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Applied and Environmental Microbiology Apr 2023Nitrogen gas (N) fixation in the anode-respiring bacterium Geobacter sulfurreducens occurs through complex, multistep processes. Optimizing ammonium (NH) production from...
Nitrogen gas (N) fixation in the anode-respiring bacterium Geobacter sulfurreducens occurs through complex, multistep processes. Optimizing ammonium (NH) production from this bacterium in microbial electrochemical technologies (METs) requires an understanding of how those processes are regulated in response to electrical driving forces. In this study, we quantified gene expression levels (via RNA sequencing) of G. sulfurreducens growing on anodes fixed at two different potentials (-0.15 V and +0.15 V versus standard hydrogen electrode). The anode potential had a significant impact on the expression levels of N fixation genes. At -0.15 V, the expression of nitrogenase genes, such as , , and , significantly increased relative to that at +0.15 V, as well as genes associated with NH uptake and transformation, such as glutamine and glutamate synthetases. Metabolite analysis confirmed that both of these organic compounds were present in significantly higher intracellular concentrations at -0.15 V. N fixation rates (estimated using the acetylene reduction assay and normalized to total protein) were significantly larger at -0.15 V. Genes expressing flavin-based electron bifurcation complexes, such as electron-transferring flavoproteins (EtfAB) and the NADH-dependent ferredoxin:NADP reductase (NfnAB), were also significantly upregulated at -0.15 V, suggesting that these mechanisms may be involved in N fixation at that potential. Our results show that in energy-constrained situations (i.e., low anode potential), the cells increase per-cell respiration and N fixation rates. We hypothesize that at -0.15 V, they increase N fixation activity to help maintain redox homeostasis, and they leverage electron bifurcation as a strategy to optimize energy generation and use. Biological nitrogen fixation coupled with ammonium recovery provides a sustainable alternative to the carbon-, water-, and energy-intensive Haber-Bosch process. Aerobic biological nitrogen fixation technologies are hindered by oxygen gas inhibition of the nitrogenase enzyme. Electrically driving biological nitrogen fixation in anaerobic microbial electrochemical technologies overcomes this challenge. Using Geobacter sulfurreducens as a model exoelectrogenic diazotroph, we show that the anode potential in microbial electrochemical technologies has a significant impact on nitrogen gas fixation rates, ammonium assimilation pathways, and expression of genes associated with nitrogen gas fixation. These findings have important implications for understanding regulatory pathways of nitrogen gas fixation and will help identify target genes and operational strategies to enhance ammonium production in microbial electrochemical technologies.
Topics: Nitrogen Fixation; Ammonium Compounds; Geobacter; Electrodes; Nitrogenase; Nitrogen
PubMed: 36975810
DOI: 10.1128/aem.02073-22 -
International Journal of Molecular... Jan 2022Ammonium is a paradoxical nutrient because it is more metabolically efficient than nitrate, but also causes plant stresses in excess, i.e., ammonium toxicity. Current...
Ammonium is a paradoxical nutrient because it is more metabolically efficient than nitrate, but also causes plant stresses in excess, i.e., ammonium toxicity. Current knowledge indicates that ammonium tolerance is species-specific and related to the ammonium assimilation enzyme activities. However, the mechanisms underlying the ammonium tolerance in bedding plants remain to be elucidated. The study described herein explores the primary traits contributing to the ammonium tolerance in three bedding plants. Three NH:NO ratios (0:100, 50:50, 100:0) were supplied to salvia, petunia, and ageratum. We determined that they possessed distinct ammonium tolerances: salvia and petunia were, respectively, extremely sensitive and moderately sensitive to high NH concentrations, whereas ageratum was tolerant to NH, as characterized by the responses of the shoot and root growth, photosynthetic capacity, and nitrogen (amino acid and soluble protein)-carbohydrate (starch) distributions. An analysis of the major nitrogen assimilation enzymes showed that the root GS (glutamine synthetase) and NADH-GDH (glutamate dehydrogenase) activities in ageratum exhibited a dose-response relationship (reinforced by 25.24% and 6.64%, respectively) as the NH level was raised from 50% to 100%; but both enzyme activities were significantly diminished in salvia. Besides, negligible changes of GS activities monitored in leaves revealed that only the root GS and NADH-GDH underpin the ammonium tolerances of the three bedding plants.
Topics: Ammonium Compounds; Bedding and Linens; Glutamate-Ammonia Ligase; NAD; Nitrogen; Plant Roots; Plants
PubMed: 35162985
DOI: 10.3390/ijms23031061 -
PloS One 2020Alkyltrimethylammonium compounds (ATMACs), dialkyldimethylammonium compounds (DADMACs) and benzylalkyldimethylethylammonium compounds (BACs) are quaternary alkylammonium...
Alkyltrimethylammonium compounds (ATMACs), dialkyldimethylammonium compounds (DADMACs) and benzylalkyldimethylethylammonium compounds (BACs) are quaternary alkylammonium compounds (QAAC), which are released into the environment in large quantities after their use in cleaning agents and disinfectants. Despite their potential role as selective agents promoting resistance against QAACs as well as antibiotics, there is a lack of data for QAACs in soil due to the lack of sensitive analytical methods. Therefore, we present a robust and fast method for the extraction and quantification of concentrations of these compounds in soil and sewage sludge. The method is based on ultrasonic extraction (USE) with a mixture of acetonitrile and HCl followed by a solid phase extraction (SPE) cleaning step and a subsequent quantification of concentrations with high performance liquid chromatography with mass spectrometry (HPLC-MS/MS) in multi mass reaction mode (MRM). The proposed method is suitable for the quantification of ATMACs (chain length C-8 to C-16), BACs (C-8 to C-18) and DADMACs (C-8 to C-16). The achieved limits of quantification (LOQ) range from 0.1 μg kg-1 to 2.1 μg kg-1. The recovery rates of spiked soil samples for non-deuterated homologues were between 47% and 57%. The analysis of sewage sludge samples and soil samples revealed that BAC-C12 was the most abundant QAAC with concentrations up to 38600 μg kg-1 in sewage sludge and up to 81 μg kg-1 in a Mexican soil that was irrigated with wastewater. Overall, the presented methods open perspectives for effectively studying fate and effects of QAACs in soils.
Topics: Chromatography, High Pressure Liquid; Quaternary Ammonium Compounds; Sewage; Soil; Tandem Mass Spectrometry
PubMed: 32750078
DOI: 10.1371/journal.pone.0237020 -
Journal of the American Chemical Society May 2021The site-specific oxidation of strong C(sp)-H bonds is of uncontested utility in organic synthesis. From simplifying access to metabolites and late-stage diversification...
The site-specific oxidation of strong C(sp)-H bonds is of uncontested utility in organic synthesis. From simplifying access to metabolites and late-stage diversification of lead compounds to truncating retrosynthetic plans, there is a growing need for new reagents and methods for achieving such a transformation in both academic and industrial circles. One main drawback of current chemical reagents is the lack of diversity with regard to structure and reactivity that prevents a combinatorial approach for rapid screening to be employed. In that regard, directed evolution still holds the greatest promise for achieving complex C-H oxidations in a variety of complex settings. Herein we present a rationally designed platform that provides a step toward this challenge using -ammonium ylides as electrochemically driven oxidants for site-specific, chemoselective C(sp)-H oxidation. By taking a first-principles approach guided by computation, these new mediators were identified and rapidly expanded into a library using ubiquitous building blocks and trivial synthesis techniques. The ylide-based approach to C-H oxidation exhibits tunable selectivity that is often exclusive to this class of oxidants and can be applied to real-world problems in the agricultural and pharmaceutical sectors.
Topics: Ammonium Compounds; Electrochemical Techniques; Molecular Structure; Oxidation-Reduction
PubMed: 33983721
DOI: 10.1021/jacs.1c03780 -
Water Research Apr 2023Rapid sand filters (RSF) are an established and widely applied technology for groundwater treatment. Yet, the underlying interwoven biological and physical-chemical...
Rapid sand filters (RSF) are an established and widely applied technology for groundwater treatment. Yet, the underlying interwoven biological and physical-chemical reactions controlling the sequential removal of iron, ammonia and manganese remain poorly understood. To resolve the contribution and interactions between the individual reactions, we studied two full-scale drinking water treatment plant configurations, namely (i) one dual-media (anthracite and quartz sand) filter and (ii) two single-media (quartz sand) filters in series. In situ and ex situ activity tests were combined with mineral coating characterization and metagenome-guided metaproteomics along the depth of each filter. Both plants exhibited comparable performances and process compartmentalization, with most of ammonium and manganese removal occurring only after complete iron depletion. The homogeneity of the media coating and genome-based microbial composition within each compartment highlighted the effect of backwashing, namely the complete vertical mixing of the filter media. In stark contrast to this homogeneity, the removal of the contaminants was strongly stratified within each compartment, and decreased along the filter height. This apparent and longstanding conflict was resolved by quantifying the expressed proteome at different filter heights, revealing a consistent stratification of proteins catalysing ammonia oxidation and protein-based relative abundances of nitrifying genera (up to 2 orders of magnitude difference between top and bottom samples). This implies that microorganisms adapt their protein pool to the available nutrient load at a faster rate than the backwash mixing frequency. Ultimately, these results show the unique and complementary potential of metaproteomics to understand metabolic adaptations and interactions in highly dynamic ecosystems.
Topics: Manganese; Iron; Ammonium Compounds; Ammonia; Quartz; Ecosystem; Groundwater; Filtration; Water Purification
PubMed: 36868119
DOI: 10.1016/j.watres.2023.119805 -
Carryover effects of chronic exposure to ammonium during the larval stage on post-metamorphic frogs.Aquatic Toxicology (Amsterdam,... Jul 2022Water contamination poses an important challenge to aquatic fauna, including well-documented effects on amphibian larvae. However, little is known about how...
Water contamination poses an important challenge to aquatic fauna, including well-documented effects on amphibian larvae. However, little is known about how contamination during the larval stages may affect post-metamorphic phases, or whether resistance may have evolved in some populations. In this work, we tested the hypothesis that chronic exposure to ammonium (a common contaminant in agroecosystems with confirmed effects on anuran tadpoles) during the larval stage of Pelophylax perezi frogs would affect growth and locomotor performance of metamorph, juvenile, subadult and adult stages. We also predicted that the effects of ammonium would be milder in offspring originated from parental agroecosystem frogs than those originating from forests. We compared tadpoles from both habitats either reared in untreated water or chronically exposed to ammonium. We found that exposure to ammonium during the larval stage inflicted effects on morphology (different measures of body size) and swimming speed after metamorphosis until adulthood. However, these effects were not always consistent through post-metamorphic stages and the effects differed as a function of treatment and habitat. In adults, body size and condition were greater in non-ammonium and ammonium exposed individuals, respectively. These differences were not detectable in metamorphs, for which only ammonium-exposed individuals from agroecosystem showed reduced body size in intermediate post-metamorphic stages. In turn, treatment reduced jumping distance only in agroecosystem adults, subadults and juveniles, which was opposite to the trend observed just after metamorphosis. These changes of patterns throughout the ontogeny of P. perezi could be due to processes such as compensatory growth, delayed energy costs derived from it, or early sexual differences that could be present even before they can be accounted for. In summary, this study suggests that exposure to ammonium during larval stages can result in diverse biological and long-term outcomes in later life stages.
Topics: Adult; Ammonium Compounds; Animals; Anura; Humans; Larva; Metamorphosis, Biological; Water; Water Pollutants, Chemical
PubMed: 35598377
DOI: 10.1016/j.aquatox.2022.106196 -
Environmental Science & Technology Aug 2023Bioelectrochemical systems (BESs) are considered to be energy-efficient to convert ammonium, which is present in wastewater. The application of BESs as a technology to...
Bioelectrochemical systems (BESs) are considered to be energy-efficient to convert ammonium, which is present in wastewater. The application of BESs as a technology to treat wastewater on an industrial scale is hindered by the slow removal rate and lack of understanding of the underlying ammonium conversion pathways. This study shows ammonium oxidation rates up to 228 ± 0.4 g-N m d under microoxic conditions (dissolved oxygen at 0.02-0.2 mg-O/L), which is a significant improvement compared to anoxic conditions (120 ± 21 g-N m d). We found that this enhancement was related to the formation of hydroxylamine (NHOH), which is rate limiting in ammonium oxidation by ammonia-oxidizing microorganisms. NHOH was intermediate in both the absence and presence of oxygen. The dominant end-product of ammonium oxidation was dinitrogen gas, with about 75% conversion efficiency in the presence of a microoxic level of dissolved oxygen and 100% conversion efficiency in the absence of oxygen. This work elucidates the dominant pathways under microoxic and anoxic conditions which is a step toward the application of BESs for ammonium removal in wastewater treatment.
Topics: Ammonium Compounds; Wastewater; Bioreactors; Oxidation-Reduction; Oxygen; Nitrogen
PubMed: 37498945
DOI: 10.1021/acs.est.3c02227 -
Molecules (Basel, Switzerland) Apr 2019Methacrylate analogs of quaternary ammonium salts functionalized with carboxylic (AMadh1 68.8% yield, AMadh2 53.2% yield) and methoxysilane (AMsil1 94.8% yield, AMsil2...
Methacrylate analogs of quaternary ammonium salts functionalized with carboxylic (AMadh1 68.8% yield, AMadh2 53.2% yield) and methoxysilane (AMsil1 94.8% yield, AMsil2 36.0% yield) groups were synthesized via Menschutkin reaction. Fourier-transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (H, C and 2D H-C heteronuclear single quantum coherence (HSQC) NMR), mass spectrometry, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were utilized to validate structures and characterize thermal properties of the novel multifunctional quaternary ammonium salts synthesized. The potential adhesive, coupling and antimicrobial properties of these multifunctional monomers encourage their further comprehensive evaluation in conventional and experimental copolymers and composites.
Topics: Anti-Bacterial Agents; Methacrylates; Polymerization; Quaternary Ammonium Compounds
PubMed: 31013893
DOI: 10.3390/molecules24081464 -
Journal of Visualized Experiments : JoVE Jan 2015Streams such as urine and manure can contain high levels of ammonium, which could be recovered for reuse in agriculture or chemistry. The extraction of ammonium from an...
Streams such as urine and manure can contain high levels of ammonium, which could be recovered for reuse in agriculture or chemistry. The extraction of ammonium from an ammonium-rich stream is demonstrated using an electrochemical and a bioelectrochemical system. Both systems are controlled by a potentiostat to either fix the current (for the electrochemical cell) or fix the potential of the working electrode (for the bioelectrochemical cell). In the bioelectrochemical cell, electroactive bacteria catalyze the anodic reaction, whereas in the electrochemical cell the potentiostat applies a higher voltage to produce a current. The current and consequent restoration of the charge balance across the cell allow the transport of cations, such as ammonium, across a cation exchange membrane from the anolyte to the catholyte. The high pH of the catholyte leads to formation of ammonia, which can be stripped from the medium and captured in an acid solution, thus enabling the recovery of a valuable nutrient. The flux of ammonium across the membrane is characterized at different anolyte ammonium concentrations and currents for both the abiotic and biotic reactor systems. Both systems are compared based on current and removal efficiencies for ammonium, as well as the energy input required to drive ammonium transfer across the cation exchange membrane. Finally, a comparative analysis considering key aspects such as reliability, electrode cost, and rate is made. This video article and protocol provide the necessary information to conduct electrochemical and bioelectrochemical ammonia recovery experiments. The reactor setup for the two cases is explained, as well as the reactor operation. We elaborate on data analysis for both reactor types and on the advantages and disadvantages of bioelectrochemical and electrochemical systems.
Topics: Ammonium Compounds; Electrochemical Techniques; Electrodes; Hydrogen-Ion Concentration; Reproducibility of Results; Wastewater
PubMed: 25651406
DOI: 10.3791/52405 -
The Science of the Total Environment Sep 2023Due to the constantly developing road network, a large number of new Motor Rest Area facilities are being built. The aim of the work is a critical assessment of the... (Review)
Review
Due to the constantly developing road network, a large number of new Motor Rest Area facilities are being built. The aim of the work is a critical assessment of the current wastewater management in the MRA and the proposal of appropriate solutions capable of purifying wastewater. The analysis of the current state of the MRA facilities was carried out on the basis of maps, own observations and an assessment of interest in the subject recently by reviewing publication resources. For this purpose, analyzes of the frequency of occurrence of keywords describing the issue were used. The solutions used so far are ineffective. This is mainly due to the perception of wastewater produced in MRA facilities as domestic wastewater. This assumption leads to the selection of inappropriate solutions, which in the long run can lead to an ecological disaster by introducing untreated sewage into the environment. The authors point to the possibility of introducing a circular economy in these places to relieve their environmental impact. Since, wastewater generated in MRA facilities, due to its specificity, is very difficult to treat. They are characterized by uneven inflow, a lack of organic matter, a low C:N ratio and very high concentration of ammonium nitrogen. Conventional activated sludge methods cannot cope with this. The need for changes and the use of solutions suitable for the treatment of wastewater with a high content of ammonium nitrogen has been demonstrated. The authors presented solutions that have the potential to be used in MRA facilities. The application of the proposed solutions from that moment will undoubtedly change the impact of MRA facilities on the environment and solve the problem of wastewater management on a large scale. There is still a lack of research on this thematic scope, which is a challenge authors have taken up.
Topics: Wastewater; Waste Disposal, Fluid; Sewage; Nitrogen; Ammonium Compounds; Bioreactors
PubMed: 37207769
DOI: 10.1016/j.scitotenv.2023.164085