Environmental Engineering Reference
In-Depth Information
Table 1.1
Bacteria reported to reduce U(VI) to U(IV)
Bacterial species
Descriptions/comments
References
Anaeromyxobacter
dehalogenans
Fumarate-grown cells reduced U(VI)-U(IV). Hydrogen was required as an electron donor
and could not be replaced by acetate; the addition of nitrate caused reoxidation, but
reduction resumed following consumption of the N-oxyanions. Reduction was inhibited
by Fe(III) citrate or citrate; U(VI) reduction proceeded to completion at a much lower rate
with amorphous Fe(III) oxide. No inhibition by fumarate or 2-chlorophenol was
observed, and both were consumed concomitantly with U(VI). The coupling of U(VI)
reduction to cell growth was established by monitoring the increase in 16S rRNA gene
copy numbers using qPCR.
[112, 113]
Cellulomonas
sp.
The oxidation of lactate or other unknown electron donors in the absence of lactate was
coupled to U(VI) reduction. The reduction rate was slow: at least 150 h was required to
reduce 0.2 mM U(VI) at a concentration of 500 mg/L total cell protein.
[114]
Clostridium acetobutylicum
Uranyl-nitrate, -acetate, and -citrate complexes were reduced. The mechanisms remain
unclear; optimizing the conditions for fermentation resulted in better U(VI) reduction.
[115, 116,
117]
Clostridium pasteurianum
Clostridium
sp.
Clostridium sphenoides
Deinococcus radiodurans
Reduction of U(VI) occurred in the presence of humic acid analog
anthraquinone-2,6-disulfonate; a recombinant strain harboring phoN, a gene encoding a
nonspecific acid phosphatase, exhibited a high uranium precipitation ability even after
exposure to 6 kGy of
60
Co gamma irradiation.
[118, 119]
Desulfotomaculum
reducens
This was the first sulfate-reducing bacterium that could grow with U(VI) as the sole
electron acceptor; it shared physiological properties with both the sulfate-reducing and
metal-reducing groups of bacteria.
[120]
Desulfosporosinus
sp.
Desulfosporosinus orientis
No U(VI) reduction occurred in cell suspensions with 0.25% Na-bicarbonate or 0.85%
NaCl; there was enzymatic reduction in cell suspensions depleted in bicarbonate and
NaCl. U(VI) reduction was inhibited when 1 mM CuCl
2
was added to the cell
suspensions.
[43]
Desulfosporosinus
GBSRB4.2
This acid-tolerant sulfate-reducing bacterium enzymatically reduced U(VI) in acidic
solutions (pH 4.2); it reduced U(VI) in groundwater more rapidly at pH 4.4 than at pH 7.1.
[121]
