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- 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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| 3. |
- Anderson, Craig, 1976, et al.
(författare)
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Influence of in situ biofilm coverage on the radionuclide adsorption capacity of subsurface granite
- 2007
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Ingår i: Environmental Science & Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 41:3, s. 830-836
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Tidskriftsartikel (refereegranskat)abstract
- Any migration of radionuclides from nuclear waste repositories is expected to be mitigated by adsorption to the host rocks surrounding hydraulically conductive fractures. Fluid rock interfaces are considered to be important barriers for nuclear waste disposal schemes but their adsorptive capacity can be affected by the growth of microbial biofilms. This study indicates that biofilms growing on fracture surfaces decrease the rocks adsorption capacity for migrating radionuclides except for trivalent species. Potential suppression of adsorption by biofilms should, therefore, be accounted for in performance safety assessment models. In this study, the adsorptive capacity of in situ anaerobic biofilms grown 450 m underground on either glass or granite slides was compared to the capacity of the same surfaces without biofilms. Surfaces were exposed to the radiotracers Co-60(II), Pm-147(III), Am-241(III), Th-234(IV), and Np-237(V) for a period of 660 h in a pH neutral anaerobic synthetic groundwater. Adsorption was investigated at multiple time points over the 660 h using liquid scintillation and ICP-MS. Results indicate that these surfaces adsorb between 0 and 85% of the added tracers under the conditions of the specific experiments. After 660 h, the distribution coefficients, R (ratio between what is sorbed and what is left in the aqueous phase), approached 3 x 10(4) m for Co-60, 3 x 10(5) m for Pm-147 and 24 'Am, I x 106 m for 234Th, and 1 x 103 m for 237Np. The highest rate of adsorption was during the first 200 h of the adsorption experiments and started to approach equilibrium after 500 h. Adsorption to colloids and precipitates contributed to decreases of up to 20% in the available Co-60, Pm-147, Am-241, and Np-237 in the adsorption systems. In the 234Th system 95% of the aqueous 234Th was removed by adsorbing to colloids. Although the range of R values for each surface tested generally overlapped, the biofilms consistently demonstrated lower R values except for the trivalant Pm-147 and Am-241 adsorption systems.
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| 4. |
- Johnsson, Anna, 1975, et al.
(författare)
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Bioligand-mediated partitioning of radionuclides to the aqueous phase
- 2008
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Ingår i: Journal of Radioanalytical and Nuclear Chemistry. - : Springer Science and Business Media LLC. - 0236-5731 .- 1588-2780. ; 277:3, s. 637-644
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Tidskriftsartikel (refereegranskat)abstract
- The aqueous-phase partitioning of 59Fe, 147Pm, 234Th and 241Am by complexing compounds from subsurface bacteria has previously been studied in the presence of quartz sand. In this study the aqueous-phase partitioning of pico- to submicromolar amounts of 59Fe, 147Pm, 234Th and 241Am was analyzed in the presence of TiO2 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. TiO2, with BET surface area of 49.9 m2·g-1, was added to the supernatant radionuclide mix, and the pH was adjusted to approximately 8. After incubation, the amount of radionuclide in the liquid phase of the samples and controls was analyzed using scintillation method. Two types of values were calculated: solution% = the activity maintained in solution relative to the total activity, and Q-values = the quotient between the activity in samples and the activity in controls. Aerobic supernatants had solution% values between 89% and 100% for 59Fe and between 18 and 43% for 234Th. The solution% values for 241Am and 147Pm were less than 2% overall, but the Q-values were between 34 and 115 times more 241Am in bacterial supernatants than in controls. The corresponding values for 147Pm ranged from 6 to 20 times more than in the control. The solution% values for all elements in the presence of anaerobic supernatants were below 2%, but the Q-values clustered around 7 for 59Fe and ranging from 2 to 29 for 234Th, indicated that anaerobic supernatants partitioned these elements to the aqueous phase. Both aerobic and anaerobic supernatants tested positive for complexing compounds when analyzed, using the Chrome Azurol S assay. Complexation with excreted organic ligands is most likely the reason for the higher amounts of metals in samples than in the controls. Hence, aerobically and anaerobically excreted organic ligands seem able to influence the mobility of radionuclides in aerobic and anaerobic environments contaminated with these compounds.
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| 5. |
- Clark, Andrew G., et al.
(författare)
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Evolution of genes and genomes on the Drosophila phylogeny
- 2007
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 450:7167, s. 203-218
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Tidskriftsartikel (refereegranskat)abstract
- Comparative analysis of multiple genomes in a phylogenetic framework dramatically improves the precision and sensitivity of evolutionary inference, producing more robust results than single-genome analyses can provide. The genomes of 12 Drosophila species, ten of which are presented here for the first time (sechellia, simulans, yakuba, erecta, ananassae, persimilis, willistoni, mojavensis, virilis and grimshawi), illustrate how rates and patterns of sequence divergence across taxa can illuminate evolutionary processes on a genomic scale. These genome sequences augment the formidable genetic tools that have made Drosophila melanogaster a pre-eminent model for animal genetics, and will further catalyse fundamental research on mechanisms of development, cell biology, genetics, disease, neurobiology, behaviour, physiology and evolution. Despite remarkable similarities among these Drosophila species, we identified many putatively non-neutral changes in protein-coding genes, non-coding RNA genes, and cis-regulatory regions. These may prove to underlie differences in the ecology and behaviour of these diverse species.
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| 6. |
- Gourdon, Pontus Emanuel, 1978, et al.
(författare)
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Optimized in vitro and in vivo expression of proteorhodopsin: A seven-transmembrane proton pump
- 2008
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Ingår i: Protein Expression and Purification. - : Elsevier BV. - 1096-0279 .- 1046-5928. ; 58:1, s. 103-113
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Tidskriftsartikel (refereegranskat)abstract
- Proteorhodopsin is an integral membrane light-harvesting proton pump that is found in bacteria distributed throughout global surface waters. Here, we present a protocol for functional in vitro production of pR using a commercial cell-free synthesis system yielding 1.0 mg purified protein per milliliter of cell lysate. We also present an optimized protocol for in vivo over-expression of pR in Escherichia coli, and a two-step purification yielding 5 mg of essentially pure functional protein per liter of culture. Both approaches are straightforward, rapid, and easily scalable. Thus either may facilitate the exploitation of pR for commercial biotechnological applications. Finally, the implications of some observations of the in vitro synthesis behavior, as well as preliminary results towards a structural determination of pR are discussed.
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