title: Microbial community responses to organophosphate substrate additions in contaminated subsurface sediments.
abstract: BACKGROUND
  Radionuclide- and heavy metal-contaminated subsurface sediments remain a legacy of Cold War nuclear weapons research and recent nuclear power plant failures. Within such contaminated sediments, remediation activities are necessary to mitigate groundwater contamination. A promising approach makes use of extant microbial communities capable of hydrolyzing organophosphate substrates to promote mineralization of soluble contaminants within deep subsurface environments.
  
  
  RESULTS
  Uranium-contaminated sediments from the U.S. Department of Energy Oak Ridge Field Research Center (ORFRC) Area 2 site were used in slurry experiments to identify microbial communities involved in hydrolysis of 10 mM organophosphate amendments [i.e., glycerol-2-phosphate (G2P) or glycerol-3-phosphate (G3P)] in synthetic groundwater at pH 5.5 and pH 6.8. Following 36 day (G2P) and 20 day (G3P) amended treatments, maximum phosphate (PO4(3-)) concentrations of 4.8 mM and 8.9 mM were measured, respectively. Use of the PhyloChip 16S rRNA microarray identified 2,120 archaeal and bacterial taxa representing 46 phyla, 66 classes, 110 orders, and 186 families among all treatments. Measures of archaeal and bacterial richness were lowest under G2P (pH 5.5) treatments and greatest with G3P (pH 6.8) treatments. Members of the phyla Crenarchaeota, Euryarchaeota, Bacteroidetes, and Proteobacteria demonstrated the greatest enrichment in response to organophosphate amendments and the OTUs that increased in relative abundance by 2-fold or greater accounted for 9%-50% and 3%-17% of total detected Archaea and Bacteria, respectively.
  
  
  CONCLUSIONS
  This work provided a characterization of the distinct ORFRC subsurface microbial communities that contributed to increased concentrations of extracellular phosphate via hydrolysis of organophosphate substrate amendments. Within subsurface environments that are not ideal for reductive precipitation of uranium, strategies that harness microbial phosphate metabolism to promote uranium phosphate precipitation could offer an alternative approach for in situ sequestration.
authors.affiliation: Department of Biological Sciences, University of Alabama, Tuscaloosa, Alabama, United States of America.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Martinez
authors.affiliation: Earth Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States of America.
authors.forename: Cindy H
authors.initials: CH
authors.lastname: Wu
authors.affiliation: Department of Biological Sciences, University of Alabama, Tuscaloosa, Alabama, United States of America.
authors.forename: Melanie J
authors.initials: MJ
authors.lastname: Beazley
authors.affiliation: Earth Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States of America.
authors.forename: Gary L
authors.initials: GL
authors.lastname: Andersen
authors.affiliation: Earth Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States of America.
authors.forename: Mark E
authors.initials: ME
authors.lastname: Conrad
authors.affiliation: Department of Civil and Environmental Engineering, University of Tennessee, Knoxville, Tennessee, United States of America.
authors.forename: Terry C
authors.initials: TC
authors.lastname: Hazen
authors.affiliation: School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia, United States of America.
authors.forename: Martial
authors.initials: M
authors.lastname: Taillefert
authors.affiliation: Department of Biological Sciences, University of Alabama, Tuscaloosa, Alabama, United States of America.
authors.forename: Patricia A
authors.initials: PA
authors.lastname: Sobecky
mesh_terms: D001105:Archaea / Q000166:cytology / Q000378:metabolism*; D001419:Bacteria / Q000166:cytology / Q000378:metabolism*; D001673:Biodegradation, Environmental; D019015:Geologic Sediments / Q000737:chemistry*; D006868:Hydrolysis; D010755:Organophosphates / Q000737:chemistry* / Q000378:metabolism*; D012995:Solubility; D014501:Uranium / Q000737:chemistry* / Q000378:metabolism*; D014874:Water Pollutants, Chemical / Q000737:chemistry / Q000378:metabolism
chemical_list: D010755:Organophosphates; D014874:Water Pollutants, Chemical; D014501:Uranium