Office of Biological and Environmental Research Weekly Report

July 14, 2008

Major Review Published on “DOE Microbe.” A major review on the systems biology of a key DOE environmental microbe, Shewanella oneidensis MR-1, has just been published on line by Nature Reviews Microbiology. Several years of coordinated research by the “Shewanella Federation,” an SC-funded, integrated, multi-disciplinary, multi-investigator team led by Jim Fredrickson of PNNL, is summarized on the biology of this microbe, a master of metabolism that can catabolize numerous carbon sources in the presence or absence of oxygen using a range of electron acceptors, including many metals that are contaminants at DOE sites. Ubiquitous among microbial communities from marine to soil environments, the Shewanellae are also important in carbon cycling. The genomes of over 20 Shewanellae strains have been sequenced at DOE’s sequencing facility enabling systems-biology research approaches based on comparative genomics. These analyses are illuminating the ecophysiology (which genes correlate with which environments) of these bacteria and are suggesting ways to exploit their remarkable metabolic versatility towards DOE missions of waste cleanup, carbon sequestration, and, possibly, bioenergy generation.

Media Interest: No

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

Geochemical Research Sheds Light on Plutonium Mobility in the Environment. There is a concern that the mobility of plutonium (Pu) in the environment at some DOE legacy waste sites may be increased due to the formation of complexes with the metal-complexing compound ethylenediaminetetraacetic acid (EDTA), which was co-disposed with Pu. At issue is whether EDTA enhances the solubility and therefore the mobility of Pu(IV). Researchers at Pacific Northwest National Laboratory examined the mobility of Pu(IV)-EDTA complexes under common environmental conditions and found that they are not as mobile as previously assumed. The complexation of Pu(IV) with EDTA is affected by competitive complexation reactions with other common inorganic species such as Fe, Al, Ca and Mg. EDTA also readily adsorbs to geologic materials and is biodegraded by microorganisms commonly found in the environment. These other competitive reactions ultimately reduce the potential for EDTA to complex and mobilize Pu in the environment suggesting that Pu(IV)-EDTA complexes are not responsible for the observed mobility of Pu in the environment.

Reference: Journal of Solution Chemistry, 2008, vol. 37:957-986.

Media Interest: No

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

Using Models to Identify the Role of Climate and Atmospheric Composition on Changes in the Lower Stratosphere. Department of Energy (DOE)-funded scientists have shown that the Community Atmosphere Model Version 3 (CAM3) can reproduce a variety of large-scale changes observed in climate and chemical composition in the stratosphere when forced with the observed sea-surface temperatures and surface concentrations of long-lived trace gases and ozone-depleting substances. They also used the same model to differentiate the role of chemically active composition (ozone, methane, and chlorofluorocarbons) and CO₂ changes on observed trends in the stratosphere. The simulations indicate that changes in CO₂ do not change the total ozone trend; however, CO₂ changes do lead to important differences in ozone in the upper part of the stratosphere. In contrast, changes in surface methane concentration drive changes in the globally averaged total ozone column through changes in tropospheric and stratospheric ozone columns. The model is capable of reproducing trends in the age of tropical air that were found in other studies and suggests that the relation between the upward velocity and mean age of tropical air breaks down in the upper stratosphere, above 20 hPa, in association with isentropic mixing above that level. These simulations suggest that keeping methane and ozone-depleting substances at their 1970 levels would have a significant impact, indicating the potential importance of controlling methane emissions.

REFERENCE: Lamarque J.-F., D.E. Kinnison, P.G. Hess and F.M. Vitt, 2008: Simulated lower stratospheric trends between 1970 and 2005: Identifying the role of climate and composition changes. J. Geophys. Res. VOL. 113, D12301, doi:10.1029/2007JD009277, 2008

Media Interest:  No

Contact: Anjuli Bamzai, SC-23.1, (301) 903-0294

DOE Investigator’s Review Article Featured on Cover of Chemical Physics Letters.

DOE investigator Dr. Haw Yang’s (LBNL and UC-Berkeley) review article, “Progress in Single-Molecule Tracking Spectroscopy” was highlighted on the cover of the May 27, 2008 issue of Chemical Physics Letters. Yang is a leader in the field of 3D tracking spectroscopy for single molecules. Normally, measurements are made in biological systems on the average properties of many molecules of a specific type, not on single molecules. However, the average properties of a specific molecular species does not capture the range of reactivity of the individual molecules that may be critical to illuminating mechanisms that control important cellular processes. Dr. Yang is pioneering the development of experimental approaches that will track single molecule movement in cells, correlating the location of a molecule with its biological and chemical actions, and producing insights about how specific systems function in cells. He is currently developing spectrometric techniques to track individual fluorescent molecules as they move in three dimensions. This technology will be used to reveal the detailed behavior of the Cellulosome, the molecular complex that plays a fundamental role in the degradation of cellulose, as it interacts with cellulosic plant material.

Media Interest: No

Contact: Arthur Katz, SC-23.2, (301) 903-4932