Microbial removal of nitrogen monoxide (NO) under aerobic conditions

Nitrogen oxide gas (NO_x), consisting of nitrogen monoxide (NO) and nitrogen dioxide (NO₂), at a low concentration corresponding to that on roads as a result of exhaust from automobiles, was supplied for 25 days through a laboratory-scale biofilter packed with soil as a packing material. The removal efficiency of NO₂ by soil was almost 100%, and the removal efficiency of NO was 60% on average and 86% at maximum. By using -irradiated soil as a packing material, NO₂ was completely removed mainly by adsorption onto or absorption into the packing material. However, the removal efficiency of NO in the sterilized soil was only 20%, suggesting that NO in soil was removed microbiologically under aerobic conditions.     

Influences of Lead (II) Chloride on the Nitrogen Metabolism of Spinach

Lead (Pb²⁺) is a well-known highly toxic element. The mechanisms of the Pb²⁺ toxicity are not well understood for nitrogen metabolism of higher plants. In this paper, we studied the effects of various concentrations of PbCl₂ on the nitrogen metabolism of growing spinach. The experimental results showed that Pb²⁺ treatments significantly decreased the nitrate nitrogen absorption and inhibited the activities of nitrate reductase, glutamate dehydrogenase, glutamine synthase, and glutamic–pyruvic transaminase of spinach, and inhibited the synthesis of organic nitrogen compounds such as protein and chlorophyll. However, Pb²⁺ treatments increased the accumulation of ammonium nitrogen in spinach cell. It implied that Pb²⁺ could inhibit inorganic nitrogen to be translated into organic nitrogen in spinach, thus led to the reduction in spinach growth.     

Morphology and taxonomy of Oscillatoria redekei (Cyanophyta)

The polymorphous trichome apices of Oscillatoria redekei are described with respect to their shape and size. Breakage of trichomes may occur either trans- or intercellularly. The development and localization of intercellular trichome breakage were observed. Transmission electron microscopy shows that the fine structure of cell walls resembles that of Pseudanabaena galeata. Longitudinal walls consist of three or four layers and lack a sheath, while the cross walls are composed of three layers with a dominating L₂-layer. In contrast to P. galeata, the centroplasm and most of the thylakoidal region of adjacent cells of O. redekei are connected by the cross walls forming obtuse angles at the site of the longitudinal walls. The main characteristics of O. redekei and of Pseudanabaena species are discussed.     

Syntheses and characterization of the W(II) and W(III) N2 complexes, [WCl2(PMe3)3]2N2 and [WCl3(PMe3)2]2N2

Refluxing WCl₄(PMe₃)₃ under a nitrogen atmosphere in the presence of two equivalents of sodium amalgam leads to a reduction to the W(II) complex [cis,mer-WCl₂(PMe₃)₃]₂N₂ (1), which can be converted to [mer,trans-WCl₃(PMe₃)₂]₂N₂ (2) via appropriate oxidation/chlorination. Structural data have been obtained for both complexes, and demonstrate significantly increased steric crowding in 1 due to PMe₃/PMe₃ interactions. The N-N bond distances in the two compounds are similar, at 1.279(4) and 1.243(18) Å, respectively.     

模拟氮沉降对杉木幼苗细根化学计量学特征的影响

为了揭示全球氮(N)沉降对杉木人工林细根碳(C)、N、磷(P)元素组成的影响,在福建三明陈大国有林场开展杉木(Cunninghamia lanceolata)幼苗模拟N沉降试验,设置了对照(CK)、低N(LN,40 kg N hm~(-2)a~(-1))、高N(HN,80 kg N hm~(-2)a~(-1))3个处理,每个处理5个重复。采用内生长环法通过2年4次取样探讨N沉降对细根C、N、P化学计量学的影响。结果显示:(1) N添加在2015年降低细根C浓度,此后低N处理无影响,高N添加在2016年增加了细根C浓度;高N添加提高了细根(特别是0—1 mm细根) N浓度,但低N添加则无显著影响,甚至在2016年7月显著降低细根N浓度; N添加在2015年对细根P浓度无显著影响,但在2016年导致细根(特别是0—1 mm细根) P浓度降低。(2)低N添加在2016年显著提高细根的C∶N比,而高N添加则在2015年1月显著降低细根的C∶N比;低N添加对细根N∶P比没有显著影响,而高N添加则在大部分取样时间里显著增加了细根N∶P比。(3)不同处理细根C浓度、C∶N比均随着时间的增加呈增加趋势,而细根N浓度和N∶P比呈降低趋势。本研究表明,N添加对杉木细根化学计量学特征的影响因不同N添加水平而异,并受苗木生长的稀释效应所调节。     

Effects of western juniper (Juniperus occidentalis) control on ecosystem nitrogen stocks in central Oregon,USA

控制西美圆柏数量对美国俄勒冈州中部生态系统氮储量的影响 在美国俄勒冈州,控制西美圆柏(Juniperus occidentalis)的数量是一种公认的牧场管理措施,该做法 有助于恢复蒿草草原(sagebrush steppe)生境,该生境对野生动物和家畜都十分重要。然而,尽管控制木本 植物数量会对当地的流域管理和区域性氮库造成重要影响,但砍伐西美圆柏对生态系统中氮元素的影响问题尚未得到很好的解决。本文定量研究了两个相邻流域生态系统中的氮储量,其中一个流域经过处理(流域内的大部分圆柏已被清除掉),而另一个流域未处理(圆柏未被清除)。在圆柏被移除13年后,我们测定了两个流域里圆柏树林、灌木丛、草丛和枯枝落叶层的地上氮储量,以及两个流域中两个土层(0–25和25–50 cm)内的地下氮储量(根系和土壤氮储量)。研究结果表明,未处理流域的地上氮储量是处理流域 的6.9倍,因为未处理流域的地上生物量要大得多。然而,由于砍伐圆柏导致林下植被的根系生物量增加,所以处理流域的根系氮储量是未处理流域的3.1倍。0–25和25–50 cm土层氮储量没有受到圆柏砍伐的影响。总体而言,生态系统总氮储量在处理流域(9536 kg N ha⁻¹)和未处理流域(9456 kg N ha⁻¹)之间并没有显著差异。在两个流域里,生态系统中最大的氮积累量(至少95%的生态系统总氮量)均存在于地下(0–25 cm深的土壤以及根系)。这项研究证明,清除圆柏并不会显著影响生态系统的储氮能力。     

The importance of avian-contributed nitrogen (N) and phosphorus (P) to Lake Grand-Lieu,France

The largest natural lake in France, Grand-Lieu, has suffered eutrophication. The objective of the study was to estimate the annual input of nutrients (N, P) resulting from avian excrement, deposited by birds feeding out of the lake and returning to its waters for breeding or roosting, as compared to the input by the rivers that enter in the lake. Two years are compared: 1981–82 and 1990–91. About 1600–2000 breeding herons and cormorants, 20 000–33 000 wintering ducks, gulls and cormorants and 1–2.4 million starlings deposited about 5800 kg total N in 1981–82 and 7640 kg in 1990–91. Respectively, 2000 and 2530 kg total P were deposited over the same time periods. These represent 0.7% and 0.4% of the total N input of the lake and 2.4 and 6.6% of the total P input in 1981–82 and 1990–91. Starlings account for 74% of the N and mallards most of the rest. P input by starlings (36% in 1981–82, 41% in 1990–91), and by mallards and herons (35% and 27% in 1981–82 and 22% and 24% in 1990–91 respectively) plays an appreciable role among birds. During the plant growing period (April–September), the contribution by birds can increase to 37% of total P input of the lake. Piscivorous bird colonies concentrate Phosphorus 42 times more within the colony than outside the colony. Overall, the role birds play in total N and P input is relatively small due to very high inputs from human sewage and agriculture run off. The monthly mean concentration of the water of the two rivers reaches currently 10 mg l^–1 of N (to 23 mg during peak floods) and 394 mg m^–3 of P (to 468 mg during peak floods). Earlier, for example in the 1960's, water in Brittany only contained 0.1 to 1.1 mg 1^–1 of N and 1 to 5 mg m^–3 of P during the maximum flow period. At this time, birds could probably have represented annually up to 37% of the N input and up to 95% of the P input to the lake.     

Nitrogen partitioning and blood meal utilization by Aedes aegypti (Diptera Culicidae)

The utilization of the blood meal by mosquitoes was investigated by first feeding females quantities of blood ranging from 1 to 5 mg, and then analyzing the faeces for the various by-products of protein catabolism that were subsequently eliminated. The nitrogeneous waste products in order of importance were uric acid, histidine, ammonia and arginine. Only traces of the other amino acids were excreted.The total amount of each faecal substance varied linearly with the quantity of blood ingested, however their relative proportions did not change. Regardless of blood meal size the quantily of uric acid and ammonia produced indicates that about 80% of the non-histidine and arginine amino acids are deaminated and utilized for metabolic purposes other than egg protein synthesis.Most of the histidine and about one half of the arginine content of the blood were excreted as free amino acids, but the other amino acids were lost in trace amounts.Nineteen per cent of the total ingested amino acids was incorporated into soluble yolk proteins and this proportion was constant even for small blood meals that result in a reduction in the numbers of eggs produced.The comparative aspects of nitrogen partitioning and blood meal utilization by haematophagous insects, as well as the factors that affect blood meal utilization and fecundity in A. aegypti are discussed.     

Interaction between atmospheric and pedospheric nitrogen nutrition in spruce (Picea abies L. Karst) seedlings

The effect of NO₂ fumigation on root N uptake and metabolism was investigated in 3-month-old spruce (Picea abics L. Karst) seedlings. In a first experiment, the contribution of NO₂ to the plant N budget was measured during a 48 h fumigation with 100mm³m^?3 NO₂. Plants were pre-treated with various nutrient solutions containing NO₂ and NH₄⁺, NO₃^? only or no nitrogen source for 1 week prior to the beginning of fumigation. Absence of NH₄⁺ in the solution for 6d led to an increased capacity for NO₃^? uptake, whereas the absence of both ions caused a decrease in the plant N concentration, with no change in NO₃^? uptake. In fumigated plants, NO₂ uptake accounted for 20–40% of NO₃^? uptake. Root NO₃^? uptake in plants supplied with NH₄⁺plus NO₃^? solutions was decreased by NO₂ fumigation, whereas it was not significantly altered in the other treatments. In a second experiment, spruce seedlings were grown on a solution containing both NO₂ and NH₄⁺ and were fumigated or not with 100mm³m^?3 NO₂ for 7 weeks. Fumigated plants accumulated less dry matter, especially in the roots. Fluxes of the two N species were estimated from their accumulations in shoots and roots, xylem exudate analysis and ¹⁵N labelling. Root NH₄⁺ uptake was approximately three times higher than NO₃^? uptake. Nitrogen dioxide uptake represented 10–15% of the total N budget of the plants. In control plants, N assimilation occurred mainly in the roots and organic nitrogen was the main form of N transported to the shoot. Phloem transport of organic nitrogen accounted for 17% of its xylem transport. In fumigated plants, neither NO₃^? nor NH₄⁺ accumulated in the shoot, showing that all the absorbed NO₂ was assimilated. Root NO₃^? reduction was reduced whereas organic nitrogen transport in the phloem increased by a factor of 3 in NO₂-fimugated as compared with control plants. The significance of the results for the regulation of whole-plant N utilization is discussed.     

NITROGEN LIMITATION EFFECTS OF DIFFERENT NITROGEN SOURCES ON NUTRITIONAL QUALITY OF TWO FRESHWATER ORGANISMS, SCENEDESMUS QUADRICAUDA (CHLOROPHYCEAE) AND SYNECHOCOCCUS SP. (CYANOPHYCEAE)

Food quality for grazers has been related to mineral (nitrogen, phosphorus) and biochemical (amino acids, fatty acids) constituents. The aim of the study was to examine the influence of different nitrogen sources on these constituents in two organisms, the green alga Scenedesmus quadricauda Turp. and the cyanobacterium Synechococcus sp., commonly used in feeding experiments. The two organisms were grown in continuous cultures at different growth rates. Nitrate or ammonium salts were used as nitrogen sources under both replete and limited conditions. Carbon content (mg·g⁻¹ dry weight) was stable in both organisms independent of nitrogen source, nitrogen limitation, and growth rate. Nitrogen content decreased with limitation and growth rate in Scenedesmus and to a lesser degree in Synechococcus , whereas changes in phosphorus content were not statistically significant. The relative proportions of amino acids (% of total amino acids) were relatively stable in both organisms, whereas the proportions of fatty acids varied with growth rate and limitation. Fatty acid content was much lower in Synechococcus than in Scenedesmus . At N limitation, polyunsaturated fatty acids (PUFAs) showed lower levels in both organisms. The change occurred in the ω3 PUFA (linolenic acid) of the green alga and in the ω6 PUFA (linoleic acid) of the cyanobacterium. The difference in the response of N limitation in the two organisms may be traced to the different composition of the chloroplast membranes (the prokaryotic way) and the microsomal membranes (the eukaryotic way) where the desaturation takes place.     

Ammonia oxidation (amoA) and nitrogen fixation (nifH) genes along metasandstone and limestone caves of Brazil

Abstract

Many cave-dwelling microorganisms have been studied, but little is known about whether genes related to the nitrogen cycle are present in this environment, particularly in sandstone caves. The profiles of nitrogen fixation (nifH) and archaeal and bacterial ammonia oxidation (amoA) genes were analyzed along a cave of metasandstone and limestone lithologies. Using polymerase chain reaction (PCR)-denaturing gradient gel electrophoresis and quantitative PCR to evaluate these genes, we analyzed the variations in the microorganisms and frequency of these genes along the caves. In both caves analyzed for nifH, different community profiles were observed, particularly in entrance samples. Quantitative PCR of the genes showed that samples from the entrance of the caves contained a larger number of copies of amoA. In addition, archaeal amoA was predominant compared to bacterial amoA. The present study demonstrated that the genes for nitrogen fixation and ammonia oxidation are present in both cave lithologies and that their frequency and the organisms present along the caves vary with factors such as the characteristics of the cave itself.     

模拟氮沉降对温带阔叶红松林地土壤氮素净矿化的影响

以长白山阔叶红松混交林为研究对象,于2006—2008年原位模拟不同形态氮((NH4)2SO4、NH4Cl和KNO3)沉降水平(22.5和45kgN·hm-2·a-1),利用树脂芯法技术(resin-core incubation technique)测定了表层(有机层0～7cm)和土层(0～15cm)土壤氮素净矿化、净氨化和净硝化通量的季节和年际变化规律。同时,结合前人报道的有关林地碳、氮过程及其环境变化影响的结果,力求有效预估森林生态系统中氮素年矿化通量对大气氮沉降量和水热条件等因子变化的响应。结果表明,长白山阔叶红松林地土壤氮素年净矿化通量为1.2～19.8kgN·hm-2·a-1,2008年不同深度的土壤氮素年净矿化通量均显著高于2006和2007年(P<0.05)。随着模拟氮沉降量增加,土壤氮素净矿化通量也随之增加,尤其外源NH4+-N输入对净矿化通量的促进作用更为明显(P<0.05),但随着施肥年限的延长,这种促进作用逐渐减弱。与林地0～15cm土壤相比,氮沉降增加对0～7cm有机层氮素净氨化和净矿化通量的促进作用更为明显,尤其NH4Cl处理的促进作用更大。结合前人报道的野外原位观测结果,土壤氮素年净矿化通量随氮素沉降量的增加而增大,氮沉降量对不同区域森林土壤氮素净矿化通量的贡献率约为52%;氮沉降量(x1)和pH值(x2)可以解释区域森林土壤氮素年净矿化通量(y)变化的70%(y=0.54x1-18.38x2-109.55,R2=0.70,P<0.0001)。前人研究结果仅提供区域年均温度,未考虑积温的影响,这可能是造成年净矿化通量与温度无关的原因。今后的研究工作应该加强区域森林土壤积温观测,进而更加准确地预估森林土壤氮素的年净矿化通量。     

微生物厌氧氨氧化耦合铁还原的研究进展及展望

厌氧氨氧化耦合铁还原[ammonium oxidation coupled to Fe(Ⅲ) reduction, Feammox]作为一种连接氮循环和铁循环之间的氮代谢途径,在自然界中氨氮转化过程中起到了重要作用。系统研究Feammox驱动的氮铁的生物地球化学耦合过程及其受控因素,有助于深入理解地球元素循环的微生物机制,也有助于揭示Feammox在缺氧地质历史时期对古海洋氮库演变和含铁矿物形成过程中的作用。本文从Feammox发展历史、相关微生物、影响因素和潜在地质意义等方面综述了Feammox的研究过程和研究内容,并对Feammox的未来研究方向提出展望。     

CONSUMPTION OF ULVA LACTUCA (CHLOROPHYTA) BY THE OMNIVOROUS MUD SNAIL ILYANASSA OBSOLETA (SAY)

Marine invertebrate grazing on temperate macroalgae may exert a significant “top-down” control on macroalgal biomass. We conducted two laboratory experiments to test (1) if consumption by the omnivorous mud snail Ilyanassa obsoleta (Say) on the macroalga Ulva lactuca Linnaeus was a function of food quality (nitrogen content) and (2) if grazing on benthic macroalgae occurred at significant rates in the presence of alternative food sources in the sediment (detritus, larvae, benthic microalgae). Grazing rates were higher for N-enriched macroalgae; however, all snails lost weight when grazing on macroalgae alone, indicating that U. lactuca was a poor food source. The presence of sediment from two sites, a sandy lagoon and an adjacent organic-rich muddy tidal creek, did not affect consumption of macroalgae in microcosm experiments, and the grazing snails were capable of significantly reducing macroalgal biomass associated with both sediment types. Grazing rates by this omnivore were as high as 10.83 mg wet weight·individuals ^{− 1}·d ^{− 1} and were similar to those recorded for herbivorous species. In situ loss rates calculated from average grazing rates per individual and snail abundances (up to 3.5 g dry weight·m ^{− 2}·d ^{− 1}) also were comparable with those calculated for herbivorous species. This level of grazing could remove up to 88% of new macroalgal growth at the lagoon site where the N supply was relatively low but had a much smaller effect (18% of new growth) at the high-nutrient creek site. Snails facilitated macroalgal growth at both sites by increasing tissue N content by 40%–80%. Consumption and digestion of macroalgae aided in the recycling of nutrients temporarily bound in the algae and resulted in enrichment of surficial sediments. Increased N sequestration in the sediments also was associated with an interruption of snail burrowing behavior due to persistent anoxia in sediments rich in decaying algal material. Our data suggest that in shallow lagoons where mud snails and benthic macroalgae coexist, grazing may influence N retention in macroalgal biomass.     

INTERACTIONS BETWEEN NITRATE UPTAKE AND NITROGEN FIXATION IN CONTINUOUS CULTURES OF THE MARINE DIAZOTROPH TRICHODESMIUM (CYANOBACTERIA)1

Diazotrophic cyanobacteria can take up combined nitrogen (nitrate, ammonium, amino acids, dissolved organic nitrogen) from solution, but the interaction between N₂ fixation and uptake of combined nitrogen is not well understood. We studied the effects of combined nitrogen ) additions on N₂ fixation rates in the cyanobacterium Trichodesmium erythraeum (IMS‐101) maintained in continuous culture in an N‐free medium (YBCII) and a 12:12‐h light:dark cycle. We measured acetylene reduction rates, nutrient concentrations, and biomass throughout the 12 h of illumination after the addition of nitrate (0.5–20 μM) at the start of the light period. Compared with unamended controls, Trichodesmium showed strong inhibition of acetylene reduction (up to 70%) in the presence of , with apparent saturation of the inhibition effect at an initial concentration of approximately 10 μM. The inhibition of acetylene reduction persisted through much of the light period as concentration in the culture vessel decreased. Recovery of N₂ fixation was observed late in the light period in cultures amended with low concentrations of (<5 μM) when ambient concentrations had decreased to 0.3–0.4 μM in the culture vessel. Nitrate uptake accounted for as much as 86% of total N uptake and, at the higher treatment concentrations, more than made up for the observed decrease in N₂ fixation rates. We conclude that Trichodesmium can obtain significant quantities of N through uptake of nitrate and does so in preference to N₂ fixation when sufficient is available.     

Coordination modes of the novel bifunctional nitrogen ligands 8-(2-pyridyl)quinoline and 8-(6-methyl-2-pyridyl)quinoline towards palladium and platinum. X-ray crystal structures of (8-(2-pyridyl)quinoline)Pd(Me)Cl, (8-(2-pyridyl)quinoline)-Pd(C(O)Me)Cl and (8-(2-pyridyl)quinoline)Pd(PEt3)Cl2

The coordination chemistry of the new bidentate nitrogen ligands 8-(2-pyridyl)quinoline (8-PQ) and 8-(6-methyl-2-pyridyl)quinoline (Me-8-PQ) towards palladium and platinum has been studied. Several (NN)Pd(R)Cl and (NN)Pd(alkene) complexes have been synthesized. The complex (8-PQ)Pd(Me)Cl has been characterised by a single crystal X-ray determination (crystal data triclinic space group

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). A fast CO insertion occurs into the palladium-carbon bond of the complexes (NN)Pd(Me)Cl providing the (NN)Pd(C(O)Me)Cl complexes. For (8-PQ)Pd(C(O)Me)Cl an X-ray structure determination has been carried out (crystal data: monoclinic space group P2₁/c with a=9.084(4), B=10.179(3), C=16.400(3) Å, β=95.59(2)°, V=1509.2(9) ų, R=0.043, Z=4). Unexpected in both molecular structures is the large dihedral angle between the plane of the bidentate nitrogen ligand and the coordination plane of the palladium. Both bidentate coordinating ligands 8-PQ and Me-8-PQ show a relatively large bite angle. A monodentate coordination mode has been observed for the complexes (NN)M(PEt₃)Cl₂ (M=Pd, Pt), as the pyridyl group of the ligand is coordinated to the metal while the quinoline group is dissociated from the metal, which is shown in the X-ray structure determination for the complex (8-PQ)Pd(PEt₃)Cl₂ (crystal data: monoclinic space group P2₁/a with A=15.736(2), B=7.782(1), C=18.255(3) Å, β=102.98(1)°, V=2178.3(6) ų, R=0.062, Z=4).     

Integrated tank cultivation of salmonids and Gracilaria chilensis (Gracilariales,Rhodophyta)

In order to study the N and P balances in the Driss I reservoir, we measured concentrations in the water of these elements, their sedimentation rates, and their input by the river Inaouen and output through the dam. Supply and loss of N and P were calculated from samples collected every 48 hours and were for N 15 and 27. 5 mg m⁻² d⁻¹ and for P 33.6 and 1.1 mg m⁻² d⁻¹ respectively. The sedimentation rates, determined using sediment traps, were high, about 75 mg m⁻² d⁻¹ for N and 34 mg m⁻² d⁻¹ for P. Phosphate input came from point sources and was mainly in particulate form. A large fraction of the phosphate sedimented in the form of calcium bound phosphate, with some iron bound phosphate. Bioavailability was, however, low, as the particulate phosphate disappeared rapidly from the epilimnion because of the high sedimentation rate. The ratio Tot-N/Tot-P of the sedimented particulate matter varied between 0.05 and 7.74 and depended on primary production and watergate management.     

Calanoida (Copepoda) species composition changes in the reservoirs of São Paulo State (Brazil) in the last twenty years

A sampling programme was undertaken to monitor the total carbon (C) and total nitrogen (N) content of suspended matter in a small undisturbed upland drainage basin in the New Territories of Hong Kong. Mean C and N contents were 12.9% and 1.0%, respectively, for 132 samples. Samples collected under stable flow conditions had mean C and N contents of 12.8% and 1.1%, respectively. Stormflow samples had mean C and N values of 12.9% and 1.0%, respectively, which were very similar to the levels observed under stable flow conditions. The mean C: N ratios of 12.5 and 13.4 for stable flow and stormflow also reveal little variation with hydrologic conditions. When all the data is considered, little seasonal variation was observed in C and N. However, in winter there is a significant difference in C and N content between stable and stormflow samples. When C and N are plotted against water level, the scattergraphs suggest that as stage increases the percentage of C and N in the suspended matter declines. Scattergraphs of C and N against suspended sediment concentration reveal a negative association. This may reflect the dominance of inorganic sediments produced by erosion processes during rainfall.