| 1. |
- Baker-Austin, Craig, et al.
(författare)
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Extreme arsenic resistance by the acidophilic archaeon 'Ferroplasma acidarmanus' Fer1.
- 2007
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Ingår i: Extremophiles. - : Springer Science and Business Media LLC. - 1431-0651 .- 1433-4909. ; 11:3, s. 425-34
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Tidskriftsartikel (refereegranskat)abstract
- 'Ferroplasma acidarmanus' Fer1 is an arsenic-hypertolerant acidophilic archaeon isolated from the Iron Mountain mine, California; a site characterized by heavy metals contamination. The presence of up to 10 g arsenate per litre [As(V); 133 mM] did not significantly reduce growth yields, whereas between 5 and 10 g arsenite per litre [As(III); 67-133 mM] significantly reduced the yield. Previous bioinformatic analysis indicates that 'F. acidarmanus' Fer1 has only two predicted genes involved in arsenic resistance and lacks a recognizable gene for an arsenate reductase. Biochemical analysis suggests that 'F. acidarmanus' Fer1 does not reduce arsenate indicating that 'F. acidarmanus' Fer1 has an alternative resistance mechanism to arsenate other than reduction to arsenite and efflux. Primer extension analysis of the putative ars transcriptional regulator (arsR) and efflux pump (arsB) demonstrated that these genes are co-transcribed, and expressed in response to arsenite, but not arsenate. Two-dimensional polyacrylamide gel electrophoresis analysis of 'F. acidarmanus' Fer1 cells exposed to arsenite revealed enhanced expression of proteins associated with protein refolding, including the thermosome Group II HSP60 family chaperonin and HSP70 DnaK type heat shock proteins. This report represents the first molecular and proteomic study of arsenic resistance in an acidophilic archaeon.
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| 2. |
- Cava, Felipe, et al.
(författare)
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Thermus thermophilus as biological model
- 2009
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Ingår i: Extremophiles. - : Springer Science and Business Media LLC. - 1431-0651 .- 1433-4909. ; 13:2, s. 213-31
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Tidskriftsartikel (refereegranskat)abstract
- Thermus spp is one of the most wide spread genuses of thermophilic bacteria, with isolates found in natural as well as in man-made thermal environments. The high growth rates, cell yields of the cultures, and the constitutive expression of an impressively efficient natural competence apparatus, amongst other properties, make some strains of the genus excellent laboratory models to study the molecular basis of thermophilia. These properties, together with the fact that enzymes and protein complexes from extremophiles are easier to crystallize have led to the development of an ongoing structural biology program dedicated to T. thermophilus HB8, making this organism probably the best so far known from a protein structure point view. Furthermore, the availability of plasmids and up to four thermostable antibiotic selection markers allows its use in physiological studies as a model for ancient bacteria. Regarding biotechnological applications this genus continues to be a source of thermophilic enzymes of great biotechnological interest and, more recently, a tool for the over-expression of thermophilic enzymes or for the selection of thermostable mutants from mesophilic proteins by directed evolution. In this article, we review the properties of this organism as biological model and its biotechnological applications.
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| 3. |
- Dopson, Mark, et al.
(författare)
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Towards determining details of anaerobic growth coupled to ferric iron reduction by the acidophilic archaeon 'Ferroplasma acidarmanus' Fer1.
- 2007
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Ingår i: Extremophiles. - : Springer Science and Business Media LLC. - 1431-0651 .- 1433-4909. ; 11:1, s. 159-68
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Tidskriftsartikel (refereegranskat)abstract
- Elucidation of the different growth states of Ferroplasma species is crucial in understanding the cycling of iron in acid leaching sites. Therefore, a proteomic and biochemical study of anaerobic growth in 'Ferroplasma acidarmanus' Fer1 has been carried out. Anaerobic growth in Ferroplasma spp. occurred by coupling oxidation of organic carbon with the reduction of Fe(3+); but sulfate, nitrate, sulfite, thiosulfate, and arsenate were not utilized as electron acceptors. Rates of Fe(3+) reduction were similar to other acidophilic chemoorganotrophs. Analysis of the 'F. acidarmanus' Fer1 proteome by 2-dimensional polyacrylamide gel electrophoresis revealed ten key proteins linked with central metabolic pathways > or =4 fold up-regulated during anaerobic growth. These included proteins putatively identified as associated with the reductive tricarboxylic acid pathway used for anaerobic energy production, and others including a putative flavoprotein involved in electron transport. Inhibition of anaerobic growth and Fe(3+) reduction by inhibitors suggests the involvement of electron transport in Fe(3+)reduction. This study has increased the knowledge of anaerobic growth in this biotechnologically and environmentally important acidophilic archaeon.
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| 4. |
- Ettema, Thijs J. G., et al.
(författare)
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The non-phosphorylating glyceraldehyde-3-phosphate dehydrogenase (GAPN) of Sulfolobus solfataricus : a key-enzyme of the semi-phosphorylative branch of the Entner-Doudoroff pathway
- 2008
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Ingår i: Extremophiles. - : Springer Science and Business Media LLC. - 1431-0651 .- 1433-4909. ; 12:1, s. 75-88
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Tidskriftsartikel (refereegranskat)abstract
- Archaea utilize a branched modification of the classical Entner-Doudoroff (ED) pathway for sugar degradation. The semi-phosphorylative branch merges at the level of glyceraldehyde 3-phosphate (GAP) with the lower common shunt of the Emden-Meyerhof-Parnas pathway. In Sulfolobus solfataricus two different GAP converting enzymes-classical phosphorylating GAP dehydrogenase (GAPDH) and the non-phosphorylating GAPDH (GAPN)-were identified. In Sulfolobales the GAPN encoding gene is found adjacent to the ED gene cluster suggesting a function in the regulation of the semi-phosphorylative ED branch. The biochemical characterization of the recombinant GAPN of S. solfataricus revealed that-like the well-characterized GAPN from Thermoproteus tenax-the enzyme of S. solfataricus exhibits allosteric properties. However, both enzymes show some unexpected differences in co-substrate specificity as well as regulatory fine-tuning, which seem to reflect an adaptation to the different lifestyles of both organisms. Phylogenetic analyses and database searches in Archaea indicated a preferred distribution of GAPN (and/or GAP oxidoreductase) in hyperthermophilic Archaea supporting the previously suggested role of GAPN in metabolic thermoadaptation. This work suggests an important role of GAPN in the regulation of carbon degradation via modifications of the EMP and the branched ED pathway in hyperthermophilic Archaea.
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| 5. |
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| 6. |
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| 7. |
- Mamo, Gashaw, et al.
(författare)
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Fusion of carbohydrate binding modules from Thermotoga neapolitana with a family 10 xylanase from Bacillus halodurans S7
- 2007
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Ingår i: Extremophiles. - : Springer Science and Business Media LLC. - 1433-4909 .- 1431-0651. ; 11:1, s. 169-177
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Tidskriftsartikel (refereegranskat)abstract
- Xylanase A of Thermotoga neapolitana contains binding domains both at the N- and C-terminal ends of the catalytic domain. In the N-terminal position it contains two carbohydrate-binding modules (CBM) which belong to family 22. These CBMs bind xylan but not to cellulose. The gene encoding the mature peptide of these CBMs was fused with an alkaline active GH10 xylanase from Bacillus halodurans S7 and expressed in Escherichia coli. The (His)(6) tagged hybrid protein was purified by immobilized metal affinity chromatography and characterized. Xylan binding by the chimeric protein was influenced by NaCl concentration and pH of the binding medium. Binding increased with increasing salt concentration up to 200 mM. Higher extent of binding was observed under acidic conditions. The fusion of the CBM structures enhanced the hydrolytic efficiency of the xylanase against insoluble xylan, but decreased the stability of the enzyme. The optimum temperature and pH for the activity of the xylanase did not change.
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| 8. |
- Srimathi, Soundararajan, et al.
(författare)
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Intrinsic halotolerance of the psychrophilic alpha-amylase from Pseudoalteromonas haloplanktis
- 2007
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Ingår i: Extremophiles. - : Springer Science and Business Media LLC. - 1433-4909 .- 1431-0651. ; 11:3, s. 505-515
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Tidskriftsartikel (refereegranskat)abstract
- The halotolerance of a cold adapted alpha-amylase from the psychrophilic bacterium Pseudoalteromonas haloplanktis (AHA) was investigated. AHA exhibited hydrolytic activity over a broad range of NaCl concentrations (0.01-4.5 M). AHA showed 28% increased activity in 0.5-2.0 M NaCl compared to that in 0.01 M NaCl. In contrast, the corresponding mesophilic (Bacillus amyloliquefaciens) and thermostable (B. licheniformis) alpha-amylases showed a 39 and 46% decrease in activity respectively. Even at 4.5 M NaCl, 80% of the initial activity was detected for AHA, whereas the mesophilic and thermostable enzymes were inactive. Besides an unaltered fluorescence emission and secondary structure, a 10 degrees C positive shift in the temperature optimum, a stabilization factor of > 5 for thermal inactivation and a Delta T-m of 8.3 degrees C for the secondary structure melting were estimated in 2.7 M NaCl. The higher activation energy, half-life time and T-m indicated reduced conformational dynamics and increased rigidity in the presence of higher NaCl concentrations. A comparison with the sequences of other halophilic alpha-amylases revealed that AHA also contains higher proportion of small hydrophobic residues and acidic residues resulting in a higher negative surface potential. Thus, with some compromise in cold activity, psychrophilic adaptation has also manifested halotolerance to AHA that is comparable to the halophilic enzymes.
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| 9. |
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| 10. |
- Säwström, Christin, et al.
(författare)
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Bacteriophage in polar inland waters.
- 2008
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Ingår i: Extremophiles. - : Springer Science and Business Media LLC. - 1431-0651 .- 1433-4909. ; 12:2, s. 167-175
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Tidskriftsartikel (refereegranskat)abstract
- Bacteriophages are found wherever microbial life is present and play a significant role in aquatic ecosystems. They mediate microbial abundance, production, respiration, diversity, genetic transfer, nutrient cycling and particle size distribution. Most studies of bacteriophage ecology have been undertaken at temperate latitudes. Data on bacteriophages in polar inland waters are scant but the indications are that they play an active and dynamic role in these microbially dominated polar ecosystems. This review summarises what is presently known about polar inland bacteriophages, ranging from subglacial Antarctic lakes to glacial ecosystems in the Arctic. The review examines interactions between bacteriophages and their hosts and the abiotic and biotic variables that influence these interactions in polar inland waters. In addition, we consider the proportion of the bacteria in Arctic and Antarctic lake and glacial waters that are lysogenic and visibly infected with viruses. We assess the relevance of bacteriophages in the microbial loop in the extreme environments of Antarctic and Arctic inland waters with an emphasis on carbon cycling.
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| 11. |
- Åhrman, Emma, et al.
(författare)
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Small heat shock proteins prevent aggregation of citrate synthase and bind to the N-terminal region which is absent in thermostable forms of citrate synthase
- 2007
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Ingår i: Extremophiles. - : Springer Science and Business Media LLC. - 1433-4909 .- 1431-0651. ; 11:5, s. 659-666
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Tidskriftsartikel (refereegranskat)abstract
- Citrate synthase (CS) is often used in chaperone assays since this thermosensitive enzyme aggregates at moderately increased temperatures. Small heat shock proteins (sHsps) are molecular chaperones specialized in preventing the aggregation of other proteins, termed substrate proteins, under conditions of transient heat stress. To investigate the mechanism whereby sHsps bind to and stabilize a substrate protein, we here used peptide array screening covering the sequence of porcine CS (P00889). Strong binding of sHsps was detected to a peptide corresponding to the most N-terminal alpha-helix in CS (amino acids Leu(13) to Gln(27)). The N-terminal alpha-helices in the CS dimer intertwine with the C-terminus in the other subunit and together form a stem-like structure which is protruding from the CS dimer. This stem-like structure is absent in thermostable forms of CS from thermophilic archaebacteria like Pyrococcus furiosus and Sulfolobus solfatacarium. These data therefore suggest that thermostabilization of thermosensitive CS by sHsps is achieved by stabilization of the C- and N-terminae in the protruding thermosensitive softspot, which is absent in thermostable forms of the CS dimer.
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