MOLECULAR MECHANISM OF URANIUM REDUCTION BY CLOSTRIDIA AND ITS MANIPULATION. Page: 4 of 7
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20 40 60
Figure 2. Headspace gas producti
300 400 500 600
Figure 3. UV-vis spectra of U(VI)
by Clostridium sp.
Table 1. Rate of U(VI) reduction by C
Strain U(VI) reduction
(pM hr-lpg-I protein)
Clostridium sp. 0.1
C. acetobutylicum 0.025
C. pasteurianum 0.01
C. sphenoides 0.05
II. BIOCHEMICAL BASIS OF URANIUM
REDUCTION BY CLOSTRIDIA
In this study, we demonstrate that the
hydrogenase enzyme plays an important role in
both uranium (VI) and iron (III) reduction by
Clostridium sp. When hydrogen gas (H2) was
provided in the headspace of the serum bottle,
either uranium (VI) or iron (III) reduction occurred
medium showed a slight pH increase due to
p. degradation of citric acid. High performance liquid
chromatography (HPLC) analysis of bacterial
fermentation products showed that all strains tested
cum produced acetic acid. In addition, Clostridium sp., C.
acetobutylicum and C. pasteurianum produced
isobutyric acid, while C. sphenoides produced butyric
acid and oxalacetic acid.
num Both uranium (VI)-citrate and uranium (VI)-
nitrate were reduced by the four isolates tested,
S indicating that uranium (VI) complexation with
80 100 citrate did not affect the rate or extent of bacterial
reduction. The pH of the culture did however have a
significant effect on uranium reduction, with pH 5-6
on being the optimal pH for uranium (VI) reduction in
most cases. Clostridium sp. showed the strongest
ability to reduce uranium and was less affected by
culture pH compared with other strains. Upon
addition of U(VI), Clostridium sp. immediately
reduced uranium with over 60% uranium reduction
within 8 hours and 90% reduction in 24 hours. The
reduction of U (IV) to U (VI) was confirmed using
UV-vis spectra (Fig 3). Uranium (VI) reduction by all
other strains occurred at a slower rate even under
Our results showed that while the ability to
reduce uranium is a common phenomenon among
Clostridia, the differences in their ability to reduce it
700 800 is evident among the strains tested. Clostridium sp.
i) showed the highest uranium reduction which may
partially be attributed to its adaptation to harsh
reduction environmental conditions such as low pH, as well as
its capacity to rapidly ferment glucose. Under optimal
conditions, the estimated uranium reduction rate of
each strain is shown in Table 1.
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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]. (https://digital.library.unt.edu/ark:/67531/metadc881783/m1/4/: accessed March 23, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.