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1.
Anaerobic ammonium oxidation (anammox) is both a promising process in wastewater treatment and a long overlooked microbial physiology that can contribute significantly to biological nitrogen cycling in the world's oceans. Anammox is mediated by a monophyletic group of bacteria that branches deeply in the Planctomycetales. Here we describe a new genus and species of anaerobic ammonium oxidizing planctomycetes, discovered in a wastewater treatment plant (wwtp) treating landfill leachate in Pitsea, UK. The biomass from this wwtp showed high anammox activity (5.0 +/- 0.5 nmol/mg protein/min) and produced hydrazine from hydroxylamine, one of the unique features of anammox bacteria. Eight new planctomycete 16S rRNA gene sequences were present in the 16S rRNA gene clone library generated from the biomass. Four of these were affiliated to known anammox 16S rRNA gene sequences, but branched much closer to the root of the planctomycete line of descent. Fluorescence in situ hybridization (FISH) with oligonucleotide probes specific for these new sequences showed that two species (belonging to the same genus) together made up > 99% of the planctomycete population which constituted 20% of the total microbial community. The identification of these organisms as typical anammox bacteria was confirmed with electron microscopy and lipid analysis. The new species, provisionally named Candidatus "Scalindua brodae" and "Scalindua wagneri" considerably extend the biodiversity of the anammox lineage on the 16S rRNA gene level, but otherwise resemble known anammox bacteria. Simultaneously, another new species of the same genus, Candidatus "Scalindua sorokinii", was detected in the water column of the Black Sea, making this genus the most widespread of all anammox bacteria described so far.  相似文献   
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Recently, two fresh water species, "Candidatus Brocadia anammoxidans" and "Candidatus Kuenenia stuttgartiensis", and one marine species, "Candidatus Scalindua sorokinii", of planctomycete anammox bacteria have been identified. "Candidatus Scalindua sorokinii" was discovered in the Black Sea, and contributed substantially to the loss of fixed nitrogen. All three species contain a unique organelle—the anammoxosome—in their cytoplasm. The anammoxosome contains the hydrazine/hydroxylamine oxidoreductase enzyme, and is thus the site of anammox catabolism. The anammoxosome is surrounded by a very dense membrane composed almost exclusively of linearly concatenated cyclobutane-containing lipids. These so-called 'ladderanes' are connected to the glycerol moiety via both ester and ether bonds. In natural and man-made ecosystems, anammox bacteria can cooperate with aerobic ammonium-oxidising bacteria, which protect them from harmful oxygen, and provide the necessary nitrite. The cooperation of these two groups of ammonium-oxidising bacteria is the microbial basis for a sustainable one reactor system, CANON (completely autotrophic nitrogen-removal over nitrite) to remove ammonia from high strength wastewater.  相似文献   
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Anaerobic ammonium oxidation (anammox) is a recently discovered microbial pathway and a cost-effective way to remove ammonium from wastewater. Anammox bacteria have been described as obligate chemolithoautotrophs. However, many chemolithoautotrophs (i.e., nitrifiers) can use organic compounds as a supplementary carbon source. In this study, the effect of organic compounds on anammox bacteria was investigated. It was shown that alcohols inhibited anammox bacteria, while organic acids were converted by them. Methanol was the most potent inhibitor, leading to complete and irreversible loss of activity at concentrations as low as 0.5 mM. Of the organic acids acetate and propionate, propionate was consumed at a higher rate (0.8 nmol min(-1) mg of protein(-1)) by Percoll-purified anammox cells. Glucose, formate, and alanine had no effect on the anammox process. It was shown that propionate was oxidized mainly to CO(2), with nitrate and/or nitrite as the electron acceptor. The anammox bacteria carried out propionate oxidation simultaneously with anaerobic ammonium oxidation. In an anammox enrichment culture fed with propionate for 150 days, the relative amounts of anammox cells and denitrifiers did not change significantly over time, indicating that anammox bacteria could compete successfully with heterotrophic denitrifiers for propionate. In conclusion, this study shows that anammox bacteria have a more versatile metabolism than previously assumed.  相似文献   
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The demand for new and sustainable systems for nitrogen removal has increased dramatically in the last decade. It is clear that the conventional systems cannot deal with the increasing nitrogen loads in a cost effective way. As an alternative, the implementation of the anammox (anaerobic ammonium oxidation) process in the treatment of wastewater with high ammonium concentrations has been started. The compact anammox reactors can sustain high nitrogen loads without any problems. The highest observed anammox capacity is 8.9 kg N removed m-3 reactor day-1. The first 75 m3 anammox reactor is operating in Rotterdam, the Netherlands, combined with the partial nitrification process Single reaction system for High Ammonium Removal Over Nitrite (SHARON). Partial nitrification and anammox can also be combined in one reactor systems like Completely Autotrophic Nitrogen removal Over Nitrite (CANON) or Oxygen Limited Ammonium removal via Nitrification Denitrification (OLAND) where aerobic ammonium-oxidizing bacteria (AOB) and anammox bacteria cooperate under oxygen-limitation. These systems remove about 1.5 kg N m-3 reactor day-1. In addition to ammonium, urea can also be converted in the CANON system after a two-week adaptation period. The ecophysiological properties of the anammox bacteria make them very well suited to convert ammonium and nitrite. The Ks values for ammonium and nitrite are below 5 M. However, nitrite above 10 mM is detrimental for the anammox process, and oxygen reversibly inhibits the process at concentrations as low as 1 M. Acetate and propionate can be used by the anammox bacteria to convert nitrite and nitrate, whereas methanol and ethanol severely inhibit the anammox reaction. The enzyme hydroxylamine/hydrazine oxidoreductase (HAO), one of the key enzymes, is located in the anammoxosome, which is a membrane bound organelle. The membranes of the anammox bacteria contain unique ladderane lipids and hopanoids. The bacteria responsible for the anammox reaction are related to the Planctomycetes. The first anammox bacteria were isolated via Percoll centrifugation and characterized as Candidatus Brocadia anammoxidans. Survey of different wastewater treatment plants using anammox specific 16S rRNA gene primers and anammox specific oligonucleotide probes has revealed the presence of at least three other anammox bacteria, which have been tentatively named Candidatus Kuenenia stuttgartiensis, Candidatus Scalindua wagneri and Candidatus Scalindua brodae. A close relative of the latter, Candidatus Scalindua sorokinii was found to be responsible for about 50% of the nitrogen conversion in the anoxic zone of the Black Sea, making the anammox bacteria an important player in the oceanic nitrogen cycle.  相似文献   
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Anaerobic ammonium oxidation (anammox) is a recently discovered microbial pathway and a cost-effective way to remove ammonium from wastewater. Anammox bacteria have been described as obligate chemolithoautotrophs. However, many chemolithoautotrophs (i.e., nitrifiers) can use organic compounds as a supplementary carbon source. In this study, the effect of organic compounds on anammox bacteria was investigated. It was shown that alcohols inhibited anammox bacteria, while organic acids were converted by them. Methanol was the most potent inhibitor, leading to complete and irreversible loss of activity at concentrations as low as 0.5 mM. Of the organic acids acetate and propionate, propionate was consumed at a higher rate (0.8 nmol min−1 mg of protein−1) by Percoll-purified anammox cells. Glucose, formate, and alanine had no effect on the anammox process. It was shown that propionate was oxidized mainly to CO2, with nitrate and/or nitrite as the electron acceptor. The anammox bacteria carried out propionate oxidation simultaneously with anaerobic ammonium oxidation. In an anammox enrichment culture fed with propionate for 150 days, the relative amounts of anammox cells and denitrifiers did not change significantly over time, indicating that anammox bacteria could compete successfully with heterotrophic denitrifiers for propionate. In conclusion, this study shows that anammox bacteria have a more versatile metabolism than previously assumed.  相似文献   
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Anaerobic methane oxidation coupled to denitrification was recently assigned to bacteria belonging to the uncultured phylum NC10. In this study, we incubated sediment from a eutrophic ditch harboring a diverse community of NC10 bacteria in a bioreactor with a constant supply of methane and nitrite. After 6 months, fluorescence in situ hybridization showed that NC10 bacteria dominated the resulting population. The enrichment culture oxidized methane and reduced nitrite to dinitrogen gas. We assessed NC10 phylum diversity in the inoculum and the enrichment culture, compiled the sequences currently available for this bacterial phylum, and showed that of the initial diversity, only members of one subgroup had been enriched. The growth of this subgroup was monitored by quantitative PCR and correlated to nitrite-reducing activity and the total biomass of the culture. Together, the results indicate that the enriched subgroup of NC10 bacteria is responsible for anaerobic methane oxidation coupled to nitrite reduction. Due to methodological limitations (a strong bias against NC10 bacteria in 16S rRNA gene clone libraries and inhibition by commonly used stopper material) the environmental distribution and importance of these bacteria could be largely underestimated at present.Atmospheric concentrations of methane have risen 2.6-fold since preindustrial times (10). After several years of stagnation, there was again a clear increase in the methane concentration in 2007 (29). Currently, it is uncertain whether an increase in the number of sources and production or a decrease in the number of sinks and consumption is responsible for this reversal of the trend.Freshwater habitats like natural wetlands and rice fields are a major source (38% [9]) of atmospheric methane. In the absence of other documented electron donors, aerobic methane oxidation is assumed to be the most important sink in these habitats, but the role of alternative electron donors is not well understood (19, 30). Anaerobic methane oxidation coupled to denitrification is energetically favorable, but evidence that it occurs is scarce. In marine, methane-containing sediments, nitrate and nitrite are usually not quantitatively important electron acceptors; in freshwater sediments the denitrifying and aerobic zones are in close proximity (3, 22, 35), possibly masking the process from detection. To our knowledge, concomitant methane and nitrate profiles of sediments have never been published.So far, methane oxidation coupled to denitrification has received the most attention in the field of hydrogeology. In groundwater, contamination with nitrate and nitrite occurs frequently, whereas electron donors are limiting. Methane plumes often form around landfills, and their attenuation has sometimes been attributed to denitrification (2, 37). So far, a single previous study unambiguously demonstrated anaerobic oxidation of methane coupled to denitrification in a contaminated freshwater aquifer (32). The first in vitro observation of anaerobic methane oxidation coupled to denitrification came from a laboratory-scale sludge digestor (11). The use of a laboratory enrichment culture also eventually resulted in identification of the organisms involved; bacteria of the NC10 phylum and archaea of the order Methanosarcinales dominated a mixed culture carrying out anaerobic methane oxidation coupled to denitrification (27). This culture was enriched from a freshwater canal sediment after 1 year of continuous supply of methane and nitrite. Subsequently, the archaea were shown to be dispensable, as they disappeared after prolonged incubation of the same culture (7). Mass balance calculations showed that methane oxidation was coupled to the reduction of nitrite with a 3:8 stoichiometry, in accordance with theoretical expectations. The bacteria that dominated the mixed culture and apparently oxidized methane anaerobically are members of the NC10 phylum, one of the many phyla having no members in pure culture (8, 28). The 16S rRNA gene sequences of such organisms, however, have been found in a number of environmental surveys of aquatic environments; e.g., the most closely related sequences have been found in aquifers (1, 23) and lake sediments (13, 17). Sequence similarity and phylogenetic affiliation may indicate similar metabolic capacities of organisms, but by itself this is not sufficient to infer similar metabolism (5). This is especially true for denitrifying methanotrophs, because only a single enrichment culture has been described so far (7, 27).The objective of the present study was to generalize the previous finding that NC10 bacteria were associated with anaerobic methane oxidation, a necessary step forward in addressing the significance of this poorly understood process as a methane sink in freshwater habitats.  相似文献   
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The anaerobic ammonia-oxidizing activity of the planctomycete Candidatus "Brocadia anammoxidans" was not inhibited by NO concentrations up to 600 ppm and NO2 concentrations up to 100 ppm. B. anammoxidans was able to convert (detoxify) NO, which might explain the high NO tolerance of this organism. In the presence of NO2, the specific ammonia oxidation activity of B. anammoxidans increased, and Nitrosomonas-like microorganisms recovered an NO2-dependent anaerobic ammonia oxidation activity. Addition of NO2 to a mixed population of B. anammoxidans and Nitrosomonas induced simultaneous specific anaerobic ammonia oxidation activities of up to 5.5 mmol of NH4+ g of protein(-1) h(-1) by B. anammoxidans and up to 1.5 mmol of NH4+ g of protein(-1) h(-1) by Nitrosomonas. The stoichiometry of the converted N compounds (NO2-/NH3 ratio) and the microbial community structure were strongly influenced by NO2. The combined activity of B. anammoxidans and Nitrosomonas-like ammonia oxidizers might be of relevance in natural environments and for technical applications.  相似文献   
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