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- Bäckman, Ola, 1977
(författare)
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Character and Function of Anammox Bacteria under Environmental Stress
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- During the last few decades observations of novel processes involved in nitrogen transformations have fundamentally challenged the view of pathways and controlling mechanisms during local and global nitrogen cycling. Anaerobic ammonium oxidation (anammox) constitutes one of these new pathways where autotrophic bacteria oxidize ammonium by nitrite to dinitrogen gas under anaerobic conditions. Anammox provides a shunt during nitrogen transformations as it bypasses the classical pathway of aerobic nitrification coupled to anaerobic denitrification, a reaction scheme previously thought to be the sole source of dinitrogen gas in natural environments. Anammox is now acknowledged as a widespread and a globally important sink for nitrogen in water column and sediment systems. The first part of this thesis emphasises factors that regulate anammox bacteria in natural environments. Particular focus relates to coastal marine sediments and the importance of anammox for nitrogen removal under environmental stress associated with the temporal availability of oxygen and nutrients. Measurements of anammox and denitrification were made by 15N amendments including both shallow‐water illuminated autotrophic (net oxygen producing) sediments and deeper heterotrophic (net oxygen consuming) sediments. While rates of anammox were insignificant in illuminated sediments with primary production by benthic microalgae, anammox was found almost as important as denitrification for total N2 production in the dark heterotrophic sediments. Long term laboratory incubations under different oxygen conditions confirmed the importance of oxygen availability for the removal of bioavailable nitrogen by N2 production in surface sediments. In the second part of the thesis investigations focus on detailed mechanisms involved during anammox. Cutting edge analytical tools of membrane proteomics were utilized to identify and sub‐cellularly localize key proteins involved in the anammox reaction. Two proteins, the hydrazine synthase (previously hydrazine hydrolase) and an F‐ATPase, were identified by proteomics and LC‐MS/MS analysis and subsequently targeted for antibody production. Through immunogold electron microscopy the hydrazine synthase was assigned to the interior of the anammoxosome, the unique “organelle” of anammox bacteria. The F‐ATPase was associated with the anammoxosome membrane. These observations not only strengthen the important role of the anammoxosome during anammox metabolism, but also provide experimental support to the idea of the anammoxosome as an energized membrane.
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| 2. |
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| 3. |
- Karlsson, Roger, 1975, et al.
(författare)
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Identification of key proteins involved in the anammox reaction
- 2009
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Ingår i: FEMS microbiology letters. - : Oxford University Press (OUP). - 1574-6968 .- 0378-1097. ; 297:1, s. 87-94
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Tidskriftsartikel (refereegranskat)abstract
- Bacteria performing anaerobic ammonium oxidation (anammox) are key players in the global nitrogen cycle due to their inherent ability to convert biologically available nitrogen to N(2). Anammox is increasingly being exploited during wastewater treatment worldwide, and about 50% of the total N(2) production in marine environments is estimated to proceed by the anammox pathway. To fully understand the microbial functionality and mechanisms that control environmental feedbacks of the anammox reaction, key proteins involved in the reaction must be identified. In this study we have utilized an analytical protocol that facilitates detection of proteins associated with the anammoxosome, an intracellular membrane compartment within the anammox bacterium. The protocol enabled us to identify several key proteins of the anammox reaction including a hydrazine hydrolase producing hydrazine, a hydrazine-oxidizing enzyme converting hydrazine to N(2) and a membrane-bound ATP synthase generating ATP from the gradients of protons formed in the anammox reaction. We also performed immunogold labelling electron microscopy to determine the subcellular location of the hydrazine hydrolase. The results from our study support the hypothesis that proteins associated with the anammoxosome host the complete suite of reactions during anammox.
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| 4. |
- Karlsson, R., et al.
(författare)
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Subcellular localization of an ATPase in anammox bacteria using proteomics and immunogold electron microscopy
- 2014
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Ingår i: Fems Microbiology Letters. - : Oxford University Press (OUP). - 0378-1097. ; 354:1, s. 10-18
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Tidskriftsartikel (refereegranskat)abstract
- Anaerobic ammonium oxidation (anammox) has received significant attention during optimization of waste-water treatment and constitutes an important pathway for the removal of bioavailable nitrogen from natural environments. Studies of key catabolic enzymes indicate that the anammox reaction takes place inside the anammoxosome, an organelle-like membranous compartment of anammox bacteria. The anammoxosome has also been suggested as a site for ATP synthesis. A lipid-based protein immobilization technique, previously used to identify proteins essential for the anammox reaction, was in this study used to select linear epitopes for antibodies specifically targeted against an identified ATPase. The approach of using proteomics and bioinformatics as tools for selecting antibody targets for immunolocalization provides an important alternative to traditional methods for selection of specific antibodies. Immunogold electron microscopy and statistical evaluations indicated that the antibodies against the ATPase were exclusively found associated with the anammoxosome membrane. This provides strong evidence for ATP synthesis by an intracellular proton motive force in anammox bacteria. Within prokaryotes, an ATP synthase associated with an intracellular compartment is a feature unique for anammox bacteria.
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| 5. |
- Wittorf, Lea, et al.
(författare)
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Habitat partitioning of marine benthic denitrifier communities in response to oxygen availability
- 2016
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Ingår i: Environmental Microbiology Reports. - : Wiley. - 1758-2229. ; 8:4, s. 486-492
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Tidskriftsartikel (refereegranskat)abstract
- Denitrification is of global significance for the marine nitrogen budget and the main process for nitrogen loss in coastal sediments. This facultative anaerobic respiratory pathway is modular in nature and the final step, the reduction of nitrous oxide (N2O), is performed by microorganisms with a complete denitrification pathway as well as those only capable of N2O reduction. Fluctuating oxygen availability is a significant driver of denitrification in sediments, but the effects on the overall N2O-reducing community that ultimately controls the emission of N2O from marine sediments is not well known. To investigate the effects of different oxygen regimes on N2O reducing communities, coastal marine surface sediment was incubated in microcosms under oxic, anoxic or oscillating oxygen conditions in the overlying water for 137 days. Quantification of the genetic potential for denitrification, anammox and respiratory ammonification indicated that denitrification supported nitrogen removal in these sediments. Furthermore, denitrifiers with a complete pathway were identified as the dominant community involved in N2O reduction, rather than organisms that are only N2O reducers. Specific lineages within each group were associated with different oxygen regimes suggesting that oxygen availability in the overlying water is associated with habitat partitioning of N2O reducers in coastal marine surface sediments.
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