Microbial communities in contaminated sediments, associated with bioremediation of uranium to submicromolar levels.
Microbial enumeration, 16S rRNA gene clone libraries, and chemical analysis were used to evaluate the in situ biological reduction and immobilization of uranium(VI) in a long-term experiment (more than 2 years) conducted at a highly uranium-contaminated site (up to 60 mg/liter and 800 mg/kg solids) of the U.S. Department of Energy in Oak Ridge, TN. Bioreduction was achieved by conditioning groundwater above ground and then stimulating growth of denitrifying, Fe(III)-reducing, and sulfate-reducing bacteria in situ through weekly injection of ethanol into the subsurface. After nearly 2 years of intermittent injection of ethanol, aqueous U levels fell below the U.S. Environmental Protection Agency maximum contaminant level for drinking water and groundwater (<30 microg/liter or 0.126 microM). Sediment microbial communities from the treatment zone were compared with those from a control well without biostimulation. Most-probable-number estimations indicated that microorganisms implicated in bioremediation accumulated in the sediments of the treatment zone but were either absent or in very low numbers in an untreated control area. Organisms belonging to genera known to include U(VI) reducers were detected, including Desulfovibrio, Geobacter, Anaeromyxobacter, Desulfosporosinus, and Acidovorax spp. The predominant sulfate-reducing bacterial species were Desulfovibrio spp., while the iron reducers were represented by Ferribacterium spp. and Geothrix spp. Diversity-based clustering revealed differences between treated and untreated zones and also within samples of the treated area. Spatial differences in community structure within the treatment zone were likely related to the hydraulic pathway and to electron donor metabolism during biostimulation.
Cardenas
Erick
E
Center for Microbial Ecology, Michigan State University, East Lansing, MI 48824, USA.
Wu
Wei-Min
WM
Leigh
Mary Beth
MB
Carley
Jack
J
Carroll
Sue
S
Gentry
Terry
T
Luo
Jian
J
Watson
David
D
Gu
Baohua
B
Ginder-Vogel
Matthew
M
Kitanidis
Peter K
PK
Jardine
Philip M
PM
Zhou
Jizhong
J
Criddle
Craig S
CS
Marsh
Terence L
TL
Tiedje
James M
JM
D001419:Bacteria / Q000145:classification* / Q000235:genetics* / Q000302:isolation & purification; D001673:Biodegradation, Environmental; D044822:Biodiversity; D016000:Cluster Analysis; D015169:Colony Count, Microbial; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004275:DNA, Ribosomal / Q000737:chemistry / Q000235:genetics; D000431:Ethanol / Q000378:metabolism; D020459:Genes, rRNA; D019015:Geologic Sediments / Q000382:microbiology*; D008969:Molecular Sequence Data; D010802:Phylogeny; D012329:RNA, Bacterial / Q000235:genetics; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017422:Sequence Analysis, DNA; D012689:Sequence Homology, Nucleic Acid; D014481:United States; D014501:Uranium / Q000378:metabolism*
D004269:DNA, Bacterial; D004275:DNA, Ribosomal; D012329:RNA, Bacterial; D012336:RNA, Ribosomal, 16S; D000431:Ethanol; D014501:Uranium