| 1. |
- Bugaytsova, Zhanna, et al.
(författare)
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Localization, purification and properties of a tetrathionate hydrolase from Acidithiobacillus caldus
- 2004
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Ingår i: European Journal of Biochemistry. - Hoboken : Wiley-Blackwell. - 0014-2956 .- 1432-1033. ; 271:2, s. 272-280
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Tidskriftsartikel (refereegranskat)abstract
- The moderately thermophilic bacterium Acidithiobacillus caldus is found in bacterial populations in many bioleaching operations throughout the world. This bacterium oxidizes elemental sulfur and other reduced inorganic sulfur compounds as the sole source of energy. The purpose of this study was to purify and characterize the tetrathionate hydrolase of A. caldus. The enzyme was purified 16.7-fold by one step chromatography using a SP Sepharose column. The purified enzyme resolved into a single band in 10% polyacrylamide gel, both under denaturing and native conditions. Its homogeneity was confirmed by N-terminal amino acid sequencing. Tetrathionate hydrolase was shown to be a homodimer with a molecular mass of 103 kDa (composed from two 52 kDa monomers). The purified enzyme had optimum activity at pH 3.0 and 40 degreesC and an isoelectric point of 9.8. The periplasmic localization of the enzyme was determined by differential fractionation of A. caldus cells. Detected products of the tetrathionate hydrolase reaction were thiosulfate and pentathionate as confirmed by RP-HPLC analysis. The activity of the purified enzyme was drastically enhanced by divalent metal ions.
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| 2. |
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| 3. |
- Dopson, Mark, et al.
(författare)
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ATP generation during reduced inorganic sulfur compound oxidation by Acidithiobacillus caldus is exclusively due to electron transport phosphorylation.
- 2002
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Ingår i: Extremophiles. - : Springer Science and Business Media LLC. - 1431-0651 .- 1433-4909. ; 6:2, s. 123-129
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Tidskriftsartikel (refereegranskat)abstract
- The synthesis of adenosine 5-triphosphate (ATP) (increase in phosphorylation potential) during the oxidation of reduced inorganic sulfur compounds was studied in the moderately thermophilic acidophileAcidithiobacillus caldus (strain KU) (formerly Thiohacillus caldus). The phosphorylation potential increased during the oxidation of all reduced inorganic sulfur compounds tested compared with resting cells. The generation of ATP in whole cells was inhibited by the F0F1 ATPase inhibitor oligomycin, electron transport chain inhibitors, valinomycin and potassium ions. There was no increase in the phosphorylation potential, nor synthesis of ATP. in the absence of electron transport. An apparent lack of substrate-level phosphorylation was indicated by the lack of adenosine 5-phosphosulfate reductase in tetrathionate-grown At. caldus. Studies were also performed on the synthesis of ATP by membrane vesicles of At. caldus when presented with an artificial proton gradient. Complete inhibition of ATP synthesis in these vesicles occurred when they were loaded with N,N-dicyclohexylcarbodiimide (DCCD), but not when they were loaded with oligomycin, vanadate or electron transport chain inhibitors. The data presented here suggest that during the oxidation of reduced inorganic sulfur compounds by At. caldus, all ATP is synthesized by oxidative phosphorylation via a membrane-bound F0F1 ATPase driven by a proton gradient.
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| 4. |
- Dopson, Mark, et al.
(författare)
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Toxicity of metal extraction and flotation chemicals to Sulfolobus metallicus and chalcopyrite bioleaching
- 2006
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Ingår i: Hydrometallurgy. - : Elsevier BV. - 0304-386X .- 1879-1158. ; 81:3-4, s. 205-213
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Tidskriftsartikel (refereegranskat)abstract
- The effect of chemicals used in preparation of mineral concentrates and subsequent extraction of metals to the thermophilic, acidophilic microorganism Sulfolobus metallicus has been tested. The chemicals tested included collectors and frothers employed during flotation of the oreto produce a mineral concentrate, solvent extraction reagents used to remove metals after leaching, and thiocyanate produced as a decomposition product during cyanidation for gold recovery. The effect of these chemicals to S. metallicus depends on the conditions and time frame that the experiments were carried out due to their mode of toxicity and stability in acid pH. The metal extraction chemical that had the least effect on bioleaching was potassium amyl xanthate that increased the leaching rate, possibly due to solubilization of sulfur that can form passivation layers on the surface of minerals. The frother Flotanol C-7 decreased the chalcopyrite leaching rate, despite having no effect on Fe2+ oxidation by S. metallicus resting cells. This is probably due to inhibition of oxygen transfer during bioleaching that had little effect on Fe2+ oxidation over 20 min. Solvent extraction chemicals inhibited both Fe2+ oxidation and bioleaching suggesting their mode of inhibition is due toFe2+ oxidation. The results suggest that relevant concentrations of metal extraction and flotation chemicals can be toxic to chalcopyritebioleaching by S. metallicus.
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| 5. |
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| 6. |
- Hallberg, K. B., et al.
(författare)
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Arsenic toxicity is not due to a direct effect on the oxidation of reduced inorganic sulfur compounds byThiobacillus caldus
- 1996
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Ingår i: FEMS Microbiology Letters. - 0378-1097 .- 1574-6968. ; 145:3, s. 409-414
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Tidskriftsartikel (refereegranskat)abstract
- Thiobacillus caldus is a moderately thermophilic acidophile which has been implicated in the biooxidation of arsenic containing mineral sulfides. The toxic effects of arsenic on this bacterium are presented here. Addition of arsenite to a growing culture of T. caldus caused a transient increase in the optical density of the culture while causing a simultaneous decrease in cell viability. The increase in optical density was shown to be due to the formation of extracellular sulfur. The oxidation rates of tetrathionate and thiosulfate were decreased by increasing concentrations of arsenite, while in a culture induced to arsenic resistance the rates were not as adversely effected. Sulfur oxidation was also inhibited to the same extent as tetrathionate oxidation, with the oxidation of solid sulfur being slightly more effected than the oxidation of sulfur dissolved in acetone. Thus, bactericidal arsenite causes a transient formation of extracellular sulfur in the culture supernatant of T. caldus yet the toxicity of arsenite is not due to direct inhibitory effects on reduced inorganic sulfur compound oxidation by these bacteria.
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| 7. |
- Hallberg, K B, et al.
(författare)
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Reduced sulfur compound oxidation by Thiobacillus caldus.
- 1996
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Ingår i: Journal of Bacteriology. - 0021-9193 .- 1098-5530. ; 178:1, s. 6-11
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Tidskriftsartikel (refereegranskat)abstract
- The oxidation of reduced inorganic sulfur compounds was studied by using resting cells of the moderate thermophile Thiobacillus caldus strain KU. The oxygen consumption rate and total oxygen consumed were determined for the reduced sulfur compounds thiosulfate, tetrathionate, sulfur, sulfide, and sulfite in the absence and in the presence of inhibitors and uncouplers. The uncouplers 2,4-dinitrophenol and carbonyl cyanide m-chlorophenyl-hydrazone had no affect on the oxidation of thiosulfate, suggesting that thiosulfate is metabolized periplasmically. In contrast, the uncouplers completely inhibited the oxidation of tetrathionate, sulfide, sulfur, and sulfite, indicating that these compounds are metabolized in the cytoplasm of T. caldus KU. N-Ethylmaleimide inhibited the oxidation of tetrathionate and thiosulfate at the stage of elemental sulfur, while 2-heptyl-4-hydroxyquinoline-N-oxide stopped the oxidation of thiosulfate, tetrathionate, and elemental sulfur at the stage of sulfite. The following intermediates in the oxidation of the sulfur compounds were found by using uncouplers and inhibitors: thiosulfate was oxidized to tetrathionate, elemental sulfur was formed during the oxidation of tetrathionate and sulfide, and sulfite was found as an intermediate of tetrathionate and sulfur metabolism. On the basis of these data we propose a model for the metabolism of the reduced inorganic sulfur compounds by T. caldus KU.
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| 8. |
- 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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| 9. |
- Lindström, E. Börje, et al.
(författare)
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A sequential two-step process using moderately and extremely thermophilic cultures for biooxidation of refractory gold concentrates
- 2003
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Ingår i: Hydrometallurgy. - 0304-386X .- 1879-1158. ; 71:1-2, s. 21-30
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Tidskriftsartikel (refereegranskat)abstract
- In many cases, the use of extreme thermophiles, like the archeon Sulfolobus metallicus, in a continuous bioleaching process of gold concentrates is limited by the arsenic content in the feed. In this work, a sequential two-step bioleaching process for gold-containing refractory pyrite/arsenopyrite concentrates has been investigated for the possibility of lowering the toxicity of arsenic with respect to the extremely thermophilic culture. In the first stage, a moderately thermophilic culture was used followed by the extremely thermophilic S. metallicus in the second stage. It was found that the S. metallicus culture survives higher arsenic concentrations than expected when the concentrate was pre-oxidized at a lower temperature. Thus, with this sequential two-step bioleaching process, it is possible to reduce the toxicity of the released arsenic. Therefore, the use of higher pulp densities of arsenic-containing minerals is enabled. When the leached mineral residues were subjected to cyanidation, cyanide consumption and thiocyanate formation were significantly lower after the second stage. In addition, a somewhat higher gold and silver grade was found in the residue from the concentrate ultimately oxidized by S. metallicus.
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| 10. |
- Lindström, E. Börje, et al.
(författare)
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Thermophilic bioleaching of arsenopyrite using Sulfolobus and a semi-continuous laboratory procedure
- 1990
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Ingår i: Journal of Industrial Microbiology & Biotechnology. - 1367-5435 .- 1476-5535. ; 5:6, s. 375-382
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Tidskriftsartikel (refereegranskat)abstract
- A laboratory equipment for pumping slurries is described. The pumping is performed semi-continuously by using a plastic syringe, a set of different valves, and a programmable electronic unit. The reproducibility of the pumping is demonstrated. Bioleaching of a gold-containing arsenopyrite slurry was done withSulfolobus at 70°C using the semi-continuous procedure and with a retention time of 100 h for the mineral. Arsenic was completely released at a rate of 109 mg l-1 h-1. The gold recovery is related to the amount of iron and arsenic dissolved and is shown to have a correlation factor of approximately one relative to the release of arsenic.
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