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Title: Microbial Uranium Immobilization Independent of Nitrate Reduction

Abstract

At many uranium processing and handling facilities, including sites in the U.S. Department of Energy (DOE) complex, high levels of nitrate are present as co-contamination with uranium in groundwater. The daunting prospect of complete nitrate removal prior to the reduction of uranium provides a strong incentive to explore bioremediation strategies that allow for uranium bioreduction and stabilization in the presence of nitrate. Typical in-situ strategies involving the stimulation of metal-reducing bacteria are hindered by low pH environments at this study site and require that the persistent nitrate must first and continuously be removed or transformed prior to uranium being a preferred electron acceptor. This project investigates the possibility of stimulating nitrate-indifferent, pH-tolerant microorganisms to achieve bioreduction of U(VI) despite nitrate persistence. Successful enrichments from U-contaminated sediments demonstrated nearly complete reduction of uranium with very little loss of nitrate from pH 4.9-5.6 using methanol or glycerol as a carbon source. Higher pH enrichments also demonstrated similar U reduction capacity with 5-30% nitrate loss within one week. Bacterial 16S rRNA genes were amplified from uranium-reducing enrichments (pH 5.7-6.7) and sequenced. Phylogenetic analyses classified the clone sequences into four distinct clusters. Data from sequencing and T-RFLP profiles indicated that the majority of themore » microorganisms stimulated by these enrichment conditions consisted of low G+C Gram-positive bacteria most closely related to Clostridium and Clostridium-like organisms. This research demonstrates that the stimulation of a natural microbial community to immobilize U through bioreduction is possible without the removal of nitrate.« less

Authors:
 [1];  [2];  [2];  [1];  [1]
  1. ORNL
  2. Florida State University
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
961553
DOE Contract Number:  
DE-AC05-00OR22725
Resource Type:
Journal Article
Resource Relation:
Journal Name: Environmental Microbiology; Journal Volume: 9; Journal Issue: 9
Country of Publication:
United States
Language:
English
Subject:
10 SYNTHETIC FUELS; BACTERIA; BINDING ENERGY; BIOREMEDIATION; CAPACITY; CARBON SOURCES; CLOSTRIDIUM; ELECTRONS; GENES; GLYCEROL; METHANOL; MICROORGANISMS; NITRATES; REMOVAL; SEDIMENTS; STABILIZATION; STIMULATION; URANIUM; VALENCE; Uranium; bioremediation; nitrate

Citation Formats

Madden, Andrew, Smith, April, Balkwill, Dr. David, Fagan, Lisa Anne, and Phelps, Tommy Joe. Microbial Uranium Immobilization Independent of Nitrate Reduction. United States: N. p., 2007. Web. doi:10.1111/j.1462-2920.2007.01347.x.
Madden, Andrew, Smith, April, Balkwill, Dr. David, Fagan, Lisa Anne, & Phelps, Tommy Joe. Microbial Uranium Immobilization Independent of Nitrate Reduction. United States. doi:10.1111/j.1462-2920.2007.01347.x.
Madden, Andrew, Smith, April, Balkwill, Dr. David, Fagan, Lisa Anne, and Phelps, Tommy Joe. Mon . "Microbial Uranium Immobilization Independent of Nitrate Reduction". United States. doi:10.1111/j.1462-2920.2007.01347.x.
@article{osti_961553,
title = {Microbial Uranium Immobilization Independent of Nitrate Reduction},
author = {Madden, Andrew and Smith, April and Balkwill, Dr. David and Fagan, Lisa Anne and Phelps, Tommy Joe},
abstractNote = {At many uranium processing and handling facilities, including sites in the U.S. Department of Energy (DOE) complex, high levels of nitrate are present as co-contamination with uranium in groundwater. The daunting prospect of complete nitrate removal prior to the reduction of uranium provides a strong incentive to explore bioremediation strategies that allow for uranium bioreduction and stabilization in the presence of nitrate. Typical in-situ strategies involving the stimulation of metal-reducing bacteria are hindered by low pH environments at this study site and require that the persistent nitrate must first and continuously be removed or transformed prior to uranium being a preferred electron acceptor. This project investigates the possibility of stimulating nitrate-indifferent, pH-tolerant microorganisms to achieve bioreduction of U(VI) despite nitrate persistence. Successful enrichments from U-contaminated sediments demonstrated nearly complete reduction of uranium with very little loss of nitrate from pH 4.9-5.6 using methanol or glycerol as a carbon source. Higher pH enrichments also demonstrated similar U reduction capacity with 5-30% nitrate loss within one week. Bacterial 16S rRNA genes were amplified from uranium-reducing enrichments (pH 5.7-6.7) and sequenced. Phylogenetic analyses classified the clone sequences into four distinct clusters. Data from sequencing and T-RFLP profiles indicated that the majority of the microorganisms stimulated by these enrichment conditions consisted of low G+C Gram-positive bacteria most closely related to Clostridium and Clostridium-like organisms. This research demonstrates that the stimulation of a natural microbial community to immobilize U through bioreduction is possible without the removal of nitrate.},
doi = {10.1111/j.1462-2920.2007.01347.x},
journal = {Environmental Microbiology},
number = 9,
volume = 9,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}