MOLECULAR MECHANISM OF URANIUM REDUCTION BY CLOSTRIDIA AND ITS MANIPULATION. Page: 3 of 7

Molecular Mechanism of Uranium Reduction by Clostridia and its
Manipulation
A. J. Francis (PI), W. Gao, D. Chidambaram, and C.J. Dodge
Environmental Sciences Department, Brookhaven National Laboratory, Upton, NY 11973
RESEARCH OBJECTIVES
This research addresses the need for detailed studies of the enzymatic mechanisms for
reduction of radionuclides and/or metals by fermentative microorganisms. The overall objective
of this research is to elucidate systematically the molecular mechanisms involved in the
reduction of uranium by Clostridia. We propose to (i) determine the role of hydrogenases in
uranium reduction, (ii) purify the enzymes involved in uranium reduction, (iii) determine the
mechanisms of reduction, e.g., one or two electron transfer reactions, and (iv) elucidate the
genetic control of the enzymes and cellular factors involved in uranium reduction.
This is a collaborative study between BNL and Stanford University involving expertise in
biomolecular science, biochemistry, microbiology, and electrochemistry.
RESEARCH PROGRESS AND IMPLICATIONS
This report summarizes the work after 1 year of a 3 year project. We have accomplished
the following goals during the first year of this project:
I. REDUCTION OF URANIUM (VI) BY CLOSTRIDIA.
In this study, we determined the ability of different Clostridia species to reduce U(VI) to
U(IV). Four strains were used in this study. Clostridium sp. (ATCC 53464), which was
1.0 isolated in this laboratory previously, C.
Clostridium sp. sphenoides (ATCC 19403), C. acetobutylicum
(ATCC 824) and C. pasteurianum (ATCC
0.8 7040) were obtained from the American Type
C. acetobutylicum Culture Collection.
0.6 We determined the growth profile of the
C. pasteurianum bacteria, head-space gas production, change in
5 pH of the medium, and identified the gaseous
0.4 and liquid metabolites. Among the strains
tested, Clostridium sp. grew the fastest and had
00.2 the highest cell density (Fig 1) in media
C. sphenoides containing glucose. Gas chromatography (GC)
analysis of the head space gases showed all
0 20 40 60 80 100 strains produced CO2 (50% ) and H2 (50%). The
Hours total gas production by the various isolates is
Figure 1. Growth of Clostridial isolates. shown in Figure 2. The pH of the medium
changed from near neutral to around pH 3 due
to production of organic acids. In contrast, the C. sphenoides cultured in Simmons Citrate

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FRANCIS, A.J.; GAO, W.; CHIDAMBARAM, D. & DODGE, C.J. MOLECULAR MECHANISM OF URANIUM REDUCTION BY CLOSTRIDIA AND ITS MANIPULATION., report, November 16, 2006; [Upton, New York]. (digital.library.unt.edu/ark:/67531/metadc881783/m1/3/ocr/: accessed November 13, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.

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