Search results for "nitrate"
showing 10 items of 580 documents
The fnr Gene of Bacillus licheniformis and the Cysteine Ligands of the C-Terminal FeS Cluster
1998
Many of the O2-responsive gene regulators of bacteria are members of the fumarate nitrate reductase-cyclic AMP receptor protein family of transcriptional regulators (12, 13, 15, 17) with predicted structures similar to those of the cyclic AMP receptor protein (11). The Fnr (stands for fumarate nitrate reductase regulator) protein from Escherichia coli (FnrEc) controls the expression of a variety of genes, mainly of anaerobic respiration and metabolism (5, 13). It contains a N-terminal cluster of three essential cysteine residues which are supposed to bind together with Cys122 a [4Fe 4S]2+ cluster which is required for O2 sensing (4, 7, 8, 10, 16). A wide variety of gram-negative bacteria co…
One pot light assisted green synthesis, storage and antimicrobial activity of dextran stabilized silver nanoparticles.
2014
Background Green synthesis of nanomaterials finds the edge over chemical methods due to its environmental compatibility. Herein, we report green synthesis of silver nanoparticles (Ag NPs) mediated with dextran. Dextran was used as a stabilizer and capping agent to synthesize Ag NPs using silver nitrate (AgNO3) under diffused sunlight conditions. Results UV–vis spectra of as synthesized Ag nanoparticles showed characteristic surface plasmon band in the range from ~405-452 nm. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) studies showed spherical Ag NPs in the size regime of ~50-70 nm. Face centered cubic lattice of Ag NPs was confirmed by powder X-ray diffraction (PXRD…
Role of glutathione in the formation of the active form of the oxygen sensor FNR ([4Fe-4S]·FNR) and in the control of FNR function
2000
The oxygen sensor regulator FNR (fumarate nitrate reductase regulator) of Escherichia coli is known to be inactivated by O2 as the result of conversion of a [4Fe-4S] cluster of the protein into a [2Fe-2S] cluster. Further incubation with O2 causes loss of the [2Fe-2S] cluster and production of apoFNR. The reactions involved in cluster assembly and reductive activation of apoFNR isolated under anaerobic or aerobic conditions were studied in vivo and in vitro. In a gshA mutant of E. coli that was completely devoid of glutathione, the O2 tension for the regulatory switch for FNR-dependent gene regulation was decreased by a factor of 4–5 compared with the wild-type, suggesting a role for glutat…
Nitrate removal microbiology in woodchip bioreactors : a case-study with full-scale bioreactors treating aquaculture effluents
2020
Woodchip bioreactors are viable low-cost nitrate (NO3−) removal applications for treating agricultural and aquaculture discharges. The active microbial biofilms growing on woodchips are conducting nitrogen (N) removal, reducing NO3− while oxidizing the carbon (C) from woodchips. However, bioreactor age, and changes in the operating conditions or in the microbial community might affect the NO3− removal as well as potentially promote nitrous oxide (N2O) production through either incomplete denitrification or dissimilatory NO3− reduction to ammonium (DNRA). Here, we combined stable isotope approach, amplicon sequencing, and captured metagenomics for studying the potential NO3− removal rates, a…
Sedimentary humic substances from lakes in Latvia
1997
Humic and fulvic acids, isolated from sediments of lakes in different trophic states (Latvia) were studied. The humic substances (HS) were characterized by their elemental and functional composition, their spectral properties, and molecular mass. The humus properties strongly depend on the origin of the sedimentary HS. Substantial similarity between sedimentary HS from oligotrophic and dystrophic water bodies was found, unless the biology of these lakes greatly differs. Humic molecules from sediments of oligotrophic and dystrophic lakes are smaller, more uniform, and contain lower amounts of carboxyl- and hydroxyl-groups than HS from meso- and eutrophic water bodies. On the other hand, sedi…
Method for Reproducible Shipboard Segmented Flow Analysis Ammonium Measurement Using an In-House Reference Material for Quality Control
2021
Ammonium is a fundamental nutrient for phytoplankton growth in seawater and is a key component of the microbial loop. Ammonium measured in parallel with other nutrients is crucial in understanding the small temporal scale changes in oceanographic ecology. Despite the importance of measuring ammonium at sea, owing to its lability, there is no consensus on the best method. The lack of availability of certified reference materials for ammonium in seawater also makes it difficult to assess the accuracy and reproducibility of ammonium measurements. In this study we present a modified segmented flow analysis method using ortho-phthaldialdehyde (OPA) with fluorescence detection to measure ammonium…
Autochthonous organic matter promotes DNRA and suppresses N2O production in sediments of the coastal Baltic Sea
2021
Coastal environments are nitrogen (N) removal hot spots, which regulate the amount of land-derived N reaching the open sea. However, mixing between freshwater and seawater creates gradients of inorganic N and bioavailable organic matter, which affect N cycling. In this study, we compare nitrate reduction processes between estuary and offshore archipelago environments in the coastal Baltic Sea. Denitrification rates were similar in both environments, despite lower nitrate and carbon concentrations in the offshore archipelago. However, DNRA (dissimilatory nitrate reduction to ammonium) rates were higher at the offshore archipelago stations, with a higher proportion of autochthonous carbon. Th…
Influence of cultivation techniques and use of two nutritive solution with different electrical conductivity on the production and quality of cucumbe…
2009
The most suitable techniques and use of F1 hybrids enable greenhouse production to achieve high yields, with crops all year round. In Sicily, greenhouse production of cucumber is for fresh use (slicers), producing large fruit. The cultivation technique most suited to greenhouses is the vertical single stem. However, an innovative technique being proposed is of cultivation on a trellis, eliminating lower branches, and training the remaining branches upwards (vertical shoot positioning, VSP). Cucumbers in the south of Italy are grown as the main crop or as a catch crop between 2 main crops. The crop should be rotated on the same soil only after 3-4 years with another crop, unless the land is …
Some observations on the use of matrix modifiers in the determination of aluminum by electrothermal atomic absorption spectrophotometry
1989
Abstract Some evidence demonstrating that the use of matrix modifiers is necessary to obtain good calibration lines in the determination of aluminum by graphite furnace atomic absorption spectrophotometry is provided. It was found that the most sensitive results were obtained when Mg(NO 3 ) 2 was used instead of NH 4 H 2 PO 4 .
Pentaerithrityl tetranitrate improves angiotensin II induced vascular dysfunction via induction of heme oxygenase-1
2010
The organic nitrate pentaerythritol tetranitrate is devoid of nitrate tolerance, which has been attributed to the induction of the antioxidant enzyme heme oxygenase (HO)-1. With the present study, we tested whether chronic treatment with pentaerythritol tetranitrate can improve angiotensin II–induced vascular oxidative stress and dysfunction. In contrast to isosorbide-5 mononitrate (75 mg/kg per day for 7 days), treatment with pentaerythritol tetranitrate (15 mg/kg per day for 7 days) improved the impaired endothelial and smooth muscle function and normalized vascular and cardiac reactive oxygen species production (mitochondria, NADPH oxidase activity, and uncoupled endothelial NO synthase)…