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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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Phosphate and sulphate-mediated structure and stability of bone morphogenetic protein - 2 (BMP - 2): A spectroscopy enabled investigation.
Konar, M, Sahoo, H
International journal of biological macromolecules. 2019;:1123-1133
Abstract
Impact of different monovalent and divalent cationic salts of sulphates and phosphates on conformation and stability of BMP - 2 was unraveled by absorbance, fluorescence and circular dichroism (CD) spectroscopy. Increase in absorbance of protein confirms the ground-state complexation between salt and BMP - 2. Phosphate salts, with the exception of sodium phosphate quenched the fluorescence intensity. The nature of quenching was static, as revealed by temperature-dependent fluorescence studies (Stern-Volmer constant (KSV) decreased with rise in temperature). Moreover, kq (bimolecular quenching constant) was in the range of 1012 M-1 s-1, confirming binding of phosphate salts with the protein. Contrary to this, sulphate salts increased the fluorescence intensity and excited-state lifetime of BMP - 2 (2.668 ns), with the maximum calculated for 300 mM sodium sulphate (3.216 ns). Phosphates reduced the lifetime of protein, with the least observed in presence of 300 mM magnesium phosphate (1.480 ns). Thermal stability of the protein (Tm = 70.66 °C) was altered significantly upon interaction with phosphate salts; however, it did not vary significantly in case of sulphates (exception - magnesium sulphate). Experimental evidences confirm the role played by anionic group on protein conformation and stability and identifies monovalent and divalent cations as insignificant contributor.
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Physiology and Distribution of Archaeal Methanotrophs That Couple Anaerobic Oxidation of Methane with Sulfate Reduction.
Bhattarai, S, Cassarini, C, Lens, PNL
Microbiology and molecular biology reviews : MMBR. 2019;(3)
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Abstract
In marine anaerobic environments, methane is oxidized where sulfate-rich seawater meets biogenic or thermogenic methane. In those niches, a few phylogenetically distinct microbial types, i.e., anaerobic methanotrophs (ANME), are able to grow through anaerobic oxidation of methane (AOM). Due to the relevance of methane in the global carbon cycle, ANME have drawn the attention of a broad scientific community for 4 decades. This review presents and discusses the microbiology and physiology of ANME up to the recent discoveries, revealing novel physiological types of anaerobic methane oxidizers which challenge the view of obligate syntrophy for AOM. An overview of the drivers shaping the distribution of ANME in different marine habitats, from cold seep sediments to hydrothermal vents, is given. Multivariate analyses of the abundance of ANME in various habitats identify a distribution of distinct ANME types driven by the mode of methane transport. Intriguingly, ANME have not yet been cultivated in pure culture, despite intense attempts. Further advances in understanding this microbial process are hampered by insufficient amounts of enriched cultures. This review discusses the advantages, limitations, and potential improvements for ANME laboratory-based cultivation systems.
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Sulfate is transported at significant rates through the symbiosome membrane and is crucial for nitrogenase biosynthesis.
Schneider, S, Schintlmeister, A, Becana, M, Wagner, M, Woebken, D, Wienkoop, S
Plant, cell & environment. 2019;(4):1180-1189
Abstract
Legume-rhizobia symbioses play a major role in food production for an ever growing human population. In this symbiosis, dinitrogen is reduced ("fixed") to ammonia by the rhizobial nitrogenase enzyme complex and is secreted to the plant host cells, whereas dicarboxylic acids derived from photosynthetically produced sucrose are transported into the symbiosomes and serve as respiratory substrates for the bacteroids. The symbiosome membrane contains high levels of SST1 protein, a sulfate transporter. Sulfate is an essential nutrient for all living organisms, but its importance for symbiotic nitrogen fixation and nodule metabolism has long been underestimated. Using chemical imaging, we demonstrate that the bacteroids take up 20-fold more sulfate than the nodule host cells. Furthermore, we show that nitrogenase biosynthesis relies on high levels of imported sulfate, making sulfur as essential as carbon for the regulation and functioning of symbiotic nitrogen fixation. Our findings thus establish the importance of sulfate and its active transport for the plant-microbe interaction that is most relevant for agriculture and soil fertility.
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Sulfated Polysaccharides from Macroalgae for Bone Tissue Regeneration.
Venkatesan, J, Anil, S, Rao, S, Bhatnagar, I, Kim, SK
Current pharmaceutical design. 2019;(11):1200-1209
Abstract
BACKGROUND Utilization of macroalgae has gained much attention in the field of pharmaceuticals, nutraceuticals, food and bioenergy. Macroalgae has been widely consumed in Asian countries as food from ancient days and proved that it has potential bioactive compounds which are responsible for its nutritional properties. Macroalgae consists of a diverse range of bioactive compounds including proteins, lipids, pigments, polysaccharides, etc. Polysaccharides from macroalgae have been utilized in food industries as gelling agents and drug excipients in the pharmaceutical industries owing to their biocompatibility and gel forming properties. Exploration of macroalgae derived sulfated polysaccharides in biomedical applications is increasing recently. METHODS In the current review, we have provided information of three different sulfated polysaccharides such as carrageenan, fucoidan and ulvan and their isolation procedure (enzymatic precipitation, microwave assisted method, and enzymatic hydrolysis method), structural details, and their biomedical applications exclusively for bone tissue repair and regeneration. RESULTS From the scientific results on sulfated polysaccharides from macroalgae, we conclude that sulfated polysaccharides have exceptional properties in terms of hydrogel-forming ability, scaffold formation, and mimicking the extracellular matrix, increasing alkaline phosphatase activity, enhancement of biomineralization ability and stem cell differentiation for bone tissue regeneration. CONCLUSION Overall, sulfated polysaccharides from macroalgae may be promising biomaterials in bone tissue repair and regeneration.
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Competitive dynamics of anaerobes during long-term biological sulfate reduction process in a UASB reactor.
Chen, H, Wu, J, Liu, B, Li, YY, Yasui, H
Bioresource technology. 2019;:173-182
Abstract
To reveal the long-term competitive dynamics of anaerobes in anaerobic bioreactors with sulfate reduction, a comprehensive structured mathematical model was designed for an extension of the Anaerobic Digestion Model No. 1 (ADM1). Sulfate reduction bacteria (SRB) were categorized into acetogenic-likewise SRB (ASRB) and methanogenic-likewise SRB (MSRB). Experimental data from 329 days of continuous operation of a laboratory-scale upflow anaerobic sludge bed (UASB) reactor was used for model calibration and validation. Results show that the model has a good agreement with experimental data and that three stages including the MPA dominant, stalemate and SRB dominant stages were clearly appeared throughout the whole competition period. The model was capable of predicting the long-term dynamic competition of sulfidogens and methanogens for electrons. This could explain a long-term of over 200 days needed for the SRB out-competing the MPA, and support speculation that the SRB could finally out-compete both the AcB and the MPA.
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Sulfate transport systems in plants: functional diversity and molecular mechanisms underlying regulatory coordination.
Takahashi, H
Journal of experimental botany. 2019;(16):4075-4087
Abstract
Sulfate transporters are integral membrane proteins controlling the flux of sulfate (SO42-) entering the cells and subcellular compartments across the membrane lipid bilayers. Sulfate uptake is a dynamic biological process that occurs in multiple cell layers and organs in plants. In vascular plants, sulfate ions are taken up from the soil environment to the outermost cell layers of roots and horizontally transferred to the vascular tissues for further distribution to distant organs. The amount of sulfate ions being metabolized in the cytosol and chloroplast/plastid or temporarily stored in the vacuole depends on expression levels and functionalities of sulfate transporters bound specifically to the plasma membrane, chloroplast/plastid envelopes, and tonoplast membrane. The entire system for sulfate homeostasis, therefore, requires different types of sulfate transporters to be expressed and coordinately regulated in specific organs, cell types, and subcellular compartments. Transcriptional and post-transcriptional regulatory mechanisms control the expression levels and functions of sulfate transporters to optimize sulfate uptake and internal distribution in response to sulfate availability and demands for synthesis of organic sulfur metabolites. This review article provides an overview of sulfate transport systems and discusses their regulatory aspects investigated in the model plant species Arabidopsis thaliana.
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Growth of an anaerobic sulfate-reducing bacterium sustained by oxygen respiratory energy conservation after O2 -driven experimental evolution.
Schoeffler, M, Gaudin, AL, Ramel, F, Valette, O, Denis, Y, Hania, WB, Hirschler-Réa, A, Dolla, A
Environmental microbiology. 2019;(1):360-373
Abstract
Desulfovibrio species are representatives of microorganisms at the boundary between anaerobic and aerobic lifestyles, since they contain the enzymatic systems required for both sulfate and oxygen reduction. However, the latter has been shown to be solely a protective mechanism. By implementing the oxygen-driven experimental evolution of Desulfovibrio vulgaris Hildenborough, we have obtained strains that have evolved to grow with energy derived from oxidative phosphorylation linked to oxygen reduction. We show that a few mutations are sufficient for the emergence of this phenotype and reveal two routes of evolution primarily involving either inactivation or overexpression of the gene encoding heterodisulfide reductase. We propose that the oxygen respiration for energy conservation that sustains the growth of the O2 -evolved strains is associated with a rearrangement of metabolite fluxes, especially NAD+ /NADH, leading to an optimized O2 reduction. These evolved strains are the first sulfate-reducing bacteria that exhibit a demonstrated oxygen respiratory process that enables growth.
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Study of sulfate-reducing ammonium oxidation process and its microbial community composition.
Zhang, D, Cui, L, Wang, H, Liang, J
Water science and technology : a journal of the International Association on Water Pollution Research. 2019;(1):137-144
Abstract
In this study, the simultaneous removal of ammonium and sulfate was detected in a self-designed circulating flow reactor, in which ammonium oxidization was combined with sulfate reduction. The highest removal efficiencies of NH4 +-N and SO4 2-S were 92% and 59.2%. NO2 - and NO3 - appeared in the effluent, and experimental studies showed that increasing the proportion of N/S in the influent would increase the NO2 - concentration in the effluent. However, N/S [n(NH4 +-N)/n(SO4 2-S)] conversion rates during the experiment were between 2.1 and 12.9, which may have been caused by the experiment's complex process. The microbial community in the sludge reactor included Proteobacteria, Chloroflexi, Bacteroidetes, Chlorobi, Acidobacteria and Planctomycetes after 187 days of operation. Proteobacteria bacteria had a more versatile metabolism. The sulfate-reducing ammonium oxidation (SRAO) was mainly due to the high performance of Proteobacteria. Nitrospirae has been identified as the dominant functional bacteria in several anammox reactors used for nitrogen removal. Approximately 12.4% of denitrifying bacteria were found in the sludge. These results show that a portion of the nitrogen was converted by nitrification-denitrification, and that traditional anammox proceeds simultaneously with SRAO.
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Hydroxylated and sulfated metabolites of commonly occurring airborne polychlorinated biphenyls inhibit human steroid sulfotransferases SULT1E1 and SULT2A1.
Parker, VS, Squirewell, EJ, Lehmler, HJ, Robertson, LW, Duffel, MW
Environmental toxicology and pharmacology. 2018;:196-201
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Abstract
Polychlorinated biphenyls (PCBs) are ubiquitous environmental contaminants that are associated with varied adverse health effects. Lower chlorinated PCBs are prevalent in indoor and outdoor air and can be metabolized to their hydroxylated derivatives (OH-PCBs) followed by sulfation to form PCB sulfates. Sulfation is also a means of signal termination for steroid hormones. The human estrogen sulfotransferase (SULT1E1) and alcohol/hydroxysteroid sulfotransferase (SULT2A1) catalyze the formation of steroid sulfates that are inactive at steroid hormone receptors. We investigated the inhibition of SULT1E1 (IC50s ranging from 7.2 nM to greater than 10 μM) and SULT2A1 (IC50s from 1.3 μM to over 100 μM) by five lower-chlorinated OH-PCBs and their corresponding PCB sulfates relevant to airborne PCB-exposure. Several congeners of lower chlorinated OH-PCBs relevant to airborne PCB exposures were potent inhibitors of SULT1E1 and SULT2A1 and thus have the potential to disrupt regulation of intracellular concentrations of the receptor-active steroid substrates for these enzymes.