Nitrogen Metabolic Processes Research Articles

Metabolic insights into the interaction between nitrogen removal and 4–chlorophenol reduction of anammox consortia

The response characteristic and performance stabilization of anammox process under the stress of the potential organic pollutants support the application of ammonia–nitrogen wastewater treatment. In the present study, nitrogen removal performance was significantly suppressed with the addition of 4–chlorophenol. The activity of anammox process was inhibited by 14.23% (0.1 mg/L), 20.54% (1 mg/L) and 78.15% (10 mg/L), respectively. Metagenomic analysis revealed a significant decrease in the abundance of KEGG pathways associated with carbohydrate and amino acid metabolism with increasing 4–chlorophenol concentration. Metabolic pathway profiles suggest that putrescine is down–regulated at high 4–chlorophenol stress due to inhibition of nitrogen metabolism processes, while it is up–regulated to reduce oxidative damage. In addition, the presence of 4–chlorophenol induced an enhancement of EPS and bacterial debris decomposition, and a partial conversion of 4–chlorophenol to p–nitrophenol. This study unravels the mechanism of effect on anammox consortia in response to 4–CP, which could provide supplementary to facilitate its full-scale application.

Microbial community structure and antibiotic resistance profiles in sediments with long-term aquaculture history

The aim of this investigation was to examine the microbial populations and their resistance patterns towards antibiotics, including the impact of nitrogen metabolism in response to the reintroduction of antibiotics, as well as the presence of resistance genes in sediments from shrimp ponds that have been utilized for extended periods of 5, 15, and over 30 years. Results showed that the sediments exhibited a high prevalence of Proteobacteria, Bacteroidetes, Planctomycetes, Chloroflexi, and Oxyphotobacteria as the most abundant bacterial phyla, accounting for 70.35–77.43% of the total bacterial community. The five most abundant phyla of fungi detected in all sediments, namely Rozellomycota, Ascomycota, Aphelidiomycota, Basidiomycota, and Mortierellomycota, constituted 24.26–32.54% of the total fungal community. It was highly probable that the Proteobacteria and Bacteroidetes phyla serve as the primary reservoir of antibiotic-resistant bacteria (ARB) in the sediment, which included various genera like Sulfurovum, Woeseia, Sulfurimonas, Desulfosarcina, and Robiginitalea. Among these genera, Sulfurovum appeared to be the most widespread in the sediment of aquaculture ponds that have been in operation for more than three decades, while Woeseia dominated in ponds that have been recently reclaimed and have a 15-year aquaculture history. Antibiotic resistance genes (ARGs) were categorized into seven distinct groups according to their mechanism of action. The prevalence of multidrug-resistant ARGs was found to be the highest among all types, with an abundance ranging from 8.74 × 10−2 to 1.90 × 10−1 copies per 16S rRNA gene copies. The results of a comparative analysis of sediment samples with varying aquaculture histories indicated that the total relative abundance of ARGs was significantly diminished in sediment with a 15-year aquaculture history as opposed to sediment with either a 5-year or 30-year aquaculture history. Another assessment of antibiotic resistances in aquaculture sediments involved an examination of the effects of reintroducing antibiotics on nitrogen metabolism processes. The findings revealed that the rates of ammonification, nitrification, and denitrification in the sediment with a history of 5 years and 15 years, decreased as the concentration of oxytetracycline increased from 1 to 300, and 2000 mg/kg, and inhibitory effects were found to be less pronounced in sediments with a 5-year history compared to those with a 15-year history. In contrast, oxytetracycline exposure led to a significant decrease in the rates of these processes in aquaculture pond sediments with a >30 years of aquaculture history across all the concentrations tested. The emergence and dissemination of antibiotic resistance profiles in aquaculture environments requires attention in future aquaculture management.

Comparative physiological and proteomic response to phosphate deficiency between two wheat genotypes differing in phosphorus utilization efficiency

Genetic variation in phosphorus utilization efficiency (PUE) widely exists among wheat genotypes. However, the underlying mechanisms are still unclear. Two contrasting wheat genotypes, Heng4399 (H4399) and Tanmai98 (TM98), were screened out from 17 bread wheat genotypes based on shoot soluble phosphate (Pi) concentrations. The TM98 had a significantly higher PUE than the H4399, especially under Pi deficiency. The induction of genes in the PHR1-centered Pi signaling pathway was significantly higher in TM98 than in H4399. Collectively, through a label-free quantitative proteomic analysis, 2110 high-confidence proteins were identified in shoots of the two wheat genotypes. Among them, 244 and 133 proteins were differentially accumulated under Pi deficiency in H4399 and TM98, respectively. The abundance of proteins related to nitrogen and phosphorus metabolic processes, small molecule metabolic process, and carboxylic acid metabolic process weas significantly affected by Pi deficiency in the shoots of the two genotypes. The abundance of proteins in energy metabolism, especially photosynthesis, was decreased by Pi deficiency in the shoots of H4399. Inversely, the PUE-efficient genotype TM98 could maintain protein abundance in energy metabolism. Moreover, the proteins involved in pyruvate metabolism, glutathione metabolism, and sulfolipid biosynthesis were significantly accumulated in TM98, which probably contributed to its high PUE. SignificanceImproving the PUE of wheat is urgent and crucial for sustainable agriculture. Genetic variation among wheat genotypes provides materials for exploring the underlying mechanisms for high PUE. This study selected two wheat genotypes with contrasting PUE to reveal the differences in the physiological and proteomic responses to phosphate deficiency. The PUE-efficiency genotype TM98 greatly induced the expression of genes in the PHR1-centered Pi signaling pathway. Subsequently, the TM98 could maintain the abundance of proteins related to energy metabolism and enhance the abundance of proteins involved in pyruvate metabolism, glutathione metabolism, and sulfolipid biosynthesis to increase PUE under Pi deficiency. The differentially expressed genes or proteins between the genotypes with contrasting PUE would provide potential and basis for breeding wheat varieties with improved phosphorus use efficiency.

Functional characterization of the GhNRT2.1e gene reveals its significant role in improving nitrogen use efficiency in Gossypium hirsutum.

Nitrate is the primary type of nitrogen available to plants, which is absorbed and transported by nitrate transporter 2 (NRT2) at low nitrate conditions. Genome-wide identification of NRT2 genes in G. hirsutum was performed. Gene expression patterns were revealed using RNA-seq and qRT-PCR. Gene functions were characterized using overexpression in A. thaliana and silencing in G. hirsutum. Protein interactions were verified by yeast two-hybrid and luciferase complementation imaging (LCI) assays. We identified 14, 14, seven, and seven NRT2 proteins in G. hirsutum, G. barbadense, G. raimondii, and G. arboreum. Most NRT2 proteins were predicted in the plasma membrane. The NRT2 genes were classified into four distinct groups through evolutionary relationships, with members of the same group similar in conserved motifs and gene structure. The promoter regions of NRT2 genes included many elements related to growth regulation, phytohormones, and abiotic stresses. Tissue expression pattern results revealed that most GhNRT2 genes were specifically expressed in roots. Under low nitrate conditions, GhNRT2 genes exhibited different expression levels, with GhNRT2.1e being the most up-regulated. Arabidopsis plants overexpressing GhNRT2.1e exhibited increased biomass, nitrogen and nitrate accumulation, nitrogen uptake and utilization efficiency, nitrogen-metabolizing enzyme activity, and amino acid content under low nitrate conditions. In addition, GhNRT2.1e-silenced plants exhibited suppressed nitrate uptake and accumulation, hampered plant growth, affected nitrogen metabolism processes, and reduced tolerance to low nitrate. The results showed that GhNRT2.1e could promote nitrate uptake and transport under low nitrate conditions, thus effectively increasing nitrogen use efficiency (NUE). We found that GhNRT2.1e interacts with GhNAR2.1 by yeast two-hybrid and LCI assays. Our research lays the foundation to increase NUE and cultivate new cotton varieties with efficient nitrogen use.

Insights on nitrogen and phosphorus removal mechanism in a single-stage Membrane Aeration Biofilm Reactor (MABR) dominated by denitrifying phosphorus removal coupled with anaerobic/aerobic denitrification

In the study, the denitrifying phosphorus removal process coupled with anaerobic/aerobic denitrification was started in a single-stage Membrane Aeration Biofilm Reactor (MABR). When the influent NO3−-N was 50.2 mg/L and the total phosphorus (TP) was 30.5 mg/L, the maximum Total Inorganic Nitrogen Removal Efficiency (TINRE) can reach 99.79 % and the Total Phosphorus Removal Efficiency (TPRE) can reach 82.62 % without the addition of any flocculant or precipitant. The phosphorus content in the substrate sludge was 4.10 %–6.15 %, which was higher than that in the initial biofilm or activated sludge (1.27 %–1.83 %). Based on 16S rRNA sequencing technology, it was found that Phosphorus-Accumulating Organisms (PAOs, Acinetobacter, relative abundance 0.02 % to 1.92 %) and Denitrifying Phosphorus-Accumulating Organisms (DPAOs, Flavobacterium (0.26 % to 5.39 %), Bdellovibrio (0.12 % to 1.48 %), and Pseudomonas (2.29 % to 1.28 %)) played pivotal roles in phosphorus removal. The enzyme gene reads of Complex I and Complex V processes were much more than that of Complex II- Complex IV, which indicated that Complex I and Complex V can be the main process for oxidative phosphorylation in the MABR. Moreover, four inorganic nitrogen metabolic processes, Dissimilatory Nitrate Reduction to Ammonium (DNRA), Assimilatory Nitrate Reduction Ammonium (ANRA), nitrification, and denitrification were found. Nitrifiers (Nitrosomonas (0.09 % to 0.19 %), Nitrospira (2.48 % to 0.06 %)), denitrifiers (Dokdonella (6.95 % to 2.11 %), Denitratisoma (0.42 % to1.48 %)), and aerobic denitrifiers (Pseudomonas (2.29 % to 1.28 %) and Thauera (4.75 % to 1.78 %)) contributed to nitrogen removal in the MABR. This study provided insights into the removal mechanism of nitrogen and phosphorus in a single-stage MABR.

Mainstream wastewater treatment by polyaluminium ferric chloride (PAFC) flocculation and nitritation-denitritation membrane aerated biofilm reactor (MABR)

To reduce the carbon emission of sewage treatment, a novel adsorption-biodegradation (A-B) process, flocculation pretreatment as A-stage and nitritation-denitritation MABR as B-stage, was proposed in the study. It was found that 27.37 %–49.69 % of organics can be removed from actual wastewater by flocculation with polyaluminium ferric chloride (PAFC). The pretreated wastewater could be further treated by nitritation-denitritation MABR with low aeration pressure (2–5 kPa) without any extra organics. The NH4+-N, total nitrogen (TN), and chemical oxygen demand (COD) removal efficiency can reach 100 %, 84.04 %, and 98.54 %, respectively. It was also found that the relative abundances of ammonia-oxidizing bacteria (AOB) (3.81 %–4.76 %) and denitrifying bacteria (DB) (4.30 %–5.59 %) were higher than that of nitrite-oxidizing bacteria (NOB) (2.08 %–2.39 %) in the MABR even after 130 days of operation according to the microorganism identification by 16S rRNA sequencing technology. This implied that low oxygen aeration in MABR can prevent NOB from becoming dominant bacteria. Furthermore, it was found that there were indeed traces of anaerobic ammonia oxidation (Anammox) bacteria (0.04 %–0.08 %) and were closely surrounded by other microorganisms in the MABR based on fluorescence in situ hybridization (FISH) technology. In addition, the microbial nitrogen metabolism process in the MABR was further analyzed according to the Kyoto Encyclopedia of Genes and Genomes (KEGG). The promising mainstream A-B process proposed in this study was expected to achieve nitrogen removal with little carbon and energy consumption in wastewater treatment plants (WWTPs).

Bacterial diversity and metabolism in microbial consortium of non-axenic culture Tychonema sp. BBK16

We performed high-throughput sequencing of microbial community with cyanobacterium Tychonema sp. BBK16 and heterotrophic bacteria in vitro. Representatives of the phylum Pseudomonadota/Proteobacteria, the bacteria Hydrogenophaga, Sphingomonas, Paucibacter, Aminobacter, Devosia, Tahibacter, and Bosea dominate and coexist with the cyanobacterium for a long period of cultivation. It was found that this cyanobacterium is an edificator of this community providing the microbiome with organic matter. Metabolic features of heterotrophic bacteria based on reconstructed genomes are presented. The main processes of carbon and nitrogen metabolism in the biofilm are carbohydrate and amino acid metabolism, as well as processes regulating the relationships between members of this consortium. Hydrogenophaga sp. and Tychonema sp. BBK16 show carbon autotrophy due to the Calvin–Benson–Bassham (СВВ) cycle, while Sphingomonas sp. due to the glyoxylate pathway of metabolism. The biofilm also contains the anoxygenic photoheterotroph Bosea sp. using light energy to transform organic matter. Aminobacter sp. is an active degrader of complex organics, which possesses methylotrophy and supplies hydrogen for oxidation by Hydrogenophaga sp., Paucibacter sp., also supplies hydrogen for this community. Sphingomonas, Tychonema and Paucibacter release phosphate from organic compounds providing phosphorus to this consortium.

Global patterns of diversity and metabolism of microbial communities in deep-sea hydrothermal vent deposits

BackgroundWhen deep-sea hydrothermal fluids mix with cold oxygenated fluids, minerals precipitate out of solution and form hydrothermal deposits. These actively venting deep-sea hydrothermal deposits support a rich diversity of thermophilic microorganisms which are involved in a range of carbon, sulfur, nitrogen, and hydrogen metabolisms. Global patterns of thermophilic microbial diversity in deep-sea hydrothermal ecosystems have illustrated the strong connectivity between geological processes and microbial colonization, but little is known about the genomic diversity and physiological potential of these novel taxa. Here we explore this genomic diversity in 42 metagenomes from four deep-sea hydrothermal vent fields and a deep-sea volcano collected from 2004 to 2018 and document their potential implications in biogeochemical cycles.ResultsOur dataset represents 3635 metagenome-assembled genomes encompassing 511 novel and recently identified genera from deep-sea hydrothermal settings. Some of the novel bacterial (107) and archaeal genera (30) that were recently reported from the deep-sea Brothers volcano were also detected at the deep-sea hydrothermal vent fields, while 99 bacterial and 54 archaeal genera were endemic to the deep-sea Brothers volcano deposits. We report some of the first examples of medium- (≥ 50% complete, ≤ 10% contaminated) to high-quality (> 90% complete, < 5% contaminated) MAGs from phyla and families never previously identified, or poorly sampled, from deep-sea hydrothermal environments. We greatly expand the novel diversity of Thermoproteia, Patescibacteria (Candidate Phyla Radiation, CPR), and Chloroflexota found at deep-sea hydrothermal vents and identify a small sampling of two potentially novel phyla, designated JALSQH01 and JALWCF01. Metabolic pathway analysis of metagenomes provides insights into the prevalent carbon, nitrogen, sulfur, and hydrogen metabolic processes across all sites and illustrates sulfur and nitrogen metabolic “handoffs” in community interactions. We confirm that Campylobacteria and Gammaproteobacteria occupy similar ecological guilds but their prevalence in a particular site is driven by shifts in the geochemical environment.ConclusionOur study of globally distributed hydrothermal vent deposits provides a significant expansion of microbial genomic diversity associated with hydrothermal vent deposits and highlights the metabolic adaptation of taxonomic guilds. Collectively, our results illustrate the importance of comparative biodiversity studies in establishing patterns of shared phylogenetic diversity and physiological ecology, while providing many targets for enrichment and cultivation of novel and endemic taxa.6aUVBDbDZ6m8Eohc79dCDgVideo

Enrichment of DNRA bacteria: Shift of microbial community and its combination with anammox to promote TN removal

Both anammox and dissimilatory nitrate reduction to ammonium (DNRA) are important processes of nitrogen metabolism, coexisting in a variety of natural ecosystems. However, the combined nitrogen removal of DNRA bacteria and anammox bacteria has not been achieved under laboratory conditions. Here, an anammox coupled DNRA system was constructed, in which DNRA bacteria convert nitrate generated from anammox process to ammonia for anammox metabolism again. DNRA bacteria were enriched form 2.11 * 105 to 3.02 * 107 copies/ng DNA in a non-woven fabric membrane bioreactor under a high C/N ratio environment. After 137 days’ operation, ammonia production efficiency from nitrate reached 60.65%. By nrfA gene sequencing analysis, Geobacter, some strains of Desulfovibrio and Desulfobulbus and a strain of traditional denitrifying bacteria Thauera sp. MZIT exhibiting DNRA function accounted for 20% of all bacteria. Small amount of anammox bacteria were detected from the system through qPCR tests, indicating that this system can mimic the natural habitats where anammox and DNRA together contributed to enhancement of total nitrogen removal rates. This study illustrated that DNRA bacteria could be enriched at high C/N ratio and natural processes are reproducible through engineering precise control.

Comparative transcriptome analysis of Portunus trituberculatus in response to Vibrio parahaemolyticus and low salinity

Vibrio parahaemolyticus is a common pathogen of marine crustaceans and is responsible for large losses in aquaculture. Salinity is an important environmental factor, and abrupt changes in salinity can affect the immunity of crustaceans. In this study, we carried out a transcriptomic analysis under pathogenic infection and low salt stress, and conducted a comparative analysis of the differentially expressed genes (DEGs) after stimulation by the two factors. Illumina sequencing technology was used for the transcriptome sequencing of 27 hepatopancreas samples, and 178.77 G sequencing data and an average of 44,142,119 clean reads per sample were obtained. A total of 3,047 and 3,710 DEGs were found after V. parahaemolyticus infection and low salt stress, which included a number of innate immunity genes, such as Toll-like receptor (TLR), anti-lipopolysaccharide factor (ALF), lectin, and hemocyanin. In addition, 2,016 common DEGs were found, accounting for 42.52% of the total DEGs. Among these, 169 DEGs were up-regulated after pathogenic infection and down-regulated after low salt stress, and were mainly enriched in starch and sucrose metabolism, nitrogen metabolism, amino sugar and nucleotide sugar processes, and other pathways. Collectively, these results provide data support for the analysis of the immune mechanism of crabs against V. parahaemolyticus and will also help to clarify the molecular mechanism by which salinity affects immunity.

Analysis on the evolution of nitrogen metabolism process and nitrogen supply hinterland pattern in Beijing's food system

As one of the main human activities affecting the global nitrogen cycle, food production and consumption caused a series of environmental issues with nitrogen, especially in densely populated cities. To comprehensively quantify these issues of cities, Beijing's food system was chosen as a case to build a refined 18-node nitrogen metabolic network model based on environmental and external support, its nitrogen budgets was innovatively accounted from the perspective of “bigger food system”, which contained the nitrogen flows both involved in and driving food metabolic processes. Then the key nodes were identified according to the principle of contributing more than 10% of total nitrogen inputs and emissions. Based on above, China Multi-Regional Input-Output table was used to further examine its nitrogen supply hinterlands and identify the key supply drivers from the sectoral perspective. The results show that the total nitrogen input of Beijing's food system increased by 32.6% but the nitrogen output increased by 64.8% between 1979 and 2019. The (1) Crop cultivation, (2) Animal husbandry, and (11) Urban residents are not only key nitrogen input nodes but also key nitrogen emission nodes. Besides, they drove the external nitrogen supply to Beijing's food system, thus should be the key managed objects. Hebei, Heilongjiang and Tianjin are the largest inland nitrogen supply hinterlands, while the foreign nitrogen supply increased by 15.8% from 2007 to 2019. Technical assistance, economic compensation and trade strategy adjustment are good ways to reduce hinterlands' nitrogen supply pressure. This study provides targeted management suggestions for the nitrogen sustainable of food system in cities and the nitrogen coordination among regions.

The ecological roles of assembling genomes for Bacillales and Clostridiales in coal seams

Biogenic coalbed methane is produced by biological processes mediated by synergistic interactions of microbial complexes in coal seams. However, the ecological role of functional bacteria in biogenic coalbed methane remains poorly understood. Here, we studied the metagenome assembled genomes (MAGs) of Bacillales and Clostridiales from coal seams, revealing further expansion of hydrogen and acetogen producers involved in organic matter decomposition. In this study, Bacillales and Clostridiales were dominant orders (91.85± 0.94%) in cultured coal seams, and a total of 16 MAGs from six families, including Bacillus, Paenibacillus, Staphylococcus, Anaerosalibacter, Hungatella and Paeniclostridium, were reconstructed. These microbial groups possessed multiple metabolic pathways (glycolysis/gluconeogenesis, pentose phosphate, β-oxidation, TCA cycle, assimilatory sulfate reduction, nitrogen metabolism and encoding hydrogenase) that provided metabolic substrates (acetate and/or H2) for the methanogenic processes. Therein, the hydrogenase-encoding gene and hydrogenase maturation factors were merely found in all the Clostridiales MAGs. β-oxidation was the main metabolic pathway involved in short-chain fatty acid degradation and acetate production, and most of these pathways were detected and exhibited different operon structures in Bacillales MAGs. In addition, assimilatory sulfate reduction and nitrogen metabolism processes were also detected in some MAGs, and these processes were also closely related to acetate production and/or organic matter degradation according to their operon structures and metabolic pathways. In summary, this study enabled a better understanding of the ecological roles of Bacillales and Clostridiales in biogenic methane in coal seams based on a combination of bioinformatic techniques.

Autotrophic biological nitrogen removal in a bacterial-algal symbiosis system: Formation of integrated algae/partial-nitrification/anammox biofilm and metagenomic analysis

Bacterial and algal symbiosis systems have been gradually applied in wastewater treatment. In this study, an integrated algal/partial nitrification/anammox biofilm system (IAPNABS) was constructed through light cultivation. The diverse biofilm was formed under the light, which was demonstrated by metagenomic analysis. The external biofilm at the steady stage was dominated by algae and nitrifying bacteria. Specifically, Geitlerinema and Chlorella were the two main species of algae, accounting for 6.0% and 1.9%, respectively; Nitrosomonas_europaea was the dominant species of nitrifying bacteria (2.8%). Anammox bacteria were mainly found in the inner biofilm, with Candidatus Kuenenia Stuttgartiensis and Candidatus Brocadiaceae Bacterium B188 representing the dominant species (1.0% and 0.3%, respectively). This layered biofilm performed efficient nitrogen removal. When initial NH4+-N in the system was 100 ± 20 mg/L, the IAPNABS achieved highest NH4+-N and TN removal rate (8.9 mg/(L·h) and 6.3 mg/(L·h), respectively) after 8 h of light and 2 h of dark. The oxygen produced by the algae was consumed by nitrifying bacteria, which provided the anaerobic environment and the nitrite substrate to maintain the activity of anammox bacteria. The abundance of the key enzymes involved in nitrogen removal (e.g. ammonia monooxygenase (Amo), hydrazine dehydrogenase (Hdh) and hydrazine synthase (Hzs)) further demonstrated main nitrogen metabolic processes in the layered biofilm. This study provides a new idea for autotrophic nitrogen removal from wastewater, which can greatly reduce the additional oxygen supply requirement.

Simulating Microbial Functional Diversity Dynamics in Agricultural Soils: An Individual Based Modeling Approach

New agricultural soil model approaches based on the microbiome dynamics must be considered as they can contribute to understand microbiological soil processes directly linked to substrate metabolism and the influence of these processes on plant growth. The present work presents an approach to the modelling of the interactions of the soil microbial functional diversity with the plant in terms of functions associated to specific processes of organic Carbon and Nitrogen metabolism. The substrates transformations arising in the organic matter that enters as a part of an agricultural scheme are the base for define this metabolism. As result, it has been possible to simulate a rhizospheric soil based on the concept of complex system dynamics and Individual Based Modeling known too as Agent-Based Modeling in an agricultural management context. The explicit definition of the microbiome functional diversity and the processing of the structural elements Carbon and Nitrogen, allowed representing the functional dynamics of this complex system composed by microorganisms, Carbon, Nitrogen and the plant. The variables that reflect the biology and the adaptation to the rhizospheric environment characterized the microorganisms and the assemblage community patterns in time. The main simulations output are system glucose and nitrate levels and an approach to plant growth, all resultant from the metabolic process of the considered Carbon and Nitrogen consortia. The results indicate that the microorganism’s diversity assemblages and its functional expression have a fundamental role in terms of plant growth.

利用叶片荧光参数估算油蒿灌丛群落生态系统生产力

PDF HTML阅读 XML下载 导出引用 引用提醒 利用叶片荧光参数估算油蒿灌丛群落生态系统生产力 DOI: 10.5846/stxb202103210750 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金（32071842，31901366，32071843） Estimating ecosystem productivity from leaf chlorophyll fluorescence parameter in Artemisia ordosica shrub community Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:生态系统生产力（GEP）在全球碳循环中具有重要意义，但其准确估算仍然是一个挑战。近年来，叶绿素荧光和冠层GEP的关联成为生态学的研究热点，关系尚不清楚且存在广泛争议。于2015年对宁夏盐池毛乌素沙地荒漠灌木油蒿（Artemisia ordosica）灌丛生态系统碳交换（NEE）特征进行连续观测，使用多通道荧光监测仪对通量贡献区内油蒿叶片的实时荧光（Fs）和光下荧光（Fm'）进行原位连续监测，叶面积指数（LAI）、归一化植被指数（NDVI）以及环境因子同步观测。利用光合有效辐射（PAR）、LAI和实际光化学效率（ΦPSII）等参数构建基于叶绿素荧光的生态系统生产力（GEPChlF）模型，探究叶片和冠层尺度不同参数对环境因子波动的响应，比较分析GEPChlF和基于涡度相关法监测生态系统生产力（GEPEC）相关性及GEPChlF的适用性。研究发现，ΦPSII和NEE日变化规律一致，ΦPSII、GEPChlF和GEPEC由PAR控制，受空气温度（Ta）和饱和水汽压差（VPD）调控，土壤含水量（SWC）和ΦPSII呈显著正相关（P<0.01）。PAR处于400-800 μmol m-2 s-1时，GEPChlF与GEPEC线性关系最优，斜率为0.627（R2=0.67，P<0.01）；弱光下GEPChlF的低估可能是由于冠层实际光能拦截率高造成；强光下GEPChlF显著高于GEPEC，呈非线性关系，可能是GEPEC基于夜间温度敏感性所拟合的生态系统呼吸（Re）无法预测光呼吸部分所导致。GEPChlF具有荧光参数的特性，对环境波动更加敏感，和环境因子相关性优于GEPEC。结果表明，高辐射、极端温度、高蒸腾和干旱是限制叶片和冠层尺度下油蒿光合过程的主要胁迫因素。本研究构建的荒漠生态系统光合过程模型GEPChlF能够替代GEPEC作为一个良好的冠层尺度生态参数，所提出的空间尺度上推方法可为促进区域可持续发展提供数据支撑和决策参考。 Abstract:Accurate estimation of gross ecosystem productivity (GEP) remains a challenge despite its importance in the global carbon cycle. Recently, the relationship between chlorophyll fluorescence and canopy GEP becomes an important scientific concern in plant ecology. However, it remains unclear how they are linked at multiple spatial scales across the growing season. In this study, continuous measurements of net ecosystem CO2 exchange (NEE) were made in a desert shrub (Artemisia ordosica) ecosystem using eddy covariance (EC) technique from May to October 2015 in Mu Us desert. The real-time fluorescence (Fs) and fluorescence under light (Fm') were also measured in situ using the Monitoring-PAM multi-channel fluorometer. Leaf area index (LAI), the normalized difference vegetation index (NDVI), and environmental factors including photosynthetically active radiation (PAR), air temperature (Ta), vapor pressure deficit (VPD), soil water content (SWC) and precipitation (PPT) were measured simultaneously within the range of carbon flux contribution. We developed a chlorophyll fluorescence-based model with input variables of photochemical efficiency (ΦPSII), PAR, and LAI to estimate ecosystem productivity (GEPChlF). We then compared the applicability of GEPChlF with EC-based GEP (GEPEC) and examined the responses of different parameters to environmental factors at leaf and canopy scales. As a result, the diurnal pattern of ΦPSII was similar to that of NEE, being mainly controlled by PAR and modified positively by Ta and VPD (P<0.01). The ΦPSII had a significantly positive correlation with SWC (P<0.01). The GEPChlF agreed well with GEPEC when PAR was 400-800 μmol m-2 s-1, with a slope of 0.627 (R2=0.67, P<0.01). The GEPChlF was likely to be underestimated under low PAR, leading to a high light interception rate of canopy, thus resulting in a low absorbed photosynthetically active radiation (APAR) in the model. The GEPChlF was significantly higher than GEPEC under high PAR and their relationship was nonlinear, which may be due to Artemisia ordosica released excessive sunlight energy for photo-respiration, nitrogen metabolism, Miller reaction and other processes. It was noted that photo-respiration was difficult to predict accurately because the daytime ecosystem respiration (Re) was simulated on the basis of nocturnal temperature sensitivity. Compared with GEPEC, chlorophyll fluorescence-derived GEPChlF was more sensitive to environmental fluctuations and had a better relation with environmental factors. Our results confirmed that the GEPChlF from chlorophyll fluorescence-based model could replace GEPEC as a good ecological parameter at canopy scale in consideration of the plant physiological status. We found that excessive radiation, extreme temperature, high transpiration and drought were the main stress factors limiting the photosynthetic process of Artemisia ordosica at different spatial scales. The study provides a method for estimating ecosystem productivity under the stressed environmental conditions on the basis of monitoring chlorophyll fluorescence in relation to environmental factors. The present results may scientifically support decision-making for promoting regional sustainable development. 参考文献 相似文献 引证文献

The dynamics of soil microbial community structure and nitrogen metabolism influenced by agriculture practices and rainfall

Agriculture practices, such as fertilization and cultivation, inevitably modify the soil ecological environment by altering the soil microbial community structure and the nitrogen (N) metabolism processes. The influences of rainfall combined with agriculture practices on microbial community structure and soil N metabolism were not well understood. It is important to investigate the combined effects of rainfall and agriculture practices on the soil N metabolism in varied soil layers for better agriculture management. In this paper, the effects of fertilization, cultivation as well as rainfall on N metabolism related microorganisms and key functional genes at various depths in a vegetable field were investigated. Results showed that Soil microbial community structure of 30 cm depth is more sensitive to soil properties change. Nitrogen-fixing bacteria (NFB) was promoted (from 0.07% to 1.43%) after fertilization, and cultivation shifted the dominance of NFB from Ensifer to Bacillus in 20–30 cm soil layer. Denitrifier Pseudomonas in 20 cm (from 0.93 to 5.01%) and comammox Nitrospira in 30 cm (from 3.3% to 3.82%) were promoted after rainfall. Soil C/N is a major determinant of soil N metabolism-related microorganisms. Fertilization before rainfall and cultivation at 30 cm is recommended. The findings in this paper could provide the scientific basis for better agriculture management practices.

Targeting Nitrogen Metabolism and Transport Processes to Improve Plant Nitrogen Use Efficiency.

In agricultural cropping systems, relatively large amounts of nitrogen (N) are applied for plant growth and development, and to achieve high yields. However, with increasing N application, plant N use efficiency generally decreases, which results in losses of N into the environment and subsequently detrimental consequences for both ecosystems and human health. A strategy for reducing N input and environmental losses while maintaining or increasing plant performance is the development of crops that effectively obtain, distribute, and utilize the available N. Generally, N is acquired from the soil in the inorganic forms of nitrate or ammonium and assimilated in roots or leaves as amino acids. The amino acids may be used within the source organs, but they are also the principal N compounds transported from source to sink in support of metabolism and growth. N uptake, synthesis of amino acids, and their partitioning within sources and toward sinks, as well as N utilization within sinks represent potential bottlenecks in the effective use of N for vegetative and reproductive growth. This review addresses recent discoveries in N metabolism and transport and their relevance for improving N use efficiency under high and low N conditions.

A comparative proteomic study of cold responses in potato leaves

The potato is an important food crop worldwide. While potatoes are rich in nutrition, the production suffers from yield loss caused by frost and freezing. This study used a common potato cultivar, ‘Zhengshu 6’, as the study system to measure the changes in the contents of soluble protein, malondialdehyde (MDA), proline, and chlorophyll after 1, 3, 5, and 7 days of low temperature treatment. We performed two-dimensional electrophoresis (2-DE) in combination with liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) technology and identified 52 differentially expressed protein spots among these timepoints. Results showed that levels of soluble protein, MDA, and proline increased as the duration of the low temperature treatment increased, and the chlorophyll content decreased. The 52 identified protein spots were classified by function as involved in defense response, energy metabolism, photosynthesis, protein degradation, ribosome formation, signal transduction, cell movement, nitrogen metabolism, and other physiological processes, thus allowing potato plants to achieve metabolic balance at low temperatures.

Carbon and Nitrogen Isotope Composition of the Wood of Pinus sylvestris, Betula pendula and Populus tremula

Proportions of 13C/12C and 15N/14N isotopes were identified in different woody compartments of birch (Betula pendula Roth), pine (Pinus sylvestris L.) and aspen (Populus tremula L.) trunks in preforest-steppe and pine-birch forests of the Middle Urals using mass spectrometry. The data were analyzed and interpreted from the perspective of the biochemical processes of carbon and nitrogen metabolism in leaves, cambial tissue, trunk wood, branches, roots, and soil. A lighter isotopic composition of carbon is characteristic of the leaves and trunk cambium. The trunk wood is characterized by a basal trend for 13C enrichment. The 13C/12C ratio corresponds to the nitrogen content in the trunk wood tissues, indicating metabolic control of carbon fractionation in woody plants. The isotope composition of nitrogen in the trunk cambium was significantly depleted in 15N (δ15N varies from –1.5 to –3.5‰) and δ13C (δ13C varies from –28.3 to –25.8‰). Meanwhile the sapwood (δ15N varies from –2.6 to 1‰ and δ13C varies from –27.5 to –27.1‰) and heartwood (δ15N varies from –2.5 to –3.5‰ and δ13C varies from –26 to –24.5‰) were more enriched in 15N and 13C. The significant difference between the values of 13C and 15N isotope discrimination consequently in the different woody compartments of trunk should be taken into account when interpreting data of wood organic matter in the context of paleoclimate.

Transcriptomic responses to silver nanoparticles in the freshwater unicellular eukaryote Tetrahymena thermophila.

Currently, silver nanoparticles (AgNPs) are being increasingly used as biocides in various consumer products and if released in the environment they can affect non-target organisms. Therefore, understanding the toxicity mechanism is crucial for both the design of more efficient nano-antimicrobials and for the design of nanomaterials that are biologically and environmentally benign throughout their life-cycle. Here, the ciliate Tetrahymena thermophila was used to elucidate the mechanisms of action of AgNPs by analysing the gene expression profile by RNA-seq and the transcriptomic effects of AgNPs were compared to those induced by soluble silver salt, AgNO3. Exposure to AgNPs at sublethal concentrations for 24h induced phagocytosis, transport pathways, response to oxidative stress, glutathione peroxidase activity, response to stimulus, oxidation-reduction, proteolysis, and nitrogen metabolism process. Based on gene set enrichment analysis (GSEA), some biological processes appeared targets of both toxicants. In addition to many similarities in affected genes, some effects were triggered only by NPs, like phagocytosis, glutathione peroxidase activity, response to stimulus, protein phosphorylation and nitrogen metabolism process. This research provides evidence that AgNPs compared to AgNO3 at the same concentration of dissolved silver ions dysregulate a higher number of cellular pathways. These findings confirm that AgNPs can induce toxicity not only due to soluble silver ions released from the particles but also to particle intrinsic features.