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Enhancing mainstream nitrogen removal by employing nitrate/nitrite-dependent anaerobic methane oxidation processes.
Liu, T, Hu, S, Guo, J
Critical reviews in biotechnology. 2019;(5):732-745
Abstract
Due to serious eutrophication in water bodies, nitrogen removal has become a critical stage for wastewater treatment plants (WWTPs) over past decades. Conventional biological nitrogen removal processes are based on nitrification and denitrification (N/DN), and are suffering from several major drawbacks, including substantial aeration consumption, high fugitive greenhouse gas emissions, a requirement for external carbon sources, excessive sludge production and low energy recovery efficiency, and thus unable to satisfy the escalating public needs. Recently, the discovery of anaerobic ammonium oxidation (anammox) bacteria has promoted an update of conventional N/DN-based processes to autotrophic nitrogen removal. However, the application of anammox to treat domestic wastewater has been hindered mainly by unsatisfactory effluent quality with nitrogen removal efficiency below 80%. The discovery of nitrate/nitrite-dependent anaerobic methane oxidation (n-DAMO) during the last decade has provided new opportunities to remove this barrier and to achieve a robust system with high-level nitrogen removal from municipal wastewater, by utilizing methane as an alternative carbon source. In the present review, opportunities and challenges for nitrate/nitrite-dependent anaerobic methane oxidation are discussed. Particularly, the prospective technologies driven by the cooperation of anammox and n-DAMO microorganisms are put forward based on previous experimental and modeling studies. Finally, a novel WWTP system acting as an energy exporter is delineated.
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2.
Influence of nitrogen status in wine alcoholic fermentation.
Gobert, A, Tourdot-Maréchal, R, Sparrow, C, Morge, C, Alexandre, H
Food microbiology. 2019;:71-85
Abstract
Nitrogen is an essential nutrient for yeast during alcoholic fermentation. Nitrogen is involved in the biosynthesis of protein, amino acids, nucleotides, and other metabolites, including volatile compounds. However, recent studies have called several mechanisms that regulate its role in biosynthesis into question. An initial focus on S. cerevisiae has highlighted that the concept of "preferred" versus "non-preferred" nitrogen sources is extremely variable and strain-dependent. Then, the direct involvement of amino acids consumed in the formation of proteins and volatile compounds has recently been reevaluated. Indeed, studies have highlighted the key role of lipids in nitrogen regulation in S. cerevisiae and their involvement in the mechanism of cell death. New winemaking strategies using non-Saccharomyces yeast strains in co- or sequential fermentation improve nitrogen management. Indeed, recent studies show that non-Saccharomyces yeasts have significant and specific needs for nitrogen. Moreover, sluggish fermentation can occur when they are associated with S. cerevisiae, necessitating nitrogen addition. In this context, we will present the consequences of nitrogen addition, discussing the sources, time of addition, transcriptome changes, and effect on volatile compound composition.
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3.
New discoveries in bacterial N-glycosylation to expand the synthetic biology toolbox.
Nothaft, H, Szymanski, CM
Current opinion in chemical biology. 2019;:16-24
Abstract
Historically, protein glycosylation was believed to be restricted to eukaryotes, but now is abundantly represented in all three domains of life. The first bacterial N-linked glycosylation system was discovered in the Gram-negative pathogen, Campylobacter jejuni, and subsequently transferred into the heterologous Escherichia coli host beginning a new era of synthetic bacterial glycoengineering. Since then, additional N-glycosylation pathways have been characterized resembling the classical C. jejuni system and unconventional new approaches for N-glycosylation have been uncovered. These include cytoplasmic protein modification, direct glycan transfer to proteins, and use of alternate amino acid acceptors, deepening our understanding of the vast mechanisms bacteria possess for protein modification and providing opportunities to expand the glycoengineering toolbox for designing novel vaccine formulations and protein therapeutics.
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4.
Integration of sulfate assimilation with carbon and nitrogen metabolism in transition from C3 to C4 photosynthesis.
Jobe, TO, Zenzen, I, Rahimzadeh Karvansara, P, Kopriva, S
Journal of experimental botany. 2019;(16):4211-4221
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Abstract
The first product of sulfate assimilation in plants, cysteine, is a proteinogenic amino acid and a source of reduced sulfur for plant metabolism. Cysteine synthesis is the convergence point of the three major pathways of primary metabolism: carbon, nitrate, and sulfate assimilation. Despite the importance of metabolic and genetic coordination of these three pathways for nutrient balance in plants, the molecular mechanisms underlying this coordination, and the sensors and signals, are far from being understood. This is even more apparent in C4 plants, where coordination of these pathways for cysteine synthesis includes the additional challenge of differential spatial localization. Here we review the coordination of sulfate, nitrate, and carbon assimilation, and show how they are altered in C4 plants. We then summarize current knowledge of the mechanisms of coordination of these pathways. Finally, we identify urgent questions to be addressed in order to understand the integration of sulfate assimilation with carbon and nitrogen metabolism particularly in C4 plants. We consider answering these questions to be a prerequisite for successful engineering of C4 photosynthesis into C3 crops to increase their efficiency.
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5.
How Does Evolution in Phosphorus-Impoverished Landscapes Impact Plant Nitrogen and Sulfur Assimilation?
Prodhan, MA, Finnegan, PM, Lambers, H
Trends in plant science. 2019;(1):69-82
Abstract
Phosphorus (P) fertilisers, made from rock phosphate, are used to attain high crop yields. However, rock phosphate is a finite resource and excessive P fertilisers pollute our environment, stressing the need for more P-efficient crops. Some Proteaceae have evolved in extremely P-impoverished environments. One of their adaptations is to curtail the abundance of ribosomal RNA, and thus protein, and tightly control the acquisition and assimilation of nitrogen (N) and sulfur. This differs fundamentally from plants that evolved in environments where N limits plant productivity, but is likely common in many species that evolved in P-impoverished landscapes. Here, we scrutinise the relevance of these responses towards developing P-efficient crops, focusing on plant species where 'P is in the driver's seat'.
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6.
Impact of Nitrogen Nutrition on Cannabis sativa: An Update on the Current Knowledge and Future Prospects.
Landi, S, Berni, R, Capasso, G, Hausman, JF, Guerriero, G, Esposito, S
International journal of molecular sciences. 2019;(22)
Abstract
Nitrogen (N) availability represents one of the most critical factors affecting cultivated crops. N is indeed a crucial macronutrient influencing major aspects, from plant development to productivity and final yield of lignocellulosic biomass, as well as content of bioactive molecules. N metabolism is fundamental as it is at the crossroad between primary and secondary metabolic pathways: Besides affecting the synthesis of fundamental macromolecules, such as nucleic acids and proteins, N is needed for other types of molecules intervening in the response to exogenous stresses, e.g. alkaloids and glucosinolates. By partaking in the synthesis of phenylalanine, N also directly impacts a central plant metabolic 'hub'-the phenylpropanoid pathway-from which important classes of molecules are formed, notably monolignols, flavonoids and other types of polyphenols. In this review, an updated analysis is provided on the impact that N has on the multipurpose crop hemp (Cannabis sativa L.) due to its renewed interest as a multipurpose crop able to satisfy the needs of a bioeconomy. The hemp stalk provides both woody and cellulosic fibers used in construction and for biocomposites; different organs (leaves/flowers/roots) are sources of added-value secondary metabolites, namely cannabinoids, terpenes, flavonoids, and lignanamides. We survey the available literature data on the impact of N in hemp and highlight the importance of studying those genes responding to both N nutrition and abiotic stresses. Available hemp transcriptomic datasets obtained on plants subjected to salt and drought are here analyzed using Gene Ontology (GO) categories related to N metabolism. The ultimate goal is to shed light on interesting candidate genes that can be further studied in hemp varieties growing under different N feeding conditions and showing high biomass yield and secondary metabolite production, even under salinity and drought.
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7.
Organic geochemical approaches to understanding early life.
Alleon, J, Summons, RE
Free radical biology & medicine. 2019;:103-112
Abstract
Here we discuss the early geological record of preserved organic carbon and the criteria that must be applied to distinguish biological from non-biological origins. Sedimentary graphite, irrespective of its isotopic composition, does not constitute a reliable biosignature because the rocks in which it is found are generally metamorphosed to the point where convincing signs of life have been erased. Rather, multiple lines of evidence, including sedimentary textures, microfossils, large accumulations of organic matter and isotopic data for co-existing carbon, nitrogen and sulfur are required before biological origin can be convincingly demonstrated.
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8.
Metal regulation of metabolism.
Bloom, AJ
Current opinion in chemical biology. 2019;:33-38
Abstract
A broad range of biochemicals, from proteins to nucleic acids, function properly only when associated with a metal, usually a divalent cation. Not any divalent metal will do: these metals differ in their ionic radius, dissociation in water, ionization potential, and number of unpaired electrons in their outer shells, and so substituting one metal for another often changes substrate positioning, redox reactivities, and physiological performance, and thus may serve as a regulatory mechanism. For instance, exchanging manganese for magnesium in several chloroplast enzymes maintains plant carbon-nitrogen balance under rising atmospheric CO2 concentrations. Here, we review this and a few other cases where association of proteins or nucleic acids with different metals control metabolism.
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9.
Nitrogen chlorosis in unicellular cyanobacteria - a developmental program for surviving nitrogen deprivation.
Forchhammer, K, Schwarz, R
Environmental microbiology. 2019;(4):1173-1184
Abstract
Cyanobacteria evolved sophisticated mechanisms allowing them to cope with environmental depletion of combined nitrogen. Here, we describe progress in understanding the processes involved in acclimation of nondiazotrophic cyanobacteria to nitrogen shortage, known as nitrogen chlorosis. The process includes immediate metabolic changes and degradation of light harvesting complexes as well as long-term acclimation responses. Consequently, quiescent cells substantially differing from vegetative cells are obtained. Thus, the process leading to these considerable metabolic and morphological changes is referred to as a developmental program. Current understanding of the relevant regulatory processes depicts an intricate mechanism involving modulation of transcription activators by proteinaceous interacting components, as well as by small metabolites reporting the energy status and carbon-nitrogen balance of the cell. In addition, we describe in detail the quiescent state characterizing cells under prolonged starvation and the process of recovery from this dormant chlorotic state. Accumulated data provide an in depth understanding of the mechanisms accompanying the cycling of cyanobacterial cells between vegetative growth, the quiescent-state and the recovery program, allowing them to regain proliferative growth upon nutrient replenishment.
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10.
Root phenotypes for improved nutrient capture: an underexploited opportunity for global agriculture.
Lynch, JP
The New phytologist. 2019;(2):548-564
Abstract
Nutrient-efficient crops are a solution to the two grand challenges of modern agriculture: improving food security while reducing environmental impacts. The primary challenges are (1) nitrogen (N) and phosphorus (P) efficiency; (2) potassium (K), calcium (Ca), and magnesium (Mg) efficiency for acid soils; and (3) iron (Fe) and zinc (Zn) efficiency for alkaline soils. Root phenotypes are promising breeding targets for each of these. The Topsoil Foraging ideotype is beneficial for P capture and should also be useful for capture of K, Ca, and Mg in acid soils. The Steep, Cheap, and Deep ideotype for subsoil foraging is beneficial for N and water capture. Fe and Zn capture can be improved by targeting mechanisms of metal mobilization in the rhizosphere. Root hairs and phenes that reduce the metabolic cost of soil exploration should be prioritized in breeding programs. Nutrient-efficient crops should provide benefits at all input levels. Although our current understanding is sufficient to deploy root phenotypes for improved nutrient capture in crop breeding, this complex topic does not receive the resources it merits in either applied or basic plant biology. Renewed emphasis on these topics is needed in order to develop the nutrient-efficient crops urgently needed in global agriculture.