| 1. |
- Fuxelius, Hans-Henrik, et al.
(författare)
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The genomic and metabolic diversity of Rickettsia
- 2007
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Ingår i: Research in Microbiology. - : Elsevier BV. - 0923-2508 .- 1769-7123. ; 158:10, s. 745-753
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Tidskriftsartikel (refereegranskat)abstract
- Comparative genomics of Rickettsia and Orientia has revealed an exciting interplay between reductive evolutionary forces acting on metabolic genes in all species and proliferation of mobile genetic elements in some species. These contradictory evolutionary forces highlight the influence of chance, adaptation and host-cell exploitation during the evolution of intracellular bacteria.
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| 2. |
- Jonsson, Anders, et al.
(författare)
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Reduced activity of glutamine synthetase in Rhodospirillum rubrum mutants lacking the adenylyltransferase GlnE
- 2009
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Ingår i: Research in Microbiology. - : Elsevier BV. - 0923-2508 .- 1769-7123. ; 160:8, s. 581-4
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Tidskriftsartikel (refereegranskat)abstract
- In the nitrogen-fixing bacterium Rhodospirillum rubrum, the GlnE adenylyltransferase (encoded by glnE) catalyzes reversible adenylylation of glutamine synthetase, thereby regulating nitrogen assimilation. We have generated glnE mutant strains that are unable to adenylylate glutamine synthetase (GS). Surprisingly, the activity of GS was lower in the mutants than in the wild type, even when grown in nitrogen-fixing conditions. Our results support the proposal that R. rubrum can only cope with the absence of an adenylylation system in the presence of lowered GS expression or activity. In general terms, this report also provides further support for the central role of GS in bacterial metabolism.
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| 3. |
- Kupka, Daniel, et al.
(författare)
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Oxidation of elemental sulfur, tetrathionate and ferrous iron by the psychrotolerant Acidithiobacillus strain SS3.
- 2009
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Ingår i: Research in Microbiology. - : Elsevier BV. - 0923-2508 .- 1769-7123. ; 160:10, s. 767-774
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Tidskriftsartikel (refereegranskat)abstract
- Mesophilic iron and sulfur-oxidizing acidophiles are readily found in acid mine drainage sites and bioleaching operations, but relatively little is known about their activities at suboptimal temperatures and in cold environments. The purpose of this work was to characterize the oxidation of elemental sulfur (S(0)), tetrathionate (S4O6(2-)) and ferrous iron (Fe2+) by the psychrotolerant Acidithiobacillus strain SS3. The rates of elemental sulfur and tetrathionate oxidation had temperature optima of 20 degrees and 25 degrees C, respectively, determined using a temperature gradient incubator that involved narrow (1.1 degrees C) incremental increases from 5 degrees to 30 degrees C. Activation energies calculated from the Arrhenius plots were 61 and 89 kJ mol(-1) for tetrathionate and 110 kJ mol(-1) for S(0) oxidation. The oxidation of elemental sulfur produced sulfuric acid at 5 degrees C and decreased the pH to approximately 1. The low pH inhibited further oxidation of the substrate. In media with both S(0) and Fe2+, oxidation of elemental sulfur did not commence until all available ferrous iron was oxidized. These data on sequential oxidation of the two substrates are in keeping with upregulation and downregulation of several proteins previously noted in the literature. Ferric iron was reduced to Fe2+ in parallel with elemental sulfur oxidation, indicating the presence of a sulfur:ferric iron reductase system in this bacterium.
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| 4. |
- Otto, Karen
(författare)
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Biophysical approaches to study the dynamic process of bacterial adhesion.
- 2008
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Ingår i: Research in Microbiology. - : Elsevier BV. - 0923-2508 .- 1769-7123. ; 159:6, s. 415-22
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Tidskriftsartikel (refereegranskat)abstract
- Recent applications of biophysical techniques to the study of adhesion and biofilm formation are playing an important role in broadening our understanding of bacterial interactions. While non-invasive methods enable measurement of adhesion kinetics in real time, single-cell approaches provide information about adhesion forces mediated by specific cell surface structures. Promising approaches are presented in this review.
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| 5. |
- Poole, Anthony M
(författare)
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Horizontal gene transfer and the earliest stages of the evolution of life
- 2009
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Ingår i: Research in Microbiology. - : Elsevier. - 0923-2508 .- 1769-7123. ; 160:7, s. 473-480
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Tidskriftsartikel (refereegranskat)abstract
- Horizontal gene transfer (HGT) has been suggested to be the dominant hereditary process at the earliest stages of evolution. I examine this suggestion within the context of the problem of genetic parasites and suggest that extreme rates of transfer may in fact negatively impact evolutionary transitions. In regard to the proposal that HGT is Lamarckian, the apparent conflict between HGT and Darwinian evolution is easily avoided by considering HGT at the appropriate level of selection.
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| 6. |
- Steger, Kristin, et al.
(författare)
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Effects of differing temperature management on development of Actinobacteria populations during composting
- 2007
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Ingår i: Research in Microbiology. - : Elsevier BV. - 0923-2508 .- 1769-7123. ; 158:7, s. 617-624
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Tidskriftsartikel (refereegranskat)abstract
- Actinobacteria are believed to play a major role in organic matter degradation and humification processes in composts. In this study, the effects of different temperature regimes on the succession of Actinobacteria populations during composting were investigated in a laboratory reactor. Phospholipid fatty acid (PLFA) was used to investigate quantitative changes in the overall microbial biomass and community structure, and in the size of Actinobacteria populations. Qualitative changes were determined using PCR-DGGE (denaturing gradient gel electrophoresis) and sequencing of 16S rRNA genes with Actinobacteria-specific primers. The peak in total microbial biomass was roughly twice as high and delayed in trials where the maximum temperature was 40 °C, compared to those where it was 55 or 67 °C. There was a shift from members of Corynebacterium, Rhodococcus and Streptomyces at the onset to species of thermotolerant Actinobacteria in the cooling phase, e.g. Saccharomonospora viridis, Thermobifida fusca and Thermobispora bispora. In conclusion, temperature was an important selective factor for the development of Actinobacteria populations in composts, and they constituted a substantial part of the community in the later compost stages.
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