固氮施氏假单胞菌(Pseudomonas stutzeri)A1501同化硝酸盐代谢基因簇分布及调控研究

固氮施氏假单胞菌(Pseudomonas stutzeri)A1501在有氧条件下能够利用硝酸盐/亚硝酸盐为唯一氮源生长,表明该菌除了具有固氮和反硝化等氮循环系统外还有同化硝酸盐/亚硝酸盐系统.为进一步阐明该菌同化硝酸盐的代谢机制,利用生物信息学手段分析了硝酸盐同化相关基因的组成及分布情况,并初步研究了同化硝酸盐途径特...     

Reducing phosphorylation of nitrate reductase improves nitrate assimilation in rice

Nitrate reductase(NR) is an important enzyme for nitrate assimilation in plants, and post-translational phosphorylation regulates NR activity. To evaluate the impact of the dephosphorylation of nitrate reductase 1(NIA1) protein on NR activity,nitrogen metabolism and plant growth, NIA1 phosphorylation site directed mutant lines(S532 D and S532 A) and an OsNia1 over-expression line(OE) were constructed, and the phenotype, NIA1 protein and its phosphorylation level, NR activity,nitrate metabolism a...     

Inorganic nitrogen removal from wastewater: effect on phytoplankton growth in coastal marine waters

Algal bioassays were used to demonstrate the high efficiency of a comnbined tertiary wastewater treatment and marine aquaculture system in removing inorganic nitrogen, and to show that the coastal waters off Woods Hole, Massachusetts, are limited in nitrogen for marine phytoplankton growth. When nutrients were removed from secondarily treated domestic wastewater through assimilation by phytoplankton in an outdoor growth pond, the pond effluent, in varying dilutions with seawater, could not support more phytoplankton growth than the seawater alone. However, when nitrogen was added back to the mixtures of pond effluent and seawater, the phytoplankton growth response was similar to that with a mixture of wastewater and seawater. This is similar to the findings of other researchers, and suggests that nitrogen may be the key growth-limiting nutrient in many coastal marine waters. The combined tertiary treatment-marine aquaculture system appears to be an effective means of removing nitrogen from secondarily treated wastewater and controlling eutrophication of coastal marine waters.     

植物内生菌促进宿主氮吸收与代谢研究进展

内生菌与植物共生能够提高宿主的氮吸收与氮代谢水平,这可能是由于内生菌在植物体内引发的多种效应的综合结果.植物内生菌能够通过促进植物根系发育和固氮作用为宿主植物提供更多的无机氮素;能够通过分泌多种胞外酶系如漆酶、蛋白水解酶等使宿主植物更好地利用有机氮素;能够提高宿主氮代谢关键酶如硝酸还原酶(NR)、谷氨酰胺合成酶(GS)等酶的活性;能够提高宿主植物激素水平和维生素含量从而促进宿主氮代谢;能够通过影响宿主植物氮代谢促进宿主植物分蘖、提高宿主植物叶绿素含量和光合速率等等.综述了国内外关于植物内生菌促进宿主氮代谢的相关报道,归纳了植物内生菌影响宿主氮素吸收与代谢的可能机制,并展望了关于植物内生菌促进宿主氮代谢机制方面的研究方向.     

氮素调控对玉米氮素同化过程及产量的影响

氮素调控措施与作物氮素吸收利用和产量密切相关,但目前关于不同氮素调控措施对玉米主要生育期氮素同化过程的影响仍不清楚。以郑单958为试验材料,设置不施氮肥（CK）、传统施肥（CN）、氮肥+生物炭（SN）和氮肥+硝化抑制剂DMPP（DN）4个处理,分析不同氮素调控对玉米氮素同化过程中铵态氮和硝态氮含量、硝酸还原酶（NR）和谷氨酰胺合成酶（GS）活性、游离氨基酸和可溶性蛋白含量以及氮素利用率和产量的影响。结果表明：DN和SN处理较传统施肥处理均可以提高玉米植株体内硝态氮和铵态氮含量、NR和GS活性;DN和SN处理显著提高灌浆期谷氨酸、游离氨基酸和可溶性蛋白含量;DN处理成熟期籽粒的氮素积累量显著高于SN和CN处理,分别显著增加18.4%和30.0%;DN处理产量最高,SN次之,二者并无显著差异,但相较CN处理分别显著增产1 483.0和1 154.2 kg·hm^-2。两种氮素调控均促进了玉米对氮素的吸收,显著提高氮肥吸收利用率,其中硝化抑制剂处理氮肥吸收利用率最高且显著高于其他处理。综上,生物炭或硝化抑制剂配施氮肥,可以促进玉米氮素同化和转运过程,显著提高玉米产量和氮肥利用效率,综合产量、籽粒氮素积累量和氮肥吸收利用率,硝化抑制剂配施氮肥可作为淮河流域玉米高产高效的栽培措施。     

Nitrogen fixation by a blue-green epiphyte on pelagic sargassum

Nitrogen fixation by Dichothrix fucicola, an epiphyte on pelagic Sargassum, was measured in May and June 1972 in the western Sargasso Sea and the Gulf Stream. This is the first report of nitrogen fixation by a heterocyst-bearing blue-green alga in the open ocean, and also the first observation of nitrogen fixation in the genus Dichothrix. Cellular carbon/nitrogen ratios suggested that the Dichothrix was nitrogen-starved. In dense aggregations of Sargassum, such as rafts or windrows, the enrichment of surface seawater with combined nitrogen from nitrogen fixation may be pronounced.     

水稻增硝营养的生理与分子生物学机制

 前人对水稻氮（N）营养的研究主要侧重在铵（NH4+）营养而忽略了对硝（NO3－）营养的研究。但值得注意的是,水稻根系能分泌氧气（O2）,这些O2能被硝化微生物利用,从而将NH4+氧化成NO3－。因此,即便是完全淹水,水稻根系也是处于铵、硝混合营养中。本文首先论述了水稻根际的硝化作用及增硝营养的可行性,然后提出增硝营养可促进水稻根系生长、氮素吸收和同化,并阐述了目前增硝营养条件下硝酸盐转运蛋白、铵转运蛋白和基因芯片的分子生物学研究进展,并提出水稻对增硝营养的响应度强弱可能是水稻品种氮素效率差异性的因子之一,最后提出了今后在水稻增硝营养方面的研究方向。     

水稻T-DNA插入氮营养缺陷型突变体的氮营养特征

利用营养液培养试验,研究水稻T-DNA插入氮营养缺陷型突变体的氮营养特性.结果表明,氮营养缺陷型突变体突变植株硝态氮和铵态氮吸收速率均低于原始亲本,植株氮含量及硝酸还原酶活性降低,氮同化能力下降,根系变短,根系体积及根系活跃面积变小,植株变矮.     

低磷胁迫对水曲柳幼苗光合速率与氮素同化的影响

在温室内采用盆栽砂培的方法,对不同供磷水平(0.125、0.250、0.500和1.000mmol/L)的水曲柳幼苗进行了光合速率与氮素同化的研究。结果表明,水曲柳幼苗最大净光合速率随供磷减少而降低,供磷水平最低(0.125mmol/L)时水曲柳幼苗叶片最大净光合速率为正常供磷(1mmol/L)的61%,而低磷水平处理(0.125、0.250、0.500mmol/L)时的光补偿点均高于正常供磷处理。各供磷水平下,叶片中的全氮、硝态氮和铵态氮含量均高于根系。随供磷的减少,叶片与根系中硝态氮含量均降低,同时,低磷水平处理(0.125、0.250、0.500mmol/L)时根系铵态氮含量均高于正常供磷(1mmol/L),表明低磷胁迫下水曲柳偏向铵态氮的吸收。但是,叶片全氮含量随供磷水平的降低而下降。供磷水平较低时(0.125和0.25mmol/L)叶片硝酸还原酶(NR)活性低于根系,而在供磷水平较高时(0. 5和1mmol/L)则相反。随供磷的减少,叶片和根系NR活性,以及叶片天冬氨酸转氨酶(AAT)活性均逐渐降低,而叶片谷氨酰胺合成酶(GS)活性变化较小。上述结果表明,在低磷胁迫下水曲柳幼苗氮素吸收数量和同化酶活性均降低,减少了氮素向叶片的分配,导致植株光合速率下降。      

遮光下外源水杨酸对韭菜硝酸盐还原同化效应的研究

【目的】通过研究不同光强下外源水杨酸（SA）对韭菜叶片硝酸盐（NO3-）累积、氮代谢关键酶活性、光系统II电子传递速率（ETR）及主要氨基酸和可溶性蛋白合成的调控效应,以期明确遮光水平下SA对硝酸盐还原同化的影响。【方法】以韭菜品种‘新世纪雪韭’为供试材料,在前期试验工作基础上,采用显著降低韭菜硝酸盐累积的3.0 mmol•L-1 SA对韭菜叶面进行喷施处理,设自然光（900-1 050 μmol•m-2•s-1）和遮光（40%自然光）2种光照强度,分析SA对韭菜硝酸盐累积及NO3-还原同化的影响。【结果】SA处理缓解了遮光水平下韭菜叶片氮代谢关键酶硝酸还原酶（NR）、谷氨酰胺合成酶（GS）、谷氨酸草酰乙酸转氨酶(GOT)和谷氨酸丙酮酸转氨酶（GPT）活性的降低,显著降低了硝酸盐的累积,其中,与弱光对照相比,SA处理下GOT活性和GPT增幅较明显,分别为23.7%和12.3%;SA处理还显著提高了弱光下叶片的全氮含量和干物率,但叶绿素含量和光系统间电子传递速率ETR的增幅不大;另外,SA处理增加了弱光下韭菜叶片多数游离氨基酸组分的含量,效果最为显著的为色氨酸和丝氨酸,分别比对照提高了89.8%和50.6%;并且提高了游离氨基酸总量和可溶性蛋白含量,但降低了游离氨基酸与可溶性蛋白比值A/P。【结论】弱光降低了韭菜氮素同化能力和物质生产能力,而SA处理促进了弱光下韭菜叶片氮代谢中硝酸盐的还原和铵的同化,同时调动转氨作用的积极协同配合,促进了硝态氮转化为游离氨基酸和可溶性蛋白,这可能是遮光下SA降低韭菜硝酸盐累积的一个重要原因。     

Major role of the cyanobacterium trichodesmium in nutrient cycling in the north atlantic ocean

The diazotrophic cyanobacterium Trichodesmium is a large (about 0.5 by 3 millimeters) phytoplankter that is common in tropical open-ocean waters. Measurements of abundance, plus a review of earlier observations, indicate that it, rather than the picophytoplankton, is the most important primary producer (about 165 milligrams of carbon per square meter per day) in the tropical North Atlantic Ocean. Furthermore, nitrogen fixation by Trichodesmium introduces the largest fraction of new nitrogen to the euphotic zone, approximately 30 milligrams of nitrogen per square meter per day, a value exceeding the estimated flux of nitrate across the thermocline. Inclusion of this organism, plus the abundant diazotrophic endosymbiont Richelia intracellularis that is present in some large diatoms, in biogeochemical studies of carbon and nitrogen may help explain the disparity between various methods of measuring productivity in the oligotrophic ocean. Carbon and nitrogen fixation by these large phytoplankters also introduces a new paradigm in the biogeochemistry of these elements in the sea.     

The removal of nitrate reductase phosphorylation enhances tolerance to ammonium nitrogen deficiency in rice

Nitrate reductase(NR) is a key enzyme for nitrogen assimilation in plants, and its activity is regulated by posttranslational phosphorylation. To investigate the effects of dephosphorylation of the NIA1 protein on the growth and the physiological and biochemical characteristics of rice under different forms of nitrogen supplies, the phenotypes, nitrogen metabolism and reactive oxygen metabolism were measured in NIA1 phosphorylation site-directed mutant lines(S532 D and S532 A), an Os Nia1 over-e...     

Evaluation of the Role of Mixed Amino Acids in Nitrate Uptake and Assimilation in Leafy Radish by Using 15N-Labeled Nitrate

In this paper, the role of mixed amino acids in nitrate uptake and assimilation was evaluated in leafy radish by using ^15N labeled nitrate. The mixtures of alanine, β-alanine, aspartic acid, asparagines, glutamic acid, glutamine, and glycine were sprayed to plant leaf two or four times. The activity of the enzymes related to the process of NO3- reduction （nitrate reductase, nitrite reductase and glutamine synthetase） was affected differently depending on the application rate of mixed amino acids. Applying mixed amino acids increased the fresh weight, dry weight, and N yield. The NO3 content was reduced to 24-38%, but no significant differences were observed in amino acids and proteins. In addition, the nitrogen derived from fertilizer and the ^15N-NO3-recovery rate increased to 2-8% and 15-47%, respectively. These results strongly suggest that the positive effect of mixed amino acids on nitrate uptake and assimilation might be attributed to the regulation on NO3- uptake and assimilation, but not to the preference for amino acids as sources of reduced nitrogen.     

山西榆次后沟堡子酒酒曲中优势酵母菌的分离鉴定

从榆次后沟堡子酒的酒曲中分离纯化酵母菌,得到了2株菌株S1和S2,并采用同化碳源试验、同化氮源试验、硝酸盐利用试验、生成类淀粉试验以及酵母菌的耐酒精性试验对其特性进行探索,结果如下:S1和S2菌株均不能利用甲醇作为碳源,对葡萄糖和蔗糖的利用情况也不同,S1菌株对葡萄糖的利用率最高,蔗糖次之;S2菌株对葡萄糖和蔗糖的利用情况相似;在葡萄糖和蔗糖利用方面,S1菌株较S2菌株同化率高。S1和S2菌株均能在所加氮源周围形成同化圈,表明二者对氮源的利用率很高;在硝酸盐利用试验中,S1和S2菌株所得结果均呈阳性反应,表明二者可以分泌大量胞外酶分解利用细胞外分子中的糖和蛋白质;S1和S2菌株均不能产生类淀粉物质;两株菌对酒精的耐受性也不相同,在同等酒精浓度下,S1菌株较S2菌株长势良好,12%为最适酒精度。     

Enhancement of symbiotic dinitrogen fixation by a toxin-releasing plant pathogen

An approximate doubling in plant growth, total plant nitrogen, nodulation, and overall dinitrogen fixation of alfalfa are the consequences of the action of a toxin delivered by a Pseudomonas infesting the alfalfa rhizosphere. The toxin, tabtoxinine-beta-lactam, inactivates selectively one form of glutamine synthetase in the nodules. Thus, normal glutamine synthetase-catalyzed ammonia assimilation is significantly impaired; yet these plants assimilated about twice the normal amount of nitrogen. How plants regulate dinitrogen fixing symbiotic associations is an important and unresolved question; the current results imply that the glutamine synthetase-catalyzed step in ammonia assimilation, a plant function, strongly influences overall dinitrogen fixation in legumes.     

施硫对不结球白菜硝酸盐累积及氮硫同化关键基因表达的影响

【目的】确定降低不结球白菜硝酸盐累积效果最佳的硫素形态,从转录水平筛选影响不结球白菜硝酸盐累积的关键基因,为完善不结球白菜科学施硫技术及进一步揭示硝酸盐累积分子调控机制、指导分子育种奠定基础。【方法】选取4种硫素形态及3个施用浓度处理不结球白菜,测定其对植株叶片及叶柄中硝酸盐含量的影响;利用半定量PCR技术从转录水平分析施硫对氮及硫代谢同化网络中30个基因表达的影响。【结果】不同形态硫处理均显著增加了不结球白菜的地上生物量,其中30 mg·kg^-1 Na₂SO₄处理的增幅最大,比对照增加49.76%,以Na₂SO₄处理的增幅最大。在降低小白菜硝酸盐含量中,以Na₂SO₄、Na₂S₂O₃处理效果相对显著,其中Na₂SO₄降低叶片中硝酸盐12.23%-23.55%,叶柄中33.08%-41.98%,降幅与浓度呈正相关,30 mg·kg^-1 Na₂SO₄处理的降幅最大;Na₂S₂O₃处理降低植株叶片中硝酸盐15.34%-33.08%,叶柄中11.95%-19.68%。硫处理在一定程度上促进氮同化,对照叶片中NR-1、NADH-GOGAT-1、NADH-GOGAT-2、Cytoplasm-GS-4、Cytoplasm-GS-5、GDH-3表达量低于其他处理,对照叶柄中NR-1、NADH-GOGAT-2、Cytoplasm-GS-1、GDH-2表达量低于其他处理,其中,各处理NADH-GOGAT-2表达量与叶片及叶柄中硝酸盐含量变化呈现一定规律性。硫处理对植株硫同化基因也产生一定影响,对照叶片中ATPS-2、ATPS-3、ATPS-4、APSR-3、SIR、SAT1.1、SAT2.1表达量较低,而对照叶柄中仅SIR、OASTL-A表达量明显低于其他处理。【结论】Na₂SO₄是降低不结球白菜硝酸盐效果较为显著的硫素,且能够显著提高产量,30 mg·kg^-1的Na₂SO₄为较优处理。NADH-GOGAT-2表达量与不结球白菜内硝酸盐含量呈负相关,推测其可能是影响氮同化的关键基因。     

去势对西门塔尔牛血清生化指标的影响

【目的】研究去势对西门塔尔牛血清能量、蛋白代谢及抗氧化指标的影响。【方法】选取50头健康的、16月龄的西门塔尔公牛,经药物驱虫后,依据体重进行单因素配对试验设计。【结果】肌酸激酶的活性去势组比未去势组低6.90;,差异显著（P＜0.05）。去势组的尿素氮和白蛋白含量比未去势组分别高5.63;和2.59;,差异极显著（P＜0.01）;白蛋白与球蛋白的比值去势组显著高于未去势组（P＜0.05）。去势组和未去势组的超氧化物歧化酶、谷胱甘肽过氧化物酶和丙二醛含量含量差异均不显著（P＞0.05）。【结论】去势使代谢氧化过程减慢,去势牛变得温顺而活动量相对减少,致使机体对ATP的需求降低了,血清肌酸激酶和乳酸脱氢酶的活性下降了,血糖的消耗降低,血清中血糖水平相对升高;蛋白同化作用减弱,血液的氧化应激变低。而白蛋白增加可能与去势牛需要更多的脂蛋白运势脂肪酸等营养物质有关。     

稀土元素处理对甘蔗体内氮素同化作用的影响研究

本文报道应用稀土元素处理甘蔗（Soccharum officinarum L.)叶片，分析测定了硝态氮、氨态氮、总氮、游氨基酸组分及游离氨基酸含量、硝酸还原酶（NR）活性等变化以及NR活性与硝态氮含量的关系。研究稀土元素处理对甘蔗体内氮素同化作用的影响。结果表明，应用100－600ppm稀土元素处理甘蔗叶片均能不同程度地减少其硝态氮含量，提高其氨态氮、总氮、游离氨基酸总含量以及NR活性，但游离氨基酸组分没发生变化，各处理浓度中以300ppm处理的效果为最显著，高浓度稀土元素处理则呈抑制效应。甘蔗叶片硝态氮含量与叶片NR活性具有平行关系，即凡硝态氮含量高，NR活性也高，凡硝态氮含量低，NR活性也低，以上结果，说明一定浓度范围的稀土元素处理能促进甘蔗的氮素同化作用。     

生物炭对冻融黑土中铵态氮和硝态氮淋失的影响

为了深入研究冻融条件下生物质炭对东北黑土中铵态氮和硝态氮淋失的影响效果,为解决冻融作用下黑土中无机氮素的淋失问题提供科学依据,采用室内模拟土柱淋溶实验方法研究了生物质炭对经过不同冻融循环次数处理土壤中铵态氮和硝态氮淋失的影响。研究结果表明:冻融会增加土壤氮素的淋失,且淋失量与冻融次数有关,施加生物质炭可以有效降低土壤因冻融作用引起的氮素淋失;玉米秸秆炭对无机氮素淋失降低率在76.15%~85.79%之间,树枝炭在55.26%~68.09%之间,可以看出玉米秸秆炭持氮效果较树枝炭更好;在冻融次数分别为3和1时,玉米秸秆炭和树枝炭持氮能力最强;两种生物质炭对铵态氮的固持能力均优于硝态氮。     

Nitrogen fixation by anaerobic cellulolytic bacteria

Four strains of anaerobic nitrogen-fixing, cellulose-fermenting bacteria were isolated in pure culture from freshwater mud and soil. Nitrogenase activity was demonstrated in these strains and also in several previously described anaerobic cellulolytic bacteria isolated from various natural environments. These are the first anaerobic bacteria known to use cellulose as an energy source for nitrogen fixation. Because cellulose is a plant polysaccharide that abounds in nature, these results raise the possibility that nitrogen-fixing, cellulose-fermenting bacteria may be widespread and thus play a major role in carbon and nitrogen cycling.