Microbial activities in deep subsurface environments

Phelps, Tommy J.; Raione, E. G.; White, David C.; Fliermans, C.B.

doi:10.2172/666219

Cited by 8 publications

(8 citation statements)

References 6 publications

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“…Enrichments were prepared in sterile serum bottles (120 ml) with butyl rubber stoppers by adding 5 g of sediment, 5 ml of OR FRC groundwater, 10 ml of modified basal medium, NaNO 3 to a final concentration of ∼0.1%, 50 mM MOPS buffer at pHs from 5.4 to 6.2, with methanol or glycerol as electron donors at ∼7–30 mM. For each 1 l of media, the following were added: 945 ml of MilliQ water, 0.9 g of NaCl, 0.2 g of MgCl 2 ·6H 2 O, 1.0 g of NH 4 Cl, 0.5 g of east extract, 10 ml of ORNL trace mineral II solution (Phelps et al ., 1989), 1 ml of ORNL vitamin solution (Phelps et al ., 1989), 0.1 ml of 0.1% rezasurin and 0.2 ml of 1.5 M MOPS buffer. Media were prepared anaerobically by boiling and cooling under N 2 , followed by transfer of 10 ml to 28 ml pressure tubes under N 2 flow.…”

Section: Methodsmentioning

confidence: 99%

Microbial uranium immobilization independent of nitrate reduction

Madden

Smith

Balkwill

et al. 2007

Environmental Microbiology

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At many uranium processing and handling facilities, including sites in the US 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 and require that the persistent nitrate must first and continuously be removed or transformed prior to uranium being a preferred electron acceptor. This work investigated the possibility of stimulating nitrate-indifferent, pH-tolerant microorganisms to achieve bioreduction of U(VI) despite nitrate persistence. Enrichments from U-contaminated sediments demonstrated nearly complete reduction of uranium with very little loss of nitrate from pH 5.7-6.2 using methanol or glycerol as a carbon source. Bacterial 16S rRNA genes were amplified from uranium-reducing enrichments (pH 5.7-6.2) and sequenced. Phylogenetic analyses classified the clone sequences into four distinct clusters. Data from sequencing and terminal-restriction fragment length polymorphism (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.

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Section: Methodsmentioning

confidence: 99%

Microbial uranium immobilization independent of nitrate reduction

Madden

Smith

Balkwill

et al. 2007

Environmental Microbiology

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“…Over the next 40 years, various investigators came to similar conclusions concerning the importance of microorganisms in determining groundwater geochemistry (Cedarstrom 1946;Gurevich 1962). However, not until methods for aseptic sampling of subsurface sediments were developed (Dunlap et al 1977;Ghiorse and Balkwill 1983;Wilson et al 1983;Phelps et al 1989) and comprehensive evaluations of microorganisms present were made (Chapelle et al 1987(Chapelle et al , 1988Fredrickson et al 1989Fredrickson et al , 1991 did the effects of microbial metabolism on groundwater geochemistry become widely known.…”

Section: Introductionmentioning

confidence: 99%

The significance of microbial processes in hydrogeology and geochemistry

Chapelle¹

2000

Hydrogeology Journal

103

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Microbial processes affect the chemical composition of groundwater and the hydraulic properties of aquifers in both contaminated and pristine groundwater systems. The patterns of water-chemistry changes that occur depend upon the relative abundance of electron donors and electron acceptors. In many pristine aquifers, where microbial metabolism is limited by the availability of electron donors (usually organic matter), dissolved inorganic carbon (DIC) accumulates slowly along aquifer flow paths and available electron acceptors are consumed sequentially in the order dissolved oxygen > nitrate > Fe(III) > sulfate > CO 2 (methanogenesis). In aquifers contaminated by anthropogenic contaminants, an excess of available organic carbon often exists, and microbial metabolism is limited by the availability of electron acceptors. In addition to changes in groundwater chemistry, the solid matrix of the aquifer is affected by microbial processes. The production of carbon dioxide and organic acids can lead to increased mineral solubility, which can lead to the development of secondary porosity and permeability. Conversely, microbial production of carbonate, ferrous iron, and sulfide can result in the precipitation of secondary calcite or pyrite cements that reduce primary porosity and permeability in groundwater systems.

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“…Since then, culturable microorganisms have been detected in both saturated and unsaturated subsurface environments, at depths ranging to 2.7 km below land surface, and at temperatures up to 60°C. These organisms have also been found in a wide range of geologically distinct materials, including sandy Atlantic Coastal Plain sediments [2–10], unwelded volcanic tuffs [11–13], basalts and clay/silt interbeds [14], fluvial sands and gravels [14–16], lacustrine sediments [16], paleosols [14–17], Triassic siltstones [18, 19], granitic rocks and groundwater [20–22], and deep clays from a mine gallery [23]. Interest in subsurface microorganisms has increased rapidly, as investigators have come to understand that they are widely distributed in terrestrial environments and are likely to influence geochemical processes, the fate and/or transport of environmental contaminants, and the quality of groundwater.…”

Section: Introductionmentioning

confidence: 99%

Phylogenetic characterization of bacteria in the subsurface microbial culture collection

et al. 1997

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The Subsurface Microbial Culture Collection (SMCC) was established by the U.S. Dept. of Energy (DOE) and contains nearly 10,000 strains of microorganisms (mostly bacteria) isolated from terrestrial subsurface environments. Selected groups of bacterial isolates from three sample sites situated above geochemically and hydrologically different subsurface environments have been characterized by phylogenetic analysis of 16S ribosomal RNA (rRNA) gene nucleotide sequences. Among these isolates were members of six major phylogenetic groups of bacteria: the high-G+C and low-G+C Gram-positive bacteria; the alpha-, beta-, and gamma-subdivisions of the Proteobacteria; and the Flexibacter/Cytophaga/Bacteroides group. A small number of the SMCC strains may be members of new bacterial genera, but most of them could be placed with reasonable confidence into more than 35 previously described genera. The majority of the Gram-positive isolates were species of Arthrobacter, Bacillus, or Streptococcus, whereas Acinetobacter, Comamonas, Pseudomonas, Sphingomonas, and Variovorax were among the most frequently encountered Gram-negative genera. A high proportion of the strains were placed in fewer than 10 genera, implying that there is substantial duplication within the SMCC at the genus level. When groups of isolates assigned to Acinetobacter, Arthrobacter, or Sphingomonas were analyzed in more detail, however, it was found that each group consisted of subgroups of strains that probably differed at the species level. Restriction endonuclease analysis (applied to the strains from one sample site) indicated that additional diversity was present at the strain level. Most of the SMCC isolates assigned to some genera (e.g., Acinetobacter) were very closely related to previously described species in those genera, but most of the isolates assigned to other genera (e.g., Arthrobacter and Sphingomonas) appeared (or were shown) to be new species, thereby indicating that a reasonable amount of novelty is present within the SMCC at the species level.

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Microbial activities in deep subsurface environments

Cited by 8 publications

References 6 publications

Microbial uranium immobilization independent of nitrate reduction

Microbial uranium immobilization independent of nitrate reduction

The significance of microbial processes in hydrogeology and geochemistry

Phylogenetic characterization of bacteria in the subsurface microbial culture collection

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