Environmental Engineering Reference
In-Depth Information
Recently, we have been extending these laboratory and well-controlled pure
culture studies to the field by studying uranium immobilization using biofilms
of indigenous microorganisms grown on sediments from the Hanford 300 Area.
Uranium accumulated in biofilms of the lactate-stimulated naturally occurring
bacteria in this system with less efficiency than what we expected on the basis
of previous pure-culture studies using SRB biofilms grown on glass slides or
carbonate-bearing minerals.
As the ubiquitous growth pattern of indigenous microorganisms in soils and
water-sediment interfaces at contaminated sites, biofilms play an important role in
the
in situ
bioremediation of uranium. The metabolic activity of cells in biofilms,
differing from that of suspended cells, affects the abiotic and redox reactions con-
trolling the mobility of U(VI) in the environment. The complex biotic, abiotic and
redox conditions in biofilms pose challenges in predicting the mobility of uranium
because uranium immobilization in biofilms with heterogeneous local conditions
can be significantly different from that in bulk conditions. In order to efficiently and
sustainably harness indigenous heterogeneous biofilms to immobilize uranium at
contaminated sites, much more research work will be needed to elucidate the com-
plex interactions among uranium, biofilms, and various redox-sensitive minerals
during
in situ
uranium bioremediation.
Acknowledgements
This research was supported by the Office of Science (BER), U.S.
Department of Energy, Grant No. DE-FG02-08ER64560. We thank Raice Ahmad for provid-
ing data on uranium immobilization using
S. oneidensis
MR-1 biofilms and Alice Dohnalkova
for HRTEM and SEM biofilm images. We also wish to thank anonymous reviewers for review-
ing our manuscript. A portion of this research was performed at the Environmental Molecular
Sciences Laboratory (EMSL), a national scientific user facility sponsored by the U.S. Department
of Energy's Office of Biological and Environmental Research and located at Pacific Northwest
National Laboratory (PNNL). Beyenal acknowledges Professors Zbigniew Lewandowski and
Brent Peyton, Montana State University and DOE (Grants #DE-FG03-98ER62630/A001 and
#DE-FG03-01ER63270) for his past training on biofilms and uranium.
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