We are proud to announce a new paper coming out in the International Journal of Systematic and Evolutionary Microbiology, “Geobacter daltonii sp. nov., an iron(III)- and uranium(VI)-reducing bacterium isolated from the shallow subsurface exposed to mixed heavy metal and hydrocarbon contamination,” by Om Prakash, Tom Gihring, Dava Dalton, Kuki Chin, Stefan Green, Denise Akob, Greg Wanger, and Joel Kostka. This paper describes a new species of Geobacter isolated from the contaminated subsurface of a nuclear legacy waste site in Oak Ridge, Tennessee, managed by the U.S. Dept. of Energy.

In this paper, we isolated an iron(III)- and uranium(VI)-reducing bacterium from highly contaminated sediments of the Oak Ridge Integrated Field-Scale Subsurface Research Challenge (OR-IFRC) sponsored by the U.S. DOE Environmental Remediation Sciences Program (ERSP) and led by the Oak Ridge National Laboratory, in Oak Ridge, Tennessee. The sediments here are exposed to nuclear legacy waste contamination including radionuclides and hydrocarbons. Our analysis of the 16S rRNA gene and the Geobacteraceae-specific citrate synthase (gltA) mRNA gene sequences from ORFRC sediments indicate that this G. daltonii is both abundant and active in subsurface sediments undergoing uranium(VI) bioremediation.

Cells of G. daltonii are Gram-negative, non-spore forming, curved-rods and form pink colonies in a semisolid cultivation medium, a characteristic feature of the genus Geobacter, and is an obligate anaerobe. Similar to other members of the Geobacter group, G. daltonii conserves energy for growth from the respiration of Fe(III)-oxyhydroxide coupled to the oxidation of acetate. It is also highly versatile metabolically and, unlike its closest relative G. uraniireducens, can utilize formate, butyrate, and butanol as electron donors and soluble ferric iron (as ferric citrate) and elemental sulfur as electron acceptors. Based on the phylogenetic analysis and phenotypic differences we observed, in this paper we determine that this new strain is in fact a whole new species in the Geobacter genus and we name it Geobacter daltonii. The strain was named to honor Joel Kostka’s former laboratory technician Dava Dalton, an author on this paper who performed the initial isolation of the strain and tragically passed away shortly thereafter.

This paper has been a long time coming and many authors put a lot of effort into this project. Congratulations to everyone on this new and exciting publication!

Tags: Geobacter, New Species, Uranium, Iron

We have just received news that our proposal to the Department of Energy's Joint Genome Institute (JGI), "Sequencing the genomes of six novel denitrifying bacterial isolates from the uranium and nitrate contaminated subsurface at the U.S. DOE Oak Ridge Integrated Field Research Center (OR-IFRC)," has been funded and sequencing will begin over the next 6 months. The PI on the project, Stefan Green, has already submitted extracted DNA to the JGI for sequencing!

Very exciting news!

Tags: FRC, Oak Ridge, Denitrifyers, JGI

As a graduate student in the Kostka Lab, Denise Akob had the opportunity to spend the summer of 2007 as a guest scientist in the lab of Dr. Kirsten Küsel at the Friedrich-Schiller University Jena, Germany. The visit was supported by the Microbe-Mineral Interactions Graduate Research School which promotes international exchange of graduate students and scholars. During her time in Kirsten’s lab she worked in conjunction with Janna Sitte and Eva-Maria Burkhardt and focused on the biogeochemistry of microbial communities in surficial soils contaminated with radionuclides and heavy metals.

The Ronneburg Mining District during active uranium mining and before physical remediation efforts.
Photo: http://www.centennialpark.de/page/en/geschichte/geschichte

The site was within the former Ronneburg Mining District, which was an area that was heavily mined for uranium from 1946-1990. Much of the Ronneburg Mining District has now been physically remediated but groundwater runoff from a former leaching heap has contaminated the water and soils of the aquifer with acid mine drainage (AMD). The Gessen Creek, downstream from the former leaching site, is heavily impacted by AMD and processes in the creek soils are affecting transport of heavy metal contaminants. The research performed during Denise’s trip was focused on identifying the active microorganisms in Gessen Creek soils and relating microbial activity to mobilization/immoblization of heavy metals. The work started in the summer of 2007 is still in progress and will be a part of both Jana and Eva's PhD dissertations. In addition to this work, research has continued on microbial communities in Gessen Creek soils through the work of 1 bachelor’s student, 2 diploma students and a new PhD student. Stay tuned for more updates!

Photo of a drainage pond at a former leaching heap in the former Ronneburg Mining District. Photo: D. M. Akob, May 2007

Sampling of porewater profiles in Gessen Creek soils. Photo: D. M. Akob, May 2007

Tags: Bioremediation, Uranium, Mines, Ronneburg