title: Field evidence of selenium bioreduction in a uranium-contaminated aquifer.
abstract: Removal of selenium from groundwater was documented during injection of acetate into a uranium-contaminated aquifer near Rifle, Colorado (USA). Bioreduction of aqueous selenium to its elemental form (Se0) concentrated it within mineralized biofilms affixed to tubing used to circulate acetate-amended groundwater. Scanning and transmission electron microscopy revealed close association between Se0 precipitates and cell surfaces, with Se0 aggregates having a diameter of 50-60 nm. Accumulation of Se0 within biofilms occurred over a three-week interval at a rate of c. 9 mg Se0 m(-2) tubing day(-1). Removal was inferred to result from the activity of a mixed microbial community within the biofilms capable of coupling acetate oxidation to the reduction of oxygen, nitrate and selenate. Phylogenetic analysis of the biofilm revealed a community dominated by strains of Dechloromonas sp. and Thauera sp., with isolates exhibiting genetic similarity to the latter known to reduce selenate to Se0. Enrichment cultures of selenate-respiring microorganisms were readily established using Rifle site groundwater and acetate, with cultures dominated by strains closely related to D. aromatica (96-99% similarity). Predominance of Dechloromonas sp. in recovered biofilms and enrichments suggests this microorganism may play a role in the removal of selenium oxyanions present in Se-impacted groundwaters and sediments.
authors.affiliation: Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA. khwilliams@lbl.gov
authors.forename: Kenneth H
authors.initials: KH
authors.lastname: Williams
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Wilkins
authors.forename: A Lucie
authors.initials: AL
authors.lastname: N'Guessan
authors.forename: Bruce
authors.initials: B
authors.lastname: Arey
authors.forename: Elena
authors.initials: E
authors.lastname: Dodova
authors.forename: Alice
authors.initials: A
authors.lastname: Dohnalkova
authors.forename: Dawn
authors.initials: D
authors.lastname: Holmes
authors.forename: Derek R
authors.initials: DR
authors.lastname: Lovley
authors.forename: Philip E
authors.initials: PE
authors.lastname: Long
mesh_terms: D000085:Acetates / Q000378:metabolism; D020562:Betaproteobacteria / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D001673:Biodegradation, Environmental; D018441:Biofilms / Q000254:growth & development; D003120:Colorado; D060587:Groundwater / Q000737:chemistry / Q000382:microbiology; D006801:Humans; D059013:Microbial Consortia / Q000502:physiology; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000145:classification / Q000235:genetics*; D064586:Selenic Acid; D012643:Selenium / Q000378:metabolism*; D018036:Selenium Compounds / Q000378:metabolism; D020628:Thauera / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D014501:Uranium / Q000378:metabolism*; D014874:Water Pollutants, Chemical / Q000378:metabolism*
chemical_list: D000085:Acetates; D012336:RNA, Ribosomal, 16S; D018036:Selenium Compounds; D014874:Water Pollutants, Chemical; D014501:Uranium; D012643:Selenium; D064586:Selenic Acid; D010100:Oxygen