title: Microbial populations stimulated for hexavalent uranium reduction in uranium mine sediment.
abstract: Uranium-contaminated sediment and water collected from an inactive uranium mine were incubated anaerobically with organic substrates. Stimulated microbial populations removed U almost entirely from solution within 1 month. X-ray absorption near-edge structure analysis showed that U(VI) was reduced to U(IV) during the incubation. Observations by transmission electron microscopy, selected area diffraction pattern analysis, and energy-dispersive X-ray spectroscopic analysis showed two distinct types of prokaryotic cells that precipitated only a U(IV) mineral uraninite (UO(2)) or both uraninite and metal sulfides. Prokaryotic cells associated with uraninite and metal sulfides were inferred to be sulfate-reducing bacteria. Phylogenetic analysis of 16S ribosomal DNA obtained from the original and incubated sediments revealed that microbial populations were changed from microaerophilic Proteobacteria to anaerobic low-G+C gram-positive sporeforming bacteria by the incubation. Forty-two out of 94 clones from the incubated sediment were related to sulfate-reducing Desulfosporosinus spp., and 23 were related to fermentative Clostridium spp. The results suggest that, if in situ bioremediation were attempted in the uranium mine ponds, Desulfosporosinus spp. would be a major contributor to U(VI) and sulfate reduction and Clostridium spp. to U(VI) reduction.
authors.affiliation: Department of Geology and Geophysics, University of Wisconsin-Madison, Madison, WI 53706, USA. yohey@jamstec.go.jp
authors.forename: Yohey
authors.initials: Y
authors.lastname: Suzuki
authors.forename: Shelly D
authors.initials: SD
authors.lastname: Kelly
authors.forename: Kenneth M
authors.initials: KM
authors.lastname: Kemner
authors.forename: Jillian F
authors.initials: JF
authors.lastname: Banfield
mesh_terms: D000693:Anaerobiosis; D001421:Bacteria, Anaerobic / Q000145:classification* / Q000235:genetics / Q000378:metabolism; D003470:Culture Media; D004275:DNA, Ribosomal / Q000032:analysis; D017753:Ecosystem; D005618:Fresh Water / Q000737:chemistry / Q000382:microbiology*; D019015:Geologic Sediments / Q000382:microbiology*; D006094:Gram-Positive Bacteria / Q000145:classification / Q000378:metabolism; D008906:Mining; D010084:Oxidation-Reduction; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017422:Sequence Analysis, DNA; D013431:Sulfates / Q000378:metabolism; D014501:Uranium / Q000378:metabolism*; D014877:Water Pollution, Chemical
chemical_list: D003470:Culture Media; D004275:DNA, Ribosomal; D012336:RNA, Ribosomal, 16S; D013431:Sulfates; D014501:Uranium