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1.
Denitrification in sediment determined from nitrogen isotope pairing 总被引:29,自引:0,他引:29
Lars Peter Nielsen 《FEMS microbiology letters》1992,86(4):357-362
Abstract A new method for accurate and easy measurement of denitrification in sediments is presented. The water overlying intact sediment cores was enriched with 15 NO3 − which mixed with the 14 NO3 − of the natural sources of NO3 − . The formation by denitrification of single-labeled (14 N15 N) and double-labeled (15 N15 N) dinitrogen pairs was measured by mass spectrometry after a few hours incubation. Total denitrification including the formation of unlabeled (14 N14 N) dinitrogen could be calculated assuming random isotope pairing by denitrification of the uniformly mixed NO3 − species. In contrast to previous approaches, by this method it is possible to measure denitrification of both NO3 − diffusing from the overlying water and NO3 − from nitrification within the sediment. 相似文献
2.
Effects of nitrate, chloride and chlorate ions upon nitrate and chlorate uptake by roots of maize ( Zea mays L., cv. B73) seedlings were examined. Net nitrate uptake, 36 ClO3 − influx and 36 Cl− influx (the latter two in a background of 0.5 m M KNO3 ) displayed similar pH profiles with optima at pH 5.5 and below. External, non-labeled chloride had little effect on the accumulation of 36 ClO3 − (both in 5 h and 20 min uptake assays), while nitrate and chlorate had almost identical, marked inhibitory effects. Nitrate pretreatment caused an apparent induction of both 36 ClO3 − and 15 NO3 − uptake activities. After 5 h of treatment in nitrate, the uptake activities of chloride- and chlorate-pretreated plants increased to that of nitrate-pretreated plants. During 6 h exposure to chlorate, 36 ClO3 − uptake activity of nitrate-pretreated plants decreased to that of chlorate- and chloride-pretreated plants. The results support the existence of a shared nitrate/chlorate transport system in maize roots which is not inhibited by external chloride, and which is induced by nitrate, but not by chlorate or chloride. The suggestion is made that selection of chlorate-resistant mutants of maize can identify nitrate uptake as well as nitrate reductase mutants. 相似文献
3.
Effects of oxygen, pH and nitrate concentration on denitrification by Pseudomonas species 总被引:2,自引:0,他引:2
Abstract The production of nitrogen-containing gases by denitrification in three organisms was examined using membrane inlet mass spectrometry. The effects of O2 (during both growth and maintenance) and of pH, nitrate concentration and carbon source were tested in non-proliferating cell suspensions. Two strains of Pseudomonas aeruginosa were capable of co-respiration of NO3 − and O2 and, under controlled O2 supply, gave oscillatory denitrification. Variations in culture and assay conditions affected both the rate of denitrification and the ratio of end products (N2 O:N2 ). Higher rates were seen following anaerobic growth. Optimum values of pH and nitrate concentration for denitrification are given. Generally, the optimum pH was 7.0–7.5, approximately that of the growth medium. Optimum nitrate concentration was generally 20 mM. 相似文献
4.
Oxygen control prevents denitrifiers and barley plant roots from directly competing for nitrate 总被引:1,自引:0,他引:1
Abstract Two denitrifying bacteria ( Pseudomonas chlororaphis and P. aureofaciens ) and a plant (barley, Hordeum vulgare ) were used to study the effect of O2 concentration on denitrification and NO3 − uptake by roots under well-defined aeration conditions. Bacterial cells in the early stationary phase were kept in a chemostat vessel with vigorous stirring and thus a uniform O2 concentration in the solution. Both Pseudomonads lacked N2 O reductase and so total denitrification could be directly measured as N2 O production.
Denitrification decreased to 6–13% of the anaerobic rate at 0.01% O2 saturation (0.14 μM O2 ) and was totally inhibited at 0.04% O2 saturation (0.56 μM O2 ). In this well-mixed system denitrification was 10-times more oxygen sensitive than stated in earlier reports. Uptake of nitrate by plants was measured in the same system under light. The NO3 − uptake rate decreased gradually from a maximum in 21% O2 -saturated medium (air saturated) to zero at 1.6% O2 saturation (22.4 μM O2 ). Owing to the very different non-overlapping oxygen requirements of the two processes, direct competition for nitrate between plant roots and denitrifying bacteria cannot occur. 相似文献
Denitrification decreased to 6–13% of the anaerobic rate at 0.01% O
5.
Nitrate assimilation and nitrogen circulation in Austrian pine 总被引:2,自引:0,他引:2
Nitrate uptake, reduction and translocation were examined in 5-week-old Austrian pines ( Pinus nigra Arnold var. nigricans Host.) during exposure to 5 m M NaNO3 . The rate of nitrate uptake was linear during the 7 h light period. 15 N-NO3 − was detected in all parts of the pine except in the needles. By the 7th hour, 43% of the absorbed nitrate had been reduced, and this increased to 64% by the 24th hour. The major part of the total reduction occurred in the roots at this growth stage. Accumulation of 15 N in reduced soluble and insoluble fractions was more prevalent in roots than in shoots. In the needles, the translocated nitrogen was mainly incorporated into the insoluble fraction. It is likely that most of the nitrogen from nitrate was transported from the roots to the aerial organs as organic nitrogen; however part of the upward nitrogen flux took place as nitrate ions.
An experiment in which an exposure for 24 h to 5 m M Na15 NO3 was followed by 13 days exposure to Na14 NO3 (pulse chase experiment) revealed a half time of about 1 day for depletion of root nitrate. A large part of this depletion was due to the loss of 15 N-NO3 − to the nutrient solution. The remaining pool of 15 N-nitrate was partitioned between a metabolically inactive and an active pool. During the chase period, the simultaneous decrease of 15 N-incorporation in the soluble N fraction and increase in the insoluble N fraction in different pine parts, particularly in the needles, suggested that protein synthesis occurred mostly in young tissues of the shoot and was the major sink of the newly absorbed 15 N-NO3 . 相似文献
An experiment in which an exposure for 24 h to 5 m M Na
6.
Nitrification and denitrification by Thiosphaera pantotropha in aerobic chemostat cultures 总被引:4,自引:0,他引:4
Abstract: Thiosphaera pantotropha has been reported to denitrify aerobically and nitrify heterotrophically. However, recent evidence has indicated that these properties (particularly aerobic denitrification) have been lost. The occurrence and levels of aerobic denitrification and heterotrophic nitrification by T. pantotropha in chemostat cultures have therefore been re-evaluated. Only low nitrate reduction rates were observed: the apparent nitrogen loss was of the same order of magnitude as the combined error in the calculated nitrogen consumption. However, 15 N mass spectrometry revealed low aerobic denitrification rates (about 10% of the rates originally published by this group). Heterotrophic nitrification rates were about a third of previous observations. N2 and N2 O were both produced from NH4 + , NO3 − and NO2 − . Periplasmic nitrate reductase was present in aerobically grown cells. 相似文献
7.
Lesley A. Robertson Tage Dalsgaard Niels-Peter Revsbech J.Gijs Kuenen 《FEMS microbiology ecology》1995,18(2):113-120
Abstract: Because of a revival in the controversy surrounding 'aerobic denitrification', especially in relation to Thiosphaera pantotropha , activity in aerobic batch cultures was evaluated using gas chromatography and mass spectrometry after the addition of 15 N-labelled NH4 + and NO2 − . Aerobic denitrifying activity in T. pantotropha was present, but only at about 10% of the originally-reported levels. The activity of ' Pseudomonas denitrificans ' was similar to previously-reported values. Alcaligenes faecalis showed significant aerobic denitrifying activity, producing almost equivalent amounts of N2 and N2 O. An unidentified pseudomonad, isolate G4, presumably requires anoxia for enzyme activity as it did not denitrify aerobically, even though it has a constitutive denitrifying pathway. 相似文献
8.
Interactive effects of elevated atmospheric CO2 and arbuscular mycorrhizal (AM) fungi on biomass production and N2 fixation were investigated using black locust ( Robinia pseudoacacia ). Seedlings were grown in growth chambers maintained at either 350 μmol mol−1 or 710 μmol mol−1 CO2 . Seedlings were inoculated with Rhizobium spp. and were grown with or without AM fungi. The 15 N isotope dilution method was used to determine N source partitioning between N2 fixation and inorganic fertilizer uptake. Elevated atmospheric CO2 significantly increased the percentage of fine roots that were colonized by AM fungi. Mycorrhizal seedlings grown under elevated CO2 had the greatest overall plant biomass production, nodulation, N and P content, and root N absorption. Additionally, elevated CO2 levels enhanced nodule and root mass production, as well as N2 fixation rates, of non- mycorrhizal seedlings. However, the relative response of biomass production to CO2 enrichment was greater in non-mycorrhizal seedlings than in mycorrhizal seedlings. This study provides strong evidence that arbuscular mycorrhizal fungi play an important role in the extent to which plant nutrition of symbiotic N2 -fixing tree species is affected by enriched atmospheric CO2 . 相似文献
9.
Abstract A methanotrophic nitrifying consortium was previously obtained from a humisol which showed CH4 -dependent nitrification. Although the methanotroph could not be obtained in pure culture, three other members of the consortium have been isolated: An obligately methylotrophic Methylobacillus (Is-1) which grows only on CH3 OH and does not nitrify; a Pseudomonas (Is-2) which grows on Is-1 culture filtrate and produces NO2 − , NO3 − and N2 O from NH2 OH, and NO3 − from NO2 − ; and a second Pseudomonas (Is-3) which produces NO3 − from NH4 + or NO2 − , and N2 O from NH2 OH. A model is proposed for the trophic relations and nitrogen transformations in the consortium which may apply to some natural systems. 相似文献
10.
Denitrification and nitrate-reducing bacterial populations in abandoned and reclaimed minesoils 总被引:1,自引:0,他引:1
Abstract Microbial populations, nitrogen mineralization potentials, and denitrification enzyme activities were examined in two abandoned carbolithic minesoils. Numbers and activities of bacteria and fungi were lower in nonamended than in lime and/or fly ash amended sites. Rates of aerobic NO3 − production (3 to 38 μg-N kg−1 h−1 ) and anaerobic NO3 − reduction to N2 O (5 to 68 μg-N kg−1 h−1 ) were measured. Organisms capable of N2 O production under anaerobic soil conditions were present in low numbers, and their activity was restricted in part by low soil pH. Nondenitrifying nitrate-reducing bacteria were more diverse and in greater numbers than respiratory denitrifiers and may have been responsible for N2 O production in assays measuring denitrification enzyme activity. 相似文献
11.
Measurement of denitrification in estuarine sediment using membrane inlet mass spectrometry 总被引:1,自引:0,他引:1
Abstract Denitrification was measured in intact sediment cores and in homogenised slurries using membrane inlet mass spectrometry. Dissolved concentrations of O2 , N2 , N2 O and CO2 were simultaneously monitored. Using a 0.8 mm diameter needle probe, a comparison was made of the gas profiles of intact cores obtained under different conditions, i.e. with air or argon as the headspace gas and after the addition of nitrate and/or a carbon source to the sediment surface. O2 was detectable to a depth of 1 cm under a headspace of air and the depth at which the maxima of denitrification products occurred was 1.5–2 cm. Denitrification products (N2 O, N2 ) occurred in the surface layers where O2 was above the minimum level of detectability (> 0.25 μM): diffusion of N2 and N2 O upwards from the anoxic zone, local anaerobic microenvironments or aerobic denitrification are alternative explanations for this observation. The addition of nitrate and/or acetate increased the concentrations of N2 , N2 O and CO2 in the sediment core. In sediment slurries, the pH, nitrate concentration, carbon source and the depth from which the sample was taken affected the rate of denitrification. Nitrogen was the sole detectable end product. Maximum denitrification occurred at pH 7.5 and at 20 mM nitrate. Denitrification was at a maximum in those slurries prepared from sections of core at 1–2 cm depth. 相似文献
12.
Clones of Rosa damascena Mill. cv. Gloire de Guillan, selected for growth in solid medium containing 56 m M NaClO3 , were studied to determine the reason for their resistance to this toxic salt. The cells grew on medium containing nitrate as the only nitrogen source, and they synthesized nitrate reductase (EC 1.6.6.2) in the presence of nitrate. The cells were resistant in the presence of nitrate. However, their resistance was greatly increased by the presence of glutamate in the medium. The cells took up [36 Cl]-ClO3 - and reduced it to ClO2 − , but the fraction of ClO3 − that they reduced under our experimental conditions was less than that reduced by wild type. The slower production of ClO2 − apparently accounted for the resistance of the cells to ClO3 − . We suggest several possible reasons for the low rate of reduction of ClO3 − . 相似文献
13.
Methane-dependent nitrate production by a microbial consortium enriched from a cultivated humisol 总被引:2,自引:0,他引:2
Abstract A consortium was enriched from a humisol incubated with 3.6 kPa CH4 and NH4 + . This consortium oxidized NH4 + to NO2 − and NO3 − (NO3 − /NO2 − ratio about 20) with smaller amounts of N2 O. This oxidation stopped in the stationary phase after depletion of CH4 . CH3 OH or CO2 did not support oxidation. Growth and resting cell experiments suggested that nitrification was associated with methanotrophic activity and that chemoautotrophic nitrifiers were absent. 相似文献
14.
This study was designed to investigate whether the blood of Pagothenia borchgrevinki , exhibits a Haldane effect, and whether activation of a Na+ /H+ antiporter increases transport of intracellular protons and Bohr protons out of the erythrocytes resulting in inhibition of CO2 excretion in both P. borchgrevinki , and Dissostichus mawsoni. When carbon dioxide dissociation curves were determined from blood samples pooled from three fish under oxygenated and deoxygenated conditions a Haldane effect was observed. Using an in vitro , CO2 excretion assay, the rate of HCO3 − dehydration was determined on blood and plasma equilibrated under an N2 atmosphere then rapidly oxygenated with air in the presence of 10−5 M noradrenaline or acetazolamide (1004 M). Whole blood and plasma from P. borchgrevinki , and D. mawsoni , were equilibrated with 0·5% CO2 in air and assayed in the presence of 10−5 M noradrenaline. Erythrocyte CO2 excretion rates were depressed significantly by noradrenaline in both species. The whole blood HCO3 − dehydration rate was depressed significantly following rapid oxygenation in the presence of acetazolamide indicating that the pathway of CO2 excretion included activation of intracellular carbonic anhydrase and an adrenergic receptor. 相似文献
15.
Fixation of molecular nitrogen by Methanosarcina barkeri 总被引:1,自引:0,他引:1
Abstract Methanosarcina barkeri cells were observed in ammonia-free anaerobic acetate enrichments for sulfate-reducing bacteria. The capacity of Methanosarcina to grow diazotrophically was proved with a pure culture in mineral media with methanol. The cell yields with N2 or NH4 + ions as nitrogen source were 2.2 g and 6.1 g dry weight, respectively, per mol of methanol. Growth experiments with 15 N2 revealed that 84% of the cell nitrogen was derived from N2 . Acetylene was highly toxic to Methanosarcina and only reduced at concentrations lower than 100 μmol dissolved per 1 of medium. Assimilation of N2 and reduction of acetylene were inhibited by NH4 + ions. The experiments show that N2 fixation occurs not only in eubacteria but also in archaebacteria. The ecological significance of diazotrophic growth of Methanosarcina is discussed. 相似文献
16.
The nitrogen use efficiencies (NUE) of N2 fixation, primary NH 4 + assimilation and NO 3 − assimilation are compared. The photon and water costs of the various biochemical and transport processes involved in plant growth, N-assimilation, pH regulation and osmolarity generation, per unit N assimilated are respectively likely to be around 5 and 7% greater for N2 fixation than for a combination of NH 4 + and root and shoot NO 3 − assimilation as occurs with most crops. Studies on plant and rhizobial genes involved in nodulation and N2 fixation may lead to more rapid nodulation, production of more stress-tolerant N2 fixing systems and transfer of the hydrogenase system to rhizobium/legume symbioses which currently do not have this ability. The activity of an uptake hydrogenase is predicted to decrease the photon cost of diazotrophic plant growth by about 1%. 相似文献
17.
Symbiotic N2 fixation in a high Alpine grassland: effects of four growing seasons of elevated CO2 总被引:1,自引:0,他引:1
J. A. Arnone Iii 《Functional ecology》1999,13(3):383-387
1. Increasing carbon dioxide concentration (E: 680 μl CO2 litre–1 vs ambient, A: 355 μl CO2 litre–1 ) around late-successional Alpine sedge communities of the Swiss Central Alps (2450 m) for four growing seasons (1992–1995) had no detectable effect on symbiotic N2 fixation in Trifolium alpinum —the sole N2 -fixing plant species in these communities (74 ± 30 mg N m–2 year–1 , A and E plots pooled).
2. This result is based on data collected in the fourth growing season showing that elevated CO2 had no effect on Trifolium above-ground biomass (4·4 ± 1·7 g m–2 , A and E plots pooled, n = 24) or N content per unit land area (124 ± 51 mg N m–2 , A and E pooled), or on the percentage of N Trifolium derived from the atmosphere through symbiotic N2 fixation (%Ndfa: 61·0 ± 4·1 across A and E plots) estimated using the 15 N dilution method.
3. Thus, it appears that N inputs to this ecosystem via symbiotic N2 fixation will not be dramatically affected in the foreseeable future even as atmospheric CO2 continues to rise. 相似文献
2. This result is based on data collected in the fourth growing season showing that elevated CO
3. Thus, it appears that N inputs to this ecosystem via symbiotic N
18.
The microbial flora of smoked pork loin and frankfurter sausage stored in different gas atmospheres at 4°C 总被引:2,自引:2,他引:0
The development of the microflora of smoked pork loin and frankfurter sausage was followed during storage in vacuum, N2 and CO2 atmospheres at 4°C. The total aerobic count on the smoked pork loin reached 107 organisms/g after 37 d in vacuum, 43 d in N2 and 49 d in CO2 . The corresponding value for the sausage was 77 d in vacuum, while the growth stopped at 6 times 104 organisms/g after 98 d in N2 , and at 4 times 102 organisms/g after 48 d in CO2 .
The predominant organisms on the fresh products were Bacillus spp., coryneform bacteria, Flavobacterium spp. and Pseudomonas spp.
At the end of the storage time the microflora on both products in the three gas atmospheres, consisted mainly of Lactobacillus spp. and two large groups of organisms that could not be identified as any described genus. Some of the unidentified strains could be classified as a Lactobacillus sp. after subsequent subculturing on laboratory media.
The numbers of Lactobacillus spp. at the end of storage decreased in the order, CO2 > N2 > vacuum. Lactobacillus viridescens generally constituted a substantial part of the Lactobacillus flora (5–72%). On the sausages two large uniform groups of unidentifiable homofermentative Lactobacillus spp. were also found. 相似文献
The predominant organisms on the fresh products were Bacillus spp., coryneform bacteria, Flavobacterium spp. and Pseudomonas spp.
At the end of the storage time the microflora on both products in the three gas atmospheres, consisted mainly of Lactobacillus spp. and two large groups of organisms that could not be identified as any described genus. Some of the unidentified strains could be classified as a Lactobacillus sp. after subsequent subculturing on laboratory media.
The numbers of Lactobacillus spp. at the end of storage decreased in the order, CO
19.
Abstract Denitrification rates were measured as N2 O production in two water-logged forest soils at monthly intervals. The effect of acetylene inhibition and the addition of nitrate, glucose, acetate and celloboise in field incubations was examined.
N2 O release from the two soils was very low, 26 mg N2 m−2 y−1 in ash and 178 mg N2 in alder. In acetylene inhibited incubations N2 O production was higher, 296 and 486 mg N2 m−2 y−1 in ash and alder respectively. After addition of nitrate and C-sources to a 10 mM concentration, denitrification rates increased to 5–15 times higher values.
The denitrification rates below 4°C were low and most N2 O was produced in late spring and summer.
The highest rate of denitrification during a 50 h incubation experiment occurred between 3 and 23 h. 相似文献
N
The denitrification rates below 4°C were low and most N
The highest rate of denitrification during a 50 h incubation experiment occurred between 3 and 23 h. 相似文献
20.
Abstract: A continuous dual 13 CO2 and 15 NH4 15 NO3 labelling experiment was undertaken to determine the effects of ambient (350μmol mol-1 ) or elevated (700μmol mol-1 ) atmospheric CO2 concentrations on C and N uptake and allocation within 3-year-old beech ( Fagus sylvatica L.) during leafing. After six weeks of growth, total carbon uptake was increased by 63 % (calculated on total C content) under elevated CO2 but the carbon partitioning was not altered. 56 % of the new carbon was found in the leaves. On a dry weight basis was the content of structural biomass in leaves 10 % lower and the lignin content remained unaffected under elevated as compared to ambient [CO2 ]. Under ambient [CO2 ] 37 %, and under elevated [CO2 ] 51 %, of the lignin C of the leaves derived from new assimilates. For both treatments, internal N pools provided more than 90 % of the nitrogen used for leaf-growth and the partitioning of nitrogen was not altered under elevated [CO2 ]. The C/N ratio was unaffected by elevated [CO2 ] at the whole plant level, but the C/N ratio of the new C and N uptake was increased by 32 % under elevated [CO2 ]. 相似文献