| 1. |
- Anderson, Craig, 1976, et al.
(författare)
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Autoradiographic comparisons of radionuclide adsorption between subsurface anaerobic biofilms and granitic host rocks
- 2006
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Ingår i: Geomicrobiology Journal. - : Informa UK Limited. - 0149-0451 .- 1521-0529. ; 23:1, s. 15-29
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Tidskriftsartikel (refereegranskat)abstract
- In high level nuclear waste repositories, the host rock is considered to be an important barrier to radionuclide migration by adsorbing metals at fluid rock interfaces. In granitic rock environments the surfaces of hydraulically conductive fractures are covered with mixed community biofilms. Biofilms were grown in situ on glass and rock surfaces in high pressure flow cells using groundwater sourced from a borehole 450 meters below sea level in the Aspo hard rock laboratory, Sweden. Scanning electron microscopy (SEM), epifluorescence microscopy and energy dispersive X-Ray spectroscopy (EDS) revealed monolayer biofilms consisting of up to 2 x 10(4) bacteria/mm(2) surrounded by an extensive extracellular matrix and carbonate precipitates that covered
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| 2. |
- Eriksson, Sara, 1974, et al.
(författare)
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Indicators of petroleum hydrocarbon biodegradation in anaerobic granitic groundwater
- 2006
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Ingår i: Geomicrobiology Journal. - : Informa UK Limited. - 0149-0451 .- 1521-0529. ; 23:1, s. 45-58
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to find indicators of petroleum biodegradation in granitic groundwater. Both pristine and contaminated groundwaters from boreholes around petroleum storage vaults located approximately 40 m below the surface in granite and with storage capacities of up to 120,000 m(3) were sampled. Total numbers of microorganisms, "most probable numbers" (MPN) of anaerobic bacteria, and chemical indications of microbial activity were determined in the groundwater. Hydrocarbon contaminants and metabolites were detected using gas chromatographymass spectrometry (GC-MS). In contaminated groundwater, the total number of microorganisms was 2-4 x 10(6) ml(-1), which was significantly higher than the 6 x 10(4) ml(-1) found in pristine groundwater. This microbial abundance was also reflected in the MPN analysis. Up to 7 x 10(4) nitrate-, 2 x 10(3) iron-, and 3 x 10(4) sulfate-reducing bacteria were detected in contaminated groundwaters. In such groundwaters, depletion of anaerobic electron acceptors and detection of reduced species could be established. We also proposed using a high alkalinity/hardness of water quota (A/H quota) as an indicator of microbial activity. In contaminated groundwaters the A/H quota averaged 2.8, while in pristine groundwater the same was only 1.3. Moreover, the presence of 20 oxidized petroleum hydrocarbons, i.e., putative metabolites of which 9 were strictly intracellular, was detected in the contaminated groundwaters. Phylogenetic neighbor-joining analysis of 16S rRNA genes provided information about the bacterial communities. The bacteria in contaminated groundwater were found to be strikingly similar to bacteria in other hydrocarbon-contaminated environments.
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| 3. |
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| 4. |
- Johnsson, Anna, 1975, et al.
(författare)
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Solid-aqueous phase partitioning of radionuclides by complexing compounds excreted by subsurface bacteria
- 2006
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Ingår i: Geomicrobiology Journal. - : Informa UK Limited. - 0149-0451 .- 1521-0529. ; 23(8), s. 621-630
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Tidskriftsartikel (refereegranskat)abstract
- Radionuclides are present in numerous aerobic and anaerobic subsurface environments due to nuclear weapons testing, leakage from process and storage facilities, and discharge of radioactive waste. The partitioning of radionuclides between liquid and solid phases by complexing compounds excreted by subsurface bacteria was studied. The solid-aqueous phase partitioning of pico- to submicromolar amounts of 59 Fe, 147 Pm, 234 Th, and 241 Am was analyzed in the presence of quartz sand and exudates from three species of subsurface bacteria: Pseudomonas fluorescens, Pseudomonas stutzeri, and Shewanella putrefaciens. All were grown under aerobic conditions, and P. stutzeri and S. putrefaciens were grown under anaerobic conditions as well. The supernatants of the aerobic and anaerobic cultures were collected and radionuclide was added. Quartz sand, with a Brunauer, Emmett, and Teller (BET) surface area of 0.1 m 2 g -1 , was added to the supernatant radionuclide mix, and the pH was adjusted to approximately 8. After centrifuging, the amount of radionuclide in the liquid phase of the samples and controls was analyzed using scintillation. Relative to the control, aerobic supernatants maintained more than 50% of the added 59 Fe, 234 Th, and 241 Am. The highest amount of metal present in the liquid phase of the anaerobic supernatants was found in the case of 241 Am, with 40% more 241 Am in samples than in controls. Both aerobic and anaerobic supernatants tested positive for complexing compounds when analyzed using the Chrome Azurol S assay. The great amounts of radionuclides in the liquid phases of samples were likely due to complexation with such compounds. Bacterially excreted complexing compounds hence seem able to influence the solid-aqueous phase partitioning of radionuclides. This could influence the mobility of radionuclides in contaminated subsurface environments.
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| 5. |
- Kalinowski, Birgitta E., et al.
(författare)
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Microbial mobilization of uranium from shale mine waste
- 2006
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Ingår i: Geomicrobiology Journal. - : Informa UK Limited. - 0149-0451 .- 1521-0529. ; 23:3-4, s. 157-164
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Tidskriftsartikel (refereegranskat)abstract
- The alum shale in the Billingen area in southern Sweden was mined in Ranstad for 5 years during the 1960s. The crushed tailings (processed and unprocessed) were left behind when the Ranstad mine was closed that has caused leaching of metals to the surroundings. The siderophore producing bacterium Pseudomonas fluorescens (sp, SE Sweden) was grown in batch cultures for 5 to 8 days with naturally weathered (unprocessed) uranium ore (0.0029% U by weight), kolm (0.52% U by weight) and acid-leached ore (0.0099% U by weight) in chemically defined media (unbuffered and buffered). Pseudomonas fluorescens grown with ore and unbuffered medium changed the pH from 4.7 to 9.3 and leached out 0.016 to 0.9% (normalized to surface area) of the total amount of U from the different ores. Incubation of the acid-leached ore with bacteria in buffered medium leached out 0.04% of the total U. Uranium was leached out selectively at all conditions, but this could be a pH effect, as pH increased at the same time as the U concentrations did. The observed release of Fe was most likely attributed to the production of microbial siderophores (Fe3+ specific chelators) since Fe3+ has a low solubility at pH > 4. As siderophores contain a number of chelating groups they may still function as complexators even in partly degraded form also for other metals than Fe. Thus, the production of microbial chelators could contribute to the elevated metal concentrations in the drainage water from the closed Ranstad mine, as abiotic processes cannot fully explain these high metal concentrations. In the extension: ligand promoted leaching of toxic elements could also be the key to bioremediation as there is a need for nontoxic cleanup methods for metal contaminated sites.
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| 6. |
- Karnachuk, Olia V, et al.
(författare)
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Sulfate reduction potential in sediments in the Norilsk mining area, northern Siberia
- 2005
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Ingår i: Geomicrobiology Journal. - Philadelphia : Taylor & Francis. - 0149-0451 .- 1521-0529. ; 22:1-2, s. 11-25
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of this study was to characterize the distribution and activity of sulfate-reducing bacteria in tailings and sediments impacted by effluents from mining and smelting operations in the Norilsk area in northern Siberia. The Norilsk mining complex involves three smelter operations, a hydrometallurgical plant, and extensive tailings areas located in the permafrost zone. Sulfate reduction rates measured with a (35)SO(4)(2-) tracer technique under various in-situ conditions ranged from 0.05 to 30 nmol S cm(-3) day(-1). Acetate and glucose addition greatly stimulated sulfate reduction, whereas lactate had less effect. The most pronounced stimulation of sulfate reduction (6.5-fold) was observed with phosphate amendment. Most-probable-number (MPN) counts of sulfate-reducing bacteria in media with glucose, ethanol, lactate, and acetate as electron donors were generally highest at around 10(7) cells ml(-1). The actual MPN counts varied with the sample, electron donor, and incubation conditions (pH 7.2 vs. pH 3.5; 28 degrees C vs. 4 degrees C). Enrichment cultures of sulfate-reducing bacteria were established from a sample that showed the highest rate of sulfate reduction. After multiple serial transfers, the dominant sulfate-reducers were identified by fluorescence in situ hybridization using genus and group-specific 16S rRNA-targeted oligonucleotide probes. Desulfobulbus spp. prevailed in ethanol and lactate enrichments and the Desulfosarcina-Desulfococcus group dominated in acetate and benzoate enrichments. Psychrophilic Desulfotalea-Desulfofustis and moderately psychrophilic Desulforhopalus spp. were identified in enrichments incubated at 4 degrees C, but they were also found in mesophilic enrichments.
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| 7. |
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| 9. |
- Polymanakou, Paraskevi, et al.
(författare)
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Organic Matter Preservation and Microbial Community Accumulations in Deep-Hypersaline Anoxic Basins
- 2007
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Ingår i: Geomicrobiology Journal. - : Informa UK Limited. - 0149-0451 .- 1521-0529. ; 24:1, s. 19-29
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Tidskriftsartikel (refereegranskat)abstract
- The Eastern Mediterranean Sea hosts several deep hypersaline anoxic basins (DHABs) such as the Bannock, L'Atalante, Discovery, and Urania which, due to strong salinity gradients, have a limited exchange with the overlying seawater. In the present study, a series of environmental variables associated with the origin and quality of organic matter were thoroughly investigated in an attempt to understand the function of these unique ecosystems. The redox potential of sediments collected from the brines as well as from reference sites varied from -136 to 543 mV and salinity varied from 38 to 380 psu. Principal component analysis of chemical characteristics, including salinity, redox potential, organic carbon and nitrogen content, and C/N ratio grouped the sediments into two major clusters according to their redox state. Aliphatic hydrocarbon analysis revealed that the organic matter in the DHABs was predominantly of terrestrial origin but there was also evidence for petroleum inputs and for organic matter of phototrophic origin. Phospholipid linked fatty acids (PLFA) which were employed to assess the composition of microbial communities were found in greater abundance in stations situated inside the anoxic basins providing also strong evidence for the presence of methanotrophs and sulfate reducers. These results may represent an enhanced preservation of organic matter and an accumulation of microorganisms in these extreme environments. Heterogeneity in microbial community fatty acid profiles was documented between the anoxic sediments and the oxic and suboxic stations. However there were no significant correlations between PLFA and organic matter parameters. Redox conditions appear to influence microbial community composition, highlighting the role of the redox state as a regulator of organic matter preservation and microbial community accumulations in these ancient hypersaline anoxic lakes.
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| 10. |
- Purvis, William O., et al.
(författare)
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Mineralization in Rust-coloured Acarospora
- 2008
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Ingår i: Geomicrobiology Journal. - : Informa UK Limited. - 0149-0451 .- 1521-0529. ; 25:3-4, s. 142-148
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Tidskriftsartikel (refereegranskat)abstract
- The upper cortex and extracellular hyphal wall matrix are mineralized in both rust-coloured Acarospora sinopica and the paler A. smaragdula 'f. subochracea' in the form of microgranular or microbotryoidal phases. Analysis confirmed the distinctive colours are not simply due to hydrated iron oxides, as previously believed, and suggests mixed sulphide and oxide phases with little crystallinity, as well as other elements arising from clay minerals are present. These aspects highlight the need for a more detailed study employing a range of micro-analytical techniques, including analytical TEM, which will allow mineral characterisation and localisation down to the nanometre scale.
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| 11. |
- Rosling, Anna
(författare)
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Trees, Mycorrhiza and Minerals -Field Relevance of in vitro Experiments
- 2009
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Ingår i: Geomicrobiology Journal. - : Informa UK Limited. - 0149-0451 .- 1521-0529. ; 26, s. 389-401
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Tidskriftsartikel (refereegranskat)abstract
- Ectomycorrhizal fungi are mutualistic symbionts of boreal forest trees and may mediate mineral weathering through their direct access to photosyntentically derived carbon. In soil, fungal mycelia (i) provide a large surface for nutrient uptake; (ii) induce intense colonization of nutrient rich substrates; (iii) cause local acidification and (iv) produce organic acids. Mechanisms of ectomyorrhizal fungi induced weathering in response to nutrient limiting growth conditions remains largely unresolved. This review summarizes how current knowledge on fungal weathering is affected by experimental setup and conditions, i.e., pure or symbiotic growth, nitrogen source, the mean of detecting weathering activity and species examined.
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