic substances can serve as electron carriers for anaerobic metabolism by microorganisms. The humic substances act to shuttle electrons between the microorganisms and iron oxide minerals. Recent reports have suggested that microbial communities in sedimentary environments may be networked via nanowires or other bacterial appendages (or secretions) capable of accepting and donating electrons derived from microbial metabolism. Thus, these redox active humic particulates, in coordination with appropriate mineral phases, could be an integral component of these microbial networks, and have a significant role in determining the chemical form - and the resulting mobility - of contaminants of interest to DOE. The research is published in the June 2010 issue of Nature Geoscience. It was conducted by DOE-funded scientists at the University of Wisconsin, Madison, and at laboratories in Germany.

Reference: E.E. Roden, A. Kappler, I. Bauer, J. Jiang, A. Paul, R. Stoesser, H. Konishi, H. Xu, (2010), Nature Geoscience, 3:417-421.

Contact: Robert T. Anderson, SC 23.1, (301) 903-5549, Roland F. Hirsch, SC-23.2, (301) 903-9009
Topic Areas:

Division: SC-23.1 Climate and Environmental Sciences Division, BER,SC-23.2 Biological Systems Science Division


May 24, 2010

New Method to Study Microbial "First Responder" Proteins

Proteins found in the surface membranes of cells are essential for maintaining normal biological functions in cells, and often are the "first responders" to environmental stimuli. But membrane proteins can be low in abundance and insoluble, making them challenging to quantify and purify. To meet this challenge, scientists at Pacific Northwest National Laboratory developed a strategy to quantify and purify proteins on the surface membranes of cells. Using capabilities at the Environmental Molecular Sciences Laboratory (EMSL), a team of scientists enriched surface membrane proteins expressed by the bacterium Shewanella oneidensis MR-1, using a membrane-impermeable chemical probe. By linking this method with post-digestion stable isotope labeling, surface proteins could be quantified. Armed with this technique, scientists can better study the function of many bacterial membrane proteins.

Reference: Zhang H, RN Brown, W-J Qian, ME Monroe, SO Purvine, RJ Moore, MA Gritsenko, L Shi, MF Romine, JK Fredrickson, L Paaa-Tolic, RD Smith, and MS Lipton. 2010. "Quantitative Analysis of Cell Surface Membrane Proteins using Membrane-Impermeable Chemical Probe Coupled with 18O Labeling." Journal of Proteome Research 9:2160-2169.

Contact: Marvin Stodolsky, SC-23.2, (301) 903-4475, Paul E. Bayer, SC-23.1, (301) 903-5324, Robert T. Anderson, SC 23.1, (301) 903-5549
Topic Areas:

Division: SC-23.1 Climate and Environmental Sciences Division, BER,SC-23.2 Biological Systems Science Division


May 10, 2010

Unraveling the Microbial Mechanism for Mercury Resistance

Some microbes can metabolize inorganic and organic mercury to less toxic forms using the MerR protein. Using small-angle X-ray scattering (SAXS) complemented by molecular dynamics simulations, a scientific team from the Universities of Tennessee, Georgia and California at San Francisco and Oak Ridge National Laboratory determined that when a single mercury ion binds to the MerR protein a structural change is induced. This structural change turns on the DNA transcription machinery for several other proteins and enzymes involved in removing the toxic mercury from the cell. Understanding the mechanism by which the proteins in these microorganisms bind to and metabolize mercury could be useful for identifying biological strategies for removing or transforming mercury in groundwater or soils.

Reference: Guo, H-B., A. Johs, J.M. Parks, L. Olliff, S.M. Miller, A.O. Summers, L. Liang and J.C. Smith. 2010. "Structure and Conformational Dynamics of the Metalloregulator MerR upon Binding of Hg(II)." Journal of Molecular Biology 398: 555-568.

Contact: Paul E. Bayer, SC-23.1, (301) 903-5324
Topic Areas:

Division: SC-23.1 Climate and Environmental Sciences Division, BER


May 03, 2010

Stressful Living in Contaminated Groundwater

Microorganisms are the primary drivers of key subsurface geochemical processes but we only have limited understanding of the composition and function of the microbial communities involved. "Metagenomic" sequencing is providing insights into the metabolic capabilities of these microbial communities and microbial adaptations to environmental changes. A multi-institutional team from the University of Oklahoma, Oak Ridge and Lawrence Berkeley National Laboratories, and the DOE Joint Genome Institute has now sequenced microbial community DNA isolated from groundwater at a site with low pH and high levels of uranium, technetium, nitrate, and organic solvents. The analysis reveals a significant reduction in microbial diversity from background and an overabundance of genes that confer tolerance for nitrate, heavy metals, and organic solvents. In addition, the overabundance of genes for DNA recombination and repair suggests the presence of lateral gene transfer induced by exposure to extreme environmental conditions. These results expand our understanding of how microbial communities adapt to and influence the fate of environmental contaminants.

Reference: Hemme, C.L., Y. Deng, T.J. Gentry, M.W. Fields, L. Wu, S. Barua, K. Barry, S.G. Tringe, D.B. Watson, Z. He, T.C. Hazen, J.M. Tiedje, E.M. Rubin, and J. Zhou. 2010. "Metagenomic Insights into Evolution of a Heavy Metal-Contaminated Groundwater Microbial Community." ISME Journal 4: 660-672.

Contact: Joseph Graber, SC-23.2, (301) 903-1239, Paul E. Bayer, SC-23.1, (301) 903-5324
Topic Areas:

Division: SC-23 BER


May 03, 2010

Subsurface Biogeobatteries: Geophysics meets Microbiology

Tracking subsurface microbial activity can be an important component in developing bioremediation or natural attenuation strategies but often requires costly drilling. New research on the production of electrical current by electrochemically reduced sediments in subsurface contaminant plumes formed as a result of microbial activity coupled to the production of reduced iron and sulfur minerals may provide a cheaper tracking alternative. Although known for some time, a research team led by the Colorado School of Mines developed a theoretical basis for linking the production of current to microbial activity in contaminated environments. The work lays a theoretical basis for "self-potential" (SP) techniques to map areas of microbially-mediated electrical anomalies in subsurface environments. SP can be a practical surface-deployed method to track the extent of microbial activity in subsurface environments.

Reference: Revil A, Mendonca, CA, Atekwana, EA, Kulessa B, Hubbard, SS, Bohlen, KJ. "Understanding Biogeobatteries: Where geophysics meets microbiology," Journal of Geophysical Research-Biogeosciences, 115:G00G02, doi:10.1029/2009JG001065 (2010).

Contact: Robert T. Anderson, SC 23.1, (301) 903-5549
Topic Areas:

Division: SC-23.1 Climate and Environmental Sciences Division, BER


April 26, 2010

Hydrogel-Encapsulated Soil: A New Tool to Measure Contaminant-Soil Interactions in the Subsurface

Measuring the transformation of contaminants such as radionuclides and heavy metals in the subsurface over time remains an important but difficult challenge. A team of scientists from Oak Ridge National Laboratory (ORNL) has developed a novel and powerful approach for encapsulating soils and sediments in polyacrylamide hydrogels called PELCAPs. The PELCAPs can be placed in the subsurface for extended periods of time, readily retrieved, and non-destructively assayed to observe and measure many water-solid contaminant interactions under natural groundwater flow conditions. The team showed that when PELCAPs were placed in a subsurface environment with uranium contaminated groundwater, uranium was adsorbed by the soils in the PELCAPs. The PELCAPs could be resampled over several years, the transformation of uranium-contaminated soil could be readily determined, and the hydrogel remained inert and fully functional. Finally, many different soils (limestone, Portland cement paste, activated charcoal and other materials) could be encapsulated for extended periods of time in the hydrogel. PELCAPs represent an important new tool for measuring contaminant-soil interactions in the subsurface.

Reference: Spalding, B., S.C. Brooks and D.B. Watson. 2010. "Hydrogel-Encapsulated Soil: A Tool to measure Contaminant Attenuation In Situ." Environmental Science & Technology 44(8):3-47-3051.

Contact: Paul E. Bayer, SC-23.1, (301) 903-5324
Topic Areas:

Division: SC-23.1 Climate and Environmental Sciences Division, BER


March 08, 2010

New Insight Into How Iron Oxide Minerals Influence Transport of Uranium in Subsurface

Iron-oxide minerals play a critical role in determining the mobility of subsurface contaminants such as uranium at DOE cleanup sites. Understanding how the surface reactivity of these minerals changes over time is critical to understanding uranium transport. Researchers funded by DOE and NSF at SLAC National Accelerator Laboratory and Stanford University have developed a new structural model that accounts for gaps in the mineral structure of ferrihydrite as it transforms to the more stable mineral hematite and shows that these gaps are likely to be important sites for the binding of contaminants such as uranium. Synchrotron-based studies led to a detailed analysis of the changes occurring in the mineral structure of ferrihydrite as it is converted to hematite. The research also produced new information about the interaction of microbes with these minerals and how these interactions influence the chemical form of uranium.

Reference: F. Marc Michel, Vidal Barrón, José Torrent, María P. Morales, Carlos J. Serna, Jean-François Boily, Qingsong Liu, Andrea Ambrosini, A. Cristina Cismasu, and Gordon E. Brown, Jr. "Ordered ferrimagnetic form of ferrihydrite reveals links among structure, composition, and magnetism," Proceedings of the National Academy of Sciences, 107: 2787-2792 (2010).

Contact: Robert T. Anderson, SC 23.1, (301) 903-5549
Topic Areas:

Division: SC-23.1 Climate and Environmental Sciences Division, BER


February 01, 2010

New Gene Tools Help Predict Microbial Growth in the Subsurface

Environmental microbes modify their growth and activity in response to changing nutrients in largely unknown ways. This complicates the development and use of predictive models of microbial metabolism in the environment. New gene expression tools now enable researchers to determine whether microbes are actively taking up phosphate for growth or not. The new tools developed by researchers at the University of Massachusetts, Lawrence Berkeley National Laboratory, Pacific Northwest National Laboratories, the J. Craig Venter Institute and the University of California-Berkeley enables researchers to assess phosphate bioavailability from the microbe's "point of view" and to use the information to calibrate and revise models of microbial growth in the environment and to directly test nutrient formulations for their bioavailability potential. These tools were tested during in situ field tests of uranium bioremediation and add to a growing set of tools advancing a predictive understanding of microbial communities in the environment. These new results were reported online at The ISME Journal (10 December 2009:1-14).

Contact: Robert T. Anderson, SC 23.1, (301) 903-5549
Topic Areas:

Division: SC-23.1 Climate and Environmental Sciences Division, BER


January 19, 2010

Electrodes Tap into Microbial Activity During Uranium Bioremediation

Microbes in subsurface environments can be used to remediate uranium-contaminated sites but scientists have not been able to monitor the progress of bioremediation without physically taking samples. Now, researchers from Lawrence Berkeley National Laboratory, Ruhr University, Pacific Northwest National Laboratory, and the University of Massachusetts have adapted microbial fuel cell techniques to the detection of microbial activity in the environment. Electrodes placed into the subsurface during uranium bioremediation provide a signal that correlates with acetate availability (a microbial energy source) demonstrating a new method to monitor microbial activity in the environment. The results suggest that electrical signals could be used to monitor the progress of bioremediation processes and provide real-time data for use in predictive models of microbial metabolism during uranium bioremediation. These techniques are not specific to uranium bioremediation and in fact could be used to detect microbial activity in a host of different environmental settings thereby allowing researchers to directly examine rates of microbial processes in environment. The results are reported in the latest addition of Environmental Science and Technology (2010) 44:47-54.

Contact: Robert T. Anderson, SC 23.1, (301) 903-5549
Topic Areas:

Division: SC-23.1 Climate and Environmental Sciences Division, BER


January 19, 2010

New Technique for Studying Biogeochemical Transformation on Uranium

Understanding the fate and transport of uranium in subsurface environments is a major concern for planning remediation of contamination at the DOE cleanup sites. Yet it is very difficult to study the biogeochemical processes that impact uranium mobility in these environments. Research at the Argonne National Laboratory has now led to a realistic laboratory-based approach that uses sediments from field contaminated locations in microcosms prepared and maintained under conditions that closely match those in the field. Tests of the new technique were carried out using sediment samples from the Oak Ridge National Laboratory Integrated Field-Research Challenge site. The microcosms were maintained under anaerobic (no oxygen) conditions to ensure that microbial activity would match that in the sampled subsurface field site. Changes in chemical characteristics of the uranium in each microcosm were determined periodically over an eleven month period using x-ray absorption spectroscopy beamlines at the Advanced Photon Source. Analysis of the results of these experiments, along with biochemical and geochemical data, indicates that at least two distinct processes are taking place that gradually transform the highly mobile uranium (VI) to highly immobile uranium (IV). The research has just been published in Environmental Science & Technology.

Reference: S.D. Kelly, et al., "Uranium transformations in static microcosms", Environ. Sci. Technol. 2010 44(1), 236-242.

Contact: Roland F. Hirsch, SC-23.2, (301) 903-9009
Topic Areas:

Division: SC-23.2 Biological Systems Science Division, BER