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1.
Fungal activity is a major driver in the global nitrogen cycle, and mounting evidence suggests that fungal denitrification activity contributes significantly to soil emissions of the greenhouse gas nitrous oxide (N2O). The metabolic pathway and oxygen requirement for fungal denitrification are different from those for bacterial denitrification. We hypothesized that the soil N2O emission from fungi is formate and O2 dependent and that land use and landforms could influence the proportion of N2O coming from fungi. Using substrate-induced respiration inhibition under anaerobic and aerobic conditions in combination with 15N gas analysis, we found that formate and hypoxia (versus anaerobiosis) were essential for the fungal reduction of 15N-labeled nitrate to 15N2O. As much as 65% of soil-emitted N2O was attributable to fungi; however, this was found only in soils from water-accumulating landforms. From these results, we hypothesize that plant root exudates could affect N2O production from fungi via the proposed formate-dependent pathway. 相似文献
2.
Qi Deng Dafeng Hui Junming Wang Stephen Iwuozo Chih-Li Yu Tigist Jima David Smart Chandra Reddy Sam Dennis 《PloS one》2015,10(4)
Background
A three-year field experiment was conducted to examine the responses of corn yield and soil nitrous oxide (N2O) emission to various management practices in middle Tennessee.Methodology/Principal Findings
The management practices include no-tillage + regular applications of urea ammonium nitrate (NT-URAN); no-tillage + regular applications of URAN + denitrification inhibitor (NT-inhibitor); no-tillage + regular applications of URAN + biochar (NT-biochar); no-tillage + 20% applications of URAN + chicken litter (NT-litter), no-tillage + split applications of URAN (NT-split); and conventional tillage + regular applications of URAN as a control (CT-URAN). Fertilizer equivalent to 217 kg N ha-1 was applied to each of the experimental plots. Results showed that no-tillage (NT-URAN) significantly increased corn yield by 28% over the conventional tillage (CT-URAN) due to soil water conservation. The management practices significantly altered soil N2O emission, with the highest in the CT-URAN (0.48 mg N2O m-2 h-1) and the lowest in the NT-inhibitor (0.20 mg N2O m-2 h-1) and NT-biochar (0.16 mg N2O m-2 h-1) treatments. Significant exponential relationships between soil N2O emission and water filled pore space were revealed in all treatments. However, variations in soil N2O emission among the treatments were positively correlated with the moisture sensitivity of soil N2O emission that likely reflects an interactive effect between soil properties and WFPS.Conclusion/Significance
Our results indicated that improved fertilizer and soil management have the potential to maintain highly productive corn yield while reducing greenhouse gas emissions. 相似文献3.
Role of Microorganisms in Emission of Nitrous Oxide and Methane in Pulse Cultivated Soil Under Laboratory Incubation Condition 总被引:1,自引:0,他引:1
Jyotsnarani Jena Sanak Ray Haragobinda Srichandan Anuradha Das Trupti Das 《Indian journal of microbiology》2013,53(1):92-99
Soil from a pulse cultivated farmers land of Odisha, India, have been subjected to incubation studies for 40 consecutive days, to establish the impact of various nitrogenous fertilizers and water filled pore space (WFPS) on green house gas emission (N2O & CH4). C2H2 inhibition technique was followed to have a comprehensive understanding about the individual contribution of nitrifiers and denitrifiers towards the emission of N2O. Nevertheless, low concentration of C2H2 (5 ml: flow rate 0.1 kg/cm2) is hypothesized to partially impede the metabolic pathways of denitrifying bacterial population, thus reducing the overall N2O emission rate. Different soil parameters of the experimental soil such as moisture, total organic carbon, ammonium content and nitrate–nitrogen contents were measured at regular intervals. Application of external N-sources under different WFPS conditions revealed the diverse role played by the indigenous soil microorganism towards green house gas emission. Isolation of heterotrophic microorganisms (Pseudomonas) from the soil samples, further supported the fact that denitrification might be prevailing during specific conditions thus contributing to N2O emission. Statistical analysis showed that WFPS was the most influential parameter affecting N2O formation in soil in absence of an inhibitor like C2H2. 相似文献
4.
Effects of Climate Change Drivers on Nitrous Oxide Fluxes in an Upland Temperate Grassland 总被引:1,自引:0,他引:1
Amélie A. M. Cantarel Juliette M. G. Bloor Nicolas Deltroy Jean-François Soussana 《Ecosystems》2011,14(2):223-233
Despite increasing interest in the patterns of trace gas emissions in terrestrial ecosystems, little is known about the impacts
of climate change on nitrous oxide (N2O) fluxes. The aim of this study was to determine the importance of the three main drivers of climate change (warming, summer
drought, and elevated CO2 concentrations) on N2O fluxes from an extensively managed, upland grassland. Over a 2-year period, we monitored N2O fluxes in an in situ ecosystem manipulation experiment simulating the climate predicted for the study area in 2080 (3.5°C
temperature increase, 20% reduction in summer rainfall and atmospheric CO2 levels of 600 ppm). N2O fluxes showed significant seasonal and interannual variation irrespective of climate treatment, and were higher in summer
and autumn compared with winter and spring. Overall, N2O emissions showed a positive correlation with soil temperature and rainfall. Elevated temperature had a positive impact on
mean annual N2O fluxes but effects were only significant in 2007. Contrary to expectations, neither combined summer drought and warming
nor the simultaneous application of elevated atmospheric CO2 concentrations, summer drought and warming had any significant effect on annual N2O fluxes. However, the maximum N2O flux rates observed during the study occurred when elevated CO2 was combined with warming and drought, suggesting the potential for important, short-term N2O–N losses in enriched CO2 environments. Taken together, our results suggest that the N2O responses of temperate, extensively managed grasslands to future climate change scenarios may be primarily driven by temperature
effects. 相似文献
5.
Nitrous Oxide Production and Methane Oxidation by Different Ammonia-Oxidizing Bacteria 总被引:4,自引:2,他引:4
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Ammonia-oxidizing bacteria (AOB) are thought to contribute significantly to N2O production and methane oxidation in soils. Most of our knowledge derives from experiments with Nitrosomonas europaea, which appears to be of minor importance in most soils compared to Nitrosospira spp. We have conducted a comparative study of levels of aerobic N2O production in six phylogenetically different Nitrosospira strains newly isolated from soils and in two N. europaea and Nitrosospira multiformis type strains. The fraction of oxidized ammonium released as N2O during aerobic growth was remarkably constant (0.07 to 0.1%) for all the Nitrosospira strains, irrespective of the substrate supply (urea versus ammonium), the pH, or substrate limitation. N. europaea and Nitrosospira multiformis released similar fractions of N2O when they were supplied with ample amounts of substrates, but the fractions rose sharply (to 1 to 5%) when they were restricted by a low pH or substrate limitation. Phosphate buffer (versus HEPES) doubled the N2O release for all types of AOB. No detectable oxidation of atmospheric methane was detected. Calculations based on detection limits as well as data in the literature on CH4 oxidation by AOB bacteria prove that none of the tested strains contribute significantly to the oxidation of atmospheric CH4 in soils. 相似文献
6.
Nitrous Oxide Emission Associated with Autotrophic Ammonium Oxidation in Acid Coniferous Forest Soil 总被引:1,自引:3,他引:1
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Pertti J. Martikainen 《Applied microbiology》1985,50(6):1519-1525
Aerobic N2O production was studied in nitrifying humus from urea-fertilized pine forest soil. Acetylene and nitrapyrin inhibited both NH4+ oxidation and N2O production, indicating that N2O production was closely associated with autotrophic NH4+ oxidation. N2O production was enhanced by low soil pH; it was negligible above pH 4.7. When soil pH decreased from 4.7 to 4.1, the relative amount of N2O-N produced from NH4+-N oxidized increased exponentially to 20%. There was also some evidence that N2O formation was stimulated by salts (potassium sulfate and sodium phosphates). The maximum rate of N2O-N production was 0.17 μg of N2O-N per g of soil per h. When humus was treated with NO2−, N2O evolved immediately, indicating chemical formation, but no N2O was formed on the addition of NO3−. The amount of N2O-N evolved was 0.6 to 4.6% of NO2−-N added. A high concentration of NO2− and low soil pH enhanced chemical production of N2O. There was no accumulation of NO2− during nitrification. The calculations indicated that chemical formation of N2O was not the main source of N2O during NH4+ oxidation. After the addition of inhibitors of NH4+ oxidation the soils contained NO3−, but no N2O was produced. The results suggest that enhanced autotrophic NH4+ oxidation is a potential source of N2O in fertilized acid forest soil. 相似文献
7.
8.
Separate Nitrite, Nitric Oxide, and Nitrous Oxide Reducing Fractions from Pseudomonas perfectomarinus 总被引:8,自引:1,他引:8
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Pseudomonas perfectomarinus was found to grow anaerobically at the expense of nitrate, nitrite, or nitrous oxide but not chlorate or nitric oxide. In several repetitive experiments, anaerobic incubation in culture media containing nitrate revealed that an average of 82% of the cells in aerobically grown populations were converted to the capacity for respiration of nitrate. Although they did not form colonies under these conditions, the bacteria synthesized the denitrifying enzymes within 3 hr in the absence of oxygen or another acceptable inorganic oxidant. This was demonstrated by the ability, after anaerobic incubation, of cells and of extracts to reduce nitrite, nitric oxide, and nitrous oxide to nitrogen. From crude extracts of cells grown on nitrate, nitrite, or nitrous oxide, separate complex fractions were obtained that utilized reduced nicotinamide adenine dinucleotide as the source of electrons for the reduction of (i) nitrite to nitric oxide, (ii) nitric oxide to nitrous oxide, and (iii) nitrous oxide to nitrogen. Gas chromatographic analyses revealed that each of these fractions reduced only one of the nitrogenous oxides. 相似文献
9.
The fungus Fusarium oxysporum 11dn1 was found to be able to grow and produce nitrous oxide on nitrate-containing medium in anaerobic conditions. The rate of nitrous oxide formation was three to six orders of magnitude lower than the rates of molecular nitrogen production by common denitrifying bacteria. Acetylene and ammonia did not affect the release of nitrous oxide release. It was shown that under anaerobic conditions fast increase of nitrate reductase activity occurred, caused by the synthesis of enzyme de novo and protein dephosphorylation. Reverse transfer of the mycelium to aerobic conditions led to a decline in nitrate reductase activity and stopped nitrous oxide production. The presence of two nitrate reductases was shown, which differed in molecular mass, location, temperature optima, and activity in nitrate- and ammonium-containing media. Two enzymes represent assimilatory and dissimilatory nitrate reductases, which are active in aerobic and anaerobic conditions, respectively. Received: 2 February 2000 / Accepted: 28 February 2000 相似文献
10.
Pia K. Wüst Marcus A. Horn Gemma Henderson Peter H. Janssen Bernd H. A. Rehm Harold L. Drake 《Applied and environmental microbiology》2009,75(11):3430-3436
Previous studies have documented the capacity of European earthworms belonging to the family Lumbricidae to emit the greenhouse gas nitrous oxide (N2O), an activity attributed primarily to the activation of ingested soil denitrifiers. To extend the information base to earthworms in the Southern Hemisphere, four species of earthworms in New Zealand were examined for gut-associated denitrification. Lumbricus rubellus and Aporrectodea rosea (introduced species of Lumbricidae) emitted N2O, whereas emission of N2O by Octolasion cyaneum (an introduced species of Lumbricidae) and emission of N2O by Octochaetus multiporus (a native species of Megascolecidae) were variable and negligible, respectively. Exposing earthworms to nitrite or nitrate and acetylene significantly increased the amount of N2O emitted, implicating denitrification as the primary source of N2O and indicating that earthworms emitted dinitrogen (N2) in addition to N2O. The alimentary canal displayed a high capacity to produce N2O when it was supplemented with nitrite, and alimentary canal contents contained large amounts of carbohydrates and organic acids indicative of fermentation (e.g., succinate, acetate, and formate) that could serve as sources of reductant for denitrification. nosZ encodes a portion of the terminal oxidoreductase used in denitrification. The nosZ sequences detected in the alimentary canals of L. rubellus and O. multiporus were similar to those retrieved from soil and were distantly related to sequences of uncultured soil bacteria and genera common in soils (i.e., Bradyrhizobium, Azospirillum, Rhodopseudomonas, Rhodospirillum, Pseudomonas, Oligotropha, and Sinorhizobium). These findings (i) suggest that the capacity to emit N2O and N2 is a general trait of earthworms and not geographically restricted, (ii) indicate that species belonging to different earthworm families (i.e., Megascolecidae and Lumbricidae) may not have equal capacities to emit N2O, and (iii) also corroborate previous findings that link this capacity to denitrification in the alimentary canal.Earthworms are dominant members of the soil fauna and affect the structure and fertility of soils (5, 20, 22, 23). Various species of European earthworms belonging to the family Lumbricidae (e.g., Aporrectodea caliginosa, Lumbricus rubellus, and Octolasion lacteum) emit dinitrogen (N2) and the greenhouse gas nitrous oxide (N2O), and their burrowing activities and feeding habits in combination with in situ conditions can influence the emission of nitrogenous gases from soils that they inhabit (1, 2, 13, 17, 25, 27, 39).The microbiology of the earthworm alimentary canal has been addressed in numerous studies (3, 4, 6, 9, 14, 16, 32). The alimentary canal of the earthworm is anoxic, in marked contrast to the aerated material that earthworms ingest (14, 39). Anoxia and other in situ conditions of the alimentary canal appear to stimulate soil microbes capable of surviving under anaerobic conditions during passage through the gut (3, 4). Soils are rich in denitrifying bacteria (37), and the capacity of European earthworms to emit nitrogenous gases has been attributed primarily to the in situ activity of ingested denitrifying bacteria that appear to be highly active under the anoxic conditions of the earthworm alimentary canal (12, 15, 17, 25, 39). However, it is not known if the capacity to emit nitrogenous gases is a general trait of earthworms independent of their taxonomic family or geographic location. The main objectives of this study were to examine the capacity of Southern Hemisphere earthworms in New Zealand to emit N2O and to determine if this capacity was linked to denitrifying bacteria in the alimentary canal. 相似文献
11.
《BMJ (Clinical research ed.)》1970,1(5698):709-713
Trials have been organized by a Medical Research Council committee to assess the effectiveness and safety for analgesia in labour of oxygen and nitrous oxide mixtures in different proportions. In a preliminary trial concentrations of 50% and 60% v/v nitrous oxide were compared, but, as the replies of 409 mothers revealed little difference between the two, the results of administering either 50% or 70% nitrous oxide to 778 mothers were then compared. The data relating to normal labour, obtained on 501 of the mothers in this main trial, showed that the relief of pain given was much the same. There was a suggestion, however, that the higher concentration of nitrous oxide might be useful in abnormal labour. The proportion of mothers with normal deliveries who lost consciousness, though very small, was significantly higher with 70% nitrous oxide than with the lower concentration. Ninety-two per cent. of mothers found the gas and oxygen machine helpful, and midwives reported complete or good co-operation by 77% of those using it. It is concluded that the 50% oxygen and 50% nitrous oxide mixture can safely be used by unsupervised midwives. 相似文献
12.
Temporal Change in Nitrous Oxide and Dinitrogen from Denitrification Following Onset of Anaerobiosis 总被引:3,自引:6,他引:3
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Similar temporal patterns were found in three mineral soils for the composition of the gaseous products of denitrification following the onset of anaerobic conditions. During the early period of anaerobiosis (0 up to 1 to 3 h), N2 was the dominant product of denitrification. The NO3− → N2O activity then increased, but was not accompanied by a corresponding increase in N2O-reducing activity. This resulted in a relatively extended period of time (1 to 3 up to 16 to 33 h) during which N2O was a major product. Eventually (after 16 to 33 h), an increase in N2O-reducing activity occurred without a comparable increase in the N2O-producing activity. The increase in the rate of N2O reduction did not occur in the presence of chloramphenicol and required the presence of N2O or NO3− during the preceding anaerobic incubation. During the final period (16 to 33, up to 48 h), N2 was generally the sole product of denitrification, since the rate of N2O reduction exceeded the rate of N2O production. A similar sequential pattern was also found for a culture of a denitrifying Flavobacterium sp. shifted to anaerobic growth. A staggered synthesis of the enzymes in the denitrification sequence apparently occurred in response to anoxia, which caused first a net production of N2O followed by consumption of N2O. 相似文献
13.
The Impact of Using Mature Compost on Nitrous Oxide Emission and the Denitrifier Community in the Cattle Manure Composting Process 总被引:8,自引:0,他引:8
The diversity and dynamics of the denitrifying genes (nirS, nirK, and nosZ) encoding nitrite reductase and nitrous oxide (N2O) reductase in the dairy cattle manure composting process were investigated. A mixture of dried grass with a cattle manure
compost pile and a mature compost-added pile were used, and denaturing gradient gel electrophoresis was used for denitrifier
community analysis. The diversity of nirK and nosZ genes significantly changed in the initial stage of composting. These variations might have been induced by the high temperature.
The diversity of nirK was constant after the initial variation. On the other hand, the diversity of nosZ changed in the latter half of the process, a change which might have been induced by the accumulation of nitrate and nitrite.
The nirS gene fragments could not be detected. The use of mature compost that contains nitrate and nitrite promoted the N2O emission and significantly affected the variation of nosZ diversity in the initial stage of composting, but did not affect the variation of nirK diversity. Many Pseudomonas-like nirK and nosZ gene fragments were detected in the stage in which N2O was actively emitted. 相似文献
14.
Evidence for Involvement of Gut-Associated Denitrifying Bacteria in Emission of Nitrous Oxide (N2O) by Earthworms Obtained from Garden and Forest Soils
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Carola Matthies Anja Grießhammer Martina Schmittroth Harold L. Drake 《Applied microbiology》1999,65(8):3599-3604
Earthworms (Aporrectodea caliginosa, Lumbricus rubellus, and Octolasion lacteum) obtained from nitrous oxide (N2O)-emitting garden soils emitted 0.14 to 0.87 nmol of N2O h−1 g (fresh weight)−1 under in vivo conditions. L. rubellus obtained from N2O-emitting forest soil also emitted N2O, which confirmed previous observations (G. R. Karsten and H. L. Drake, Appl. Environ. Microbiol. 63:1878–1882, 1997). In contrast, commercially obtained Lumbricus terrestris did not emit N2O; however, such worms emitted N2O when they were fed (i.e., preincubated in) garden soils. A. caliginosa, L. rubellus, and O. lacteum substantially increased the rates of N2O emission of garden soil columns and microcosms. Extrapolation of the data to in situ conditions indicated that N2O emission by earthworms accounted for approximately 33% of the N2O emitted by garden soils. In vivo emission of N2O by earthworms obtained from both garden and forest soils was greatly stimulated when worms were moistened with sterile solutions of nitrate or nitrite; in contrast, ammonium did not stimulate in vivo emission of N2O. In the presence of nitrate, acetylene increased the N2O emission rates of earthworms; in contrast, in the presence of nitrite, acetylene had little or no effect on emission of N2O. In vivo emission of N2O decreased by 80% when earthworms were preincubated in soil supplemented with streptomycin and tetracycline. On a fresh weight basis, the rates of N2O emission of dissected earthworm gut sections were substantially higher than the rates of N2O emission of dissected worms lacking gut sections, indicating that N2O production occurred in the gut rather than on the worm surface. In contrast to living earthworms and gut sections that produced N2O under oxic conditions (i.e., in the presence of air), fresh casts (feces) from N2O-emitting earthworms produced N2O only under anoxic conditions. Collectively, these results indicate that gut-associated denitrifying bacteria are responsible for the in vivo emission of N2O by earthworms and contribute to the N2O that is emitted from certain terrestrial ecosystems. 相似文献
15.
Distinguishing Nitrous Oxide Production from Nitrification and Denitrification on the Basis of Isotopomer Abundances 总被引:3,自引:0,他引:3
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R. L. Sutka N. E. Ostrom P. H. Ostrom J. A. Breznak H. Gandhi A. J. Pitt F. Li 《Applied microbiology》2006,72(1):638-644
The intramolecular distribution of nitrogen isotopes in N2O is an emerging tool for defining the relative importance of microbial sources of this greenhouse gas. The application of intramolecular isotopic distributions to evaluate the origins of N2O, however, requires a foundation in laboratory experiments in which individual production pathways can be isolated. Here we evaluate the site preferences of N2O produced during hydroxylamine oxidation by ammonia oxidizers and by a methanotroph, ammonia oxidation by a nitrifier, nitrite reduction during nitrifier denitrification, and nitrate and nitrite reduction by denitrifiers. The site preferences produced during hydroxylamine oxidation were 33.5 ± 1.2‰, 32.5 ± 0.6‰, and 35.6 ± 1.4‰ for Nitrosomonas europaea, Nitrosospira multiformis, and Methylosinus trichosporium, respectively, indicating similar site preferences for methane and ammonia oxidizers. The site preference of N2O from ammonia oxidation by N. europaea (31.4 ± 4.2‰) was similar to that produced during hydroxylamine oxidation (33.5 ± 1.2‰) and distinct from that produced during nitrifier denitrification by N. multiformis (0.1 ± 1.7‰), indicating that isotopomers differentiate between nitrification and nitrifier denitrification. The site preferences of N2O produced during nitrite reduction by the denitrifiers Pseudomonas chlororaphis and Pseudomonas aureofaciens (−0.6 ± 1.9‰ and −0.5 ± 1.9‰, respectively) were similar to those during nitrate reduction (−0.5 ± 1.9‰ and −0.5 ± 0.6‰, respectively), indicating no influence of either substrate on site preference. Site preferences of ~33‰ and ~0‰ are characteristic of nitrification and denitrification, respectively, and provide a basis to quantitatively apportion N2O. 相似文献
16.
Ecosystems - Nitrous oxide (N2O) is a major greenhouse gas and cultivated soils are the most important anthropogenic source. N2O production and consumption are known to occur at depths below the A... 相似文献
17.
Tillage and Nitrogen Application Effects on Nitrous and Nitric Oxide Emissions from Irrigated Corn Fields 总被引:3,自引:0,他引:3
A 2-year study was conducted to investigate the potential of no-till cropping systems to reduce N2O and NO emissions under different N application rates in an irrigated corn field in northeastern Colorado. Flux measurements
were begun in the spring of 2003, using vented (N2O) and dynamic (NO) chambers, one to three times per week, year round, within plots that were cropped continuously to corn
(Zea mays L.) under conventional-till (CT) and no-till (NT). Plots were fertilized at planting in late April with rates of 0, 134 and
224 kg N ha−1 and corn was harvested in late October or early November each year. N2O and NO fluxes increased linearly with N application rate in both years. Compared with CT, NT did not significantly affect
the emission of N2O but resulted in much lower emission of NO. In 2003 and 2004 corn growing seasons, the increase in N2O-N emitted per kg ha−1 of fertilizer N added was 14.5 and 4.1 g ha−1 for CT, and 11.2 and 5.5 g ha−1 for NT, respectively. However, the increase in NO-N emitted per kg ha−1 of fertilizer N added was only 3.6 and 7.4 g ha−1 for CT and 1.6 and 2.0 g ha−1 for NT in 2003 and 2004, respectively. In the fallow season (November 2003 to April 2004), much greater N2O (2.0–3.1 times) and NO (13.1–16.8 times) were emitted from CT than from NT although previous N application did not show
obvious carry-over effect on both gas emissions. Results from this study reveal that NT has potential to reduce NO emission
without an obvious change in N2O emission under continuous irrigated corn cropping compared to CT. 相似文献
18.
Mette Kolpen Michael Kühl Thomas Bjarnsholt Claus Moser Christine R?nne Hansen Lars Liengaard Arsalan Kharazmi Tanja Pressler Niels H?iby Peter ?strup Jensen 《PloS one》2014,9(1)
Chronic lung infection by Pseudomonas aeruginosa is the major severe complication in cystic fibrosis (CF) patients, where P. aeruginosa persists and grows in biofilms in the endobronchial mucus under hypoxic conditions. Numerous polymorphonuclear leukocytes (PMNs) surround the biofilms and create local anoxia by consuming the majority of O2 for production of reactive oxygen species (ROS). We hypothesized that P. aeruginosa acquires energy for growth in anaerobic endobronchial mucus by denitrification, which can be demonstrated by production of nitrous oxide (N2O), an intermediate in the denitrification pathway. We measured N2O and O2 with electrochemical microsensors in 8 freshly expectorated sputum samples from 7 CF patients with chronic P. aeruginosa infection. The concentrations of NO3
− and NO2
− in sputum were estimated by the Griess reagent. We found a maximum median concentration of 41.8 µM N2O (range 1.4–157.9 µM N2O). The concentration of N2O in the sputum was higher below the oxygenated layers. In 4 samples the N2O concentration increased during the initial 6 h of measurements before decreasing for approximately 6 h. Concomitantly, the concentration of NO3
− decreased in sputum during 24 hours of incubation. We demonstrate for the first time production of N2O in clinical material from infected human airways indicating pathogenic metabolism based on denitrification. Therefore, P. aeruginosa may acquire energy for growth by denitrification in anoxic endobronchial mucus in CF patients. Such ability for anaerobic growth may be a hitherto ignored key aspect of chronic P. aeruginosa infections that can inform new strategies for treatment and prevention. 相似文献
19.
Denitrifying Bacteria in the Earthworm Gastrointestinal Tract and In Vivo Emission of Nitrous Oxide (N(inf2)O) by Earthworms
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Earthworms (Lumbricus rubellus and Octolasium lacteum) and gut homogenates did not produce CH(inf4), and methanogens were not readily culturable from gut material. In contrast, the numbers of culturable denitrifiers averaged 7 x 10(sup7) and 9 x 10(sup6) per g (dry weight) of gut material for L. rubellus and O. lacteum, respectively; these values were 256- and 35-fold larger than the numbers of culturable denitrifiers in the soil from which the earthworms were obtained. Anaerobically incubated earthworm gut homogenates supplemented with nitrate produced N(inf2)O at rates exceeding that of soil homogenates. Furthermore, living earthworms emitted N(inf2)O under aerobic conditions, and N(inf2)O emission was stimulated by acetylene. For earthworms collected from a mildly acidic (pH 6) beech forest soil, the rates of N(inf2)O emission for earthworms and soil averaged 884 and 2 pmol per h per g (fresh weight), respectively. In contrast, for earthworms collected from a more acidic (pH 4.6) oak-beech forest soil, N(inf2)O emission by earthworms and soil averaged 145 and 45 pmol per h per g (fresh weight), respectively. Based on the extrapolation of this data, earthworms accounted for an estimated 16 and 0.25% of the total N(inf2)O produced at the stand level of these beech and oak-beech forest soils, respectively. 相似文献
20.
Josette Garnier Aurélie Cébron Gaëlle Tallec Gilles Billen Mathieu Sebilo Anun Martinez 《Biogeochemistry》2006,77(3):305-326
The Seine River estuary (France) is the receptacle of a drainage basin characterised by high population density, heavy industrial
activity and intensive agriculture. Whereas nitrate concentrations are high due to diffuse sources in the upstream drainage
basin, ammonium mainly originates from the effluents of the Achères wastewater treatment plant (WWTP) downstream from Paris
and its suburbs (6.5 million equivalent-inhabitants). Ammonium is mostly nitrified in the tidal freshwater estuary and nitrification
causes a strong summer oxygen deficit. Average longitudinal summer profiles of oxygen and nitrogen concentrations for two
periods, between 1993–1997 and 1998–2003 in dry hydrological conditions (excluding the wet years 2000 and 2001) clearly reflect
the changes due to the improved treatment of wastewater from Paris and its suburbs. On the basis of daily water flux data
and twice monthly nitrogen measurements at the boundaries of the upstream freshwater estuarine section (108 km), we calculated
nitrification and denitrification fluxes, whose annual averages were 43 and 71 × 103 kg N d−1 respectively from 1993 to 2003, with summer values (July–September) representing 73 and 57% of the annual fluxes, respectively.
The degree of denitrification in the upper estuary appears to be closely related to the nitrification, itself more loosely
related to the amount of reduced nitrogen (Kjeldahl) brought by the treated effluents from the Achères WWTP. We estimated
the total N2O emissions to about 40 kg N d−1 (25–60 kg N d−1) in the same sector. 相似文献