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Nature Chemistry Jul 2020Performing radical polymerizations under ambient conditions is a major challenge because molecular oxygen is an effective radical quencher. Here we show that the...
Performing radical polymerizations under ambient conditions is a major challenge because molecular oxygen is an effective radical quencher. Here we show that the facultative electrogen Shewanella oneidensis can control metal-catalysed living radical polymerizations under apparent aerobic conditions by first consuming dissolved oxygen via aerobic respiration, and then directing extracellular electron flux to a metal catalyst. In both open and closed containers, S. oneidensis enabled living radical polymerizations without requiring the preremoval of oxygen. Polymerization activity was closely tied to S. oneidensis anaerobic metabolism through specific extracellular electron transfer proteins and was effective for a variety of monomers using low (parts per million) concentrations of metal catalysts. Finally, polymerizations survived repeated challenges of oxygen exposure and could be initiated using lyophilized or spent (recycled) cells. Overall, our results demonstrate how the unique ability of S. oneidensis to use both oxygen and metals as respiratory electron acceptors can be leveraged to address salient challenges in polymer synthesis.
Topics: Aerobiosis; Bacterial Proteins; Catalysis; Electron Transport; Free Radicals; Metals; Oxygen; Polymerization; Polymers; Shewanella
PubMed: 32424254
DOI: 10.1038/s41557-020-0460-1 -
Archaea (Vancouver, B.C.) 2018Landfill leachate contains a large amount of organic matter and ammoniacal nitrogen. As such, it has become a complex and difficult issue within the water treatment... (Review)
Review
Landfill leachate contains a large amount of organic matter and ammoniacal nitrogen. As such, it has become a complex and difficult issue within the water treatment industry. The activated sludge process has been found to be a good solution with low processing costs and is now therefore the core process for leachate treatment, especially for nitrogen removal. This paper describes the characteristics and treatment of leachate. Treatment of leachate using the activated sludge process includes the removal of organic matter, ammoniacal nitrogen, and total nitrogen (TN). The core method for the removal of organic matter involves anaerobic treatment supplemented with an aerobic process. Ammoniacal nitrogen is commonly removed using a conventional aerobic treatment, and advanced TN removal is achieved using endogenous denitrification or an anaerobic ammonium oxidation (ANAMMOX) process. Since biological processes are the most economical method for TN removal, a key issue is how to tap the full potential of the activated sludge process and improve TN removal from leachate. This complex issue has been identified as the focus of current scholars, as well as an important future direction for leachate research and development.
Topics: Aerobiosis; Anaerobiosis; Biotechnology; Nitrogen; Organic Chemicals; Sewage; Water Pollutants; Water Pollutants, Chemical; Water Purification
PubMed: 30254508
DOI: 10.1155/2018/1039453 -
Simultaneous Anaerobic and Aerobic Ammonia and Methane Oxidation under Oxygen Limitation Conditions.Applied and Environmental Microbiology Jun 2021Methane and ammonia have to be removed from wastewater treatment effluent in order to discharge it to receiving water bodies. A potential solution for this is a...
Methane and ammonia have to be removed from wastewater treatment effluent in order to discharge it to receiving water bodies. A potential solution for this is a combination of simultaneous ammonia and methane oxidation by anaerobic ammonia oxidation (anammox) bacteria and nitrite/nitrate-dependent anaerobic methane oxidation (N-damo) microorganisms. When applied, these microorganisms will be exposed to oxygen, but little is known about the effect of a low concentration of oxygen on a culture containing these microorganisms. In this study, a stable coculture containing anammox and N-damo microorganisms in a laboratory scale bioreactor was established under oxygen limitation. Membrane inlet mass spectrometry (MIMS) was used to directly measure the simultaneous activity of N-damo, anammox, and aerobic ammonia-oxidizing microorganisms. In addition, batch tests revealed that the bioreactor also harbored aerobic methanotrophs and anaerobic methanogens. Together with fluorescence hybridization (FISH) analysis and metagenomics, these results indicate that the combination of N-damo and anammox activity under the continuous supply of limiting oxygen concentrations is feasible and can be implemented for the removal of methane and ammonia from anaerobic digester effluents. Nitrogen in wastewater leads to eutrophication of the receiving water bodies, and methane is a potent greenhouse gas; it is therefore important that these are removed from wastewater. A potential solution for the simultaneous removal of nitrogenous compounds and methane is the application of a combination of nitrite/nitrate-dependent methane oxidation (N-damo) and anaerobic ammonia oxidation (annamox). In order to do so, it is important to investigate the effect of oxygen on these two anaerobic processes. In this study, we investigate the effect of a continuous oxygen supply on the activity of an anaerobic methane- and ammonia-oxidizing coculture. The findings presented in this study are important for the potential application of these two microbial processes in wastewater treatment.
Topics: Aerobiosis; Ammonia; Anaerobiosis; Archaea; Bacteria; Bioreactors; Methane; Oxidation-Reduction; Oxygen; Water Pollutants, Chemical; Water Purification
PubMed: 33893122
DOI: 10.1128/AEM.00043-21 -
Applied and Environmental Microbiology Mar 2018Purple prairie clover (PPC; Vent.) containing 84.5 g/kg dry matter (DM) of condensed tannin (CT) was ensiled without (control) or with polyethylene glycol (PEG) for 76...
Purple prairie clover (PPC; Vent.) containing 84.5 g/kg dry matter (DM) of condensed tannin (CT) was ensiled without (control) or with polyethylene glycol (PEG) for 76 days, followed by 14 days of aerobic exposure. Changes in fermentation characteristics were determined, and the composition of bacterial and fungal communities were assessed using metagenomic sequencing. The addition of polyethylene glycol (PEG) that deactivated CT at ensiling increased ( < 0.05 to ∼0.001) soluble N, nonprotein N, lactic acid, total volatile fatty acids, ammonia N, deoxynivalenol (DON), and ochratoxin A (OTA) but decreased ( < 0.001) pH and water-soluble carbohydrates. The concentrations of DON and OTA increased ( < 0.001) for both silages, with the extent of increase being greater for control than for PEG-treated silage during aerobic exposure. The PEG-treated silage exhibited higher ( < 0.01 to ∼0.001) copy numbers of total bacteria, , yeasts, and fungi than the control. The addition of PEG decreased ( < 0.01) bacterial diversity during both ensiling and aerobic exposure, whereas it increased ( < 0.05) fungal diversity during aerobic exposure. The addition of PEG at ensiling increased ( < 0.05) the abundances of and species but decreased ( < 0.01) the abundances of and species. Filamentous fungi were found in the microbiome at ensiling and after aerobic exposure, whereas spp. were the dominate bacteria after aerobic exposure. In conclusion, CT decreased protein degradation and improved the aerobic stability of silage. These desirable outcomes likely reflect the ability of PPC CT to inhibit those microorganisms involved in lowering silage quality and in the production of mycotoxins. The present study reports the effects of condensed tannins on the complex microbial communities involved in ensiling and aerobic exposure of purple prairie clover. This study documents the ability of condensed tannins to lower mycotoxin production and the associated microbiome. Taxonomic bacterial community profiles were dominated by after fermentation, with a notable increase in spp. as a result of aerobic exposure. It is interesting to observe that condensed tannins decreased bacterial diversity during both ensiling and aerobic exposure but increased fungal diversity during aerobic exposure only. The present study indicates that the effects of condensed tannins on microbial communities lead to reduced lactic acid and total volatile fatty acid production, proteolysis, and mycotoxin concentration in the terminal silage and improved aerobic stability. Condensed tannins could be used as an additive to control unfavorable microbial development and maybe enhanced feed safety.
Topics: Aerobiosis; Bacteria; Fermentation; Fungi; Mycobiome; Mycotoxins; Proanthocyanidins; Silage
PubMed: 29247054
DOI: 10.1128/AEM.02274-17 -
Journal of Physiology and Pharmacology... Jun 2018Currently, literature has accumulated great knowledge over the effect of exercise on the neurotrophin named brain derived neurotrophic factor (BDNF) and its role in... (Review)
Review
Currently, literature has accumulated great knowledge over the effect of exercise on the neurotrophin named brain derived neurotrophic factor (BDNF) and its role in neuronal plasticity. However, there is no enough discussion about how the exercise is related to enrichment of BDNF in specific metabolic properties. This review provides the current evidences regarding aerobic metabolism relation to BDNF concentrations in healthy individuals. A PICOS strategy was applied considering the mesh terms for: P - healthy subjects; I - physical exercise; C - aerobic metabolism demands; O - BDNF concentrations; S - before and after aerobic exercise; on PubMed, Scopus and Medline databases. Studies presenting at least one session the exercise with reports of BDNF analysis before and after were included. Reviews, letters, case-reports, articles not written in English, non- published or involving non-healthy populations were excluded. Compiling results, it was possible to observe a close interaction between different aerobic energy demands from the exercise models and the responses of BDNF, suggesting thus that increases in BDNF concentrations are associated to the amount of aerobic energy required by exercise in a dose-dependent manner. Moreover, the dynamics of BDNF synthesis and reuptake resemble the functioning of the metabolic systems of aerobic energy generation, with which they share a co-transcriptional factor dependence.
Topics: Aerobiosis; Brain; Brain-Derived Neurotrophic Factor; Exercise; Humans; Neuronal Plasticity
PubMed: 30342429
DOI: 10.26402/jpp.2018.3.12 -
Water Research Nov 2020The settling behavior of aerobic granular sludge (AGS) in full-scale reactors is different from the settling of normal activated sludge. Current activated sludge models...
The settling behavior of aerobic granular sludge (AGS) in full-scale reactors is different from the settling of normal activated sludge. Current activated sludge models lack the features to describe the segregation of granules based on size during the settling process. This segregation plays an important role in the granulation process and therefore a better understanding of the settling is essential. The goal of this study was to model and evaluate the segregation of different granule sizes during settling and feeding in full-scale aerobic granular sludge reactors. Hereto the Patwardhan and Tien model was used. This model is an implementation of the Richardson and Zaki model, allowing for multiple classes of particles. To create the granular settling model, the most relevant parameters were identified using aerobic granular sludge from different full-scale Nereda® reactors. The settling properties of individual granules were measured as was the bulk behavior of granular sludge beds with uniform granular sludge particles. The obtained parameters were combined in a model containing multiple granule classes, which then was validated for granular sludge settling in a full-scale Nereda® reactor. In practice a hydraulic selection pressure is used to select for granular sludge. Under the same hydraulic selection pressure the model predicted that different stable granular size distributions can occur. This indicates that granular size distribution control would need a different mechanism then the hydraulic selection pressure alone. This model can be used to better understand and optimize operational parameters of AGS reactors that depend on granular sludge size, like biological nutrient removal. Furthermore insights from this model can also be used in the development of continuously fed AGS systems.
Topics: Aerobiosis; Bioreactors; Sewage; Waste Disposal, Fluid
PubMed: 32891906
DOI: 10.1016/j.watres.2020.116135 -
Biochimica Et Biophysica Acta Mar 2016Aerobic respiratory chains from all life kingdoms are composed by several complexes that have been deeply characterized in their isolated form. These membranous... (Review)
Review
Aerobic respiratory chains from all life kingdoms are composed by several complexes that have been deeply characterized in their isolated form. These membranous complexes link the oxidation of reducing substrates to the reduction of molecular oxygen, in a process that conserves energy by ion translocation between both sides of the mitochondrial or prokaryotic cytoplasmatic membranes. In recent years there has been increasing evidence that those complexes are organized as supramolecular structures, the so-called supercomplexes and respirasomes, being available for eukaryotes strong data namely obtained by electron microscopy and single particle analysis. A parallel study has been developed for prokaryotes, based on blue native gels and mass spectrometry analysis, showing that in these more simple unicellular organisms such supercomplexes also exist, involving not only typical aerobic-respiration associated complexes, but also anaerobic-linked enzymes. After a short overview of the data on eukaryotic supercomplexes, we will analyse comprehensively the different types of prokaryotic aerobic respiratory supercomplexes that have been thus far suggested, in both bacteria and archaea. This article is part of a Special Issue entitled Organization and dynamics of bioenergetic systems in bacteria, edited by Prof Conrad Mullineaux.
Topics: Aerobiosis; Bacteria; Bacterial Proteins; Cell Membrane; Electron Transport; Electron Transport Chain Complex Proteins; Proton-Motive Force
PubMed: 26546715
DOI: 10.1016/j.bbabio.2015.11.001 -
MBio Mar 2016Steroids are ubiquitous in natural environments and are a significant growth substrate for microorganisms. Microbial steroid metabolism is also important for some... (Comparative Study)
Comparative Study
UNLABELLED
Steroids are ubiquitous in natural environments and are a significant growth substrate for microorganisms. Microbial steroid metabolism is also important for some pathogens and for biotechnical applications. This study delineated the distribution of aerobic steroid catabolism pathways among over 8,000 microorganisms whose genomes are available in the NCBI RefSeq database. Combined analysis of bacterial, archaeal, and fungal genomes with both hidden Markov models and reciprocal BLAST identified 265 putative steroid degraders within only Actinobacteria and Proteobacteria, which mainly originated from soil, eukaryotic host, and aquatic environments. These bacteria include members of 17 genera not previously known to contain steroid degraders. A pathway for cholesterol degradation was conserved in many actinobacterial genera, particularly in members of the Corynebacterineae, and a pathway for cholate degradation was conserved in members of the genus Rhodococcus. A pathway for testosterone and, sometimes, cholate degradation had a patchy distribution among Proteobacteria. The steroid degradation genes tended to occur within large gene clusters. Growth experiments confirmed bioinformatic predictions of steroid metabolism capacity in nine bacterial strains. The results indicate there was a single ancestral 9,10-seco-steroid degradation pathway. Gene duplication, likely in a progenitor of Rhodococcus, later gave rise to a cholate degradation pathway. Proteobacteria and additional Actinobacteria subsequently obtained a cholate degradation pathway via horizontal gene transfer, in some cases facilitated by plasmids. Catabolism of steroids appears to be an important component of the ecological niches of broad groups of Actinobacteria and individual species of Proteobacteria.
IMPORTANCE
Steroids are ubiquitous growth substrates for environmental and pathogenic bacteria, and bacterial steroid metabolism has important pharmaceutical and health applications. To date, the genetics and biochemistry of microbial steroid degradation have mainly been studied in a few model bacteria, and the diversity of this metabolism remains largely unexplored. Here, we provide a bioinformatically derived perspective of the taxonomic distribution of aerobic microbial steroid catabolism pathways. We identified several novel steroid-degrading bacterial groups, including ones from marine environments. In several cases, we confirmed bioinformatic predictions of metabolism in cultures. We found that cholesterol and cholate catabolism pathways are highly conserved among certain actinobacterial taxa. We found evidence for horizontal transfer of a pathway to several proteobacterial genera, conferring testosterone and, sometimes, cholate catabolism. The results of this study greatly expand our ecological and evolutionary understanding of microbial steroid metabolism and provide a basis for better exploiting this metabolism for biotechnology.
Topics: Actinobacteria; Aerobiosis; Biotransformation; Genomics; Metabolic Networks and Pathways; Proteobacteria; Steroids
PubMed: 26956583
DOI: 10.1128/mBio.00166-16 -
Frontiers in Immunology 2018Dendritic cell (DC) activation is characterized by an acute increase in glucose metabolic flux that is required to fuel the high anabolic rates associated with DC... (Review)
Review
Dendritic cell (DC) activation is characterized by an acute increase in glucose metabolic flux that is required to fuel the high anabolic rates associated with DC activation. Inhibition of glycolysis significantly attenuates most aspects of DC immune effector function including antigen presentation, inflammatory cytokine production, and T cell stimulatory capacity. The cellular nutrient sensor mammalian/mechanistic Target of Rapamycin (mTOR) is an important upstream regulator of glycolytic metabolism and plays a central role in coordinating DC metabolic changes and immune responses. Because mTOR signaling can be activated by a variety of immunological stimuli, including signaling through the Toll-like Receptor (TLR) family of receptors, mTOR is involved in orchestrating many aspects of the DC metabolic response to microbial stimuli. It has become increasingly clear that mTOR's role in promoting or attenuating inflammatory processes in DCs is highly context-dependent and varies according to specific cellular subsets and the immunological conditions being studied. This review will address key aspects of the complex role of mTOR in regulating DC metabolism and effector function.
Topics: Aerobiosis; Animals; Autophagy; Cell Survival; Dendritic Cells; Energy Metabolism; Glycolysis; Humans; Immunomodulation; Nutritional Physiological Phenomena; Signal Transduction; TOR Serine-Threonine Kinases
PubMed: 30692999
DOI: 10.3389/fimmu.2018.03145 -
Proceedings of the National Academy of... Sep 2022Aerobic life is powered by membrane-bound enzymes that catalyze the transfer of electrons to oxygen and protons across a biological membrane. Cytochrome oxidase (CO)...
Aerobic life is powered by membrane-bound enzymes that catalyze the transfer of electrons to oxygen and protons across a biological membrane. Cytochrome oxidase (CO) functions as a terminal electron acceptor in mitochondrial and bacterial respiratory chains, driving cellular respiration and transducing the free energy from O reduction into proton pumping. Here we show that CO creates orientated electric fields around a nonpolar cavity next to the active site, establishing a molecular switch that directs the protons along distinct pathways. By combining large-scale quantum chemical density functional theory (DFT) calculations with hybrid quantum mechanics/molecular mechanics (QM/MM) simulations and atomistic molecular dynamics (MD) explorations, we find that reduction of the electron donor, heme , leads to dissociation of an arginine (Arg438)-heme D-propionate ion-pair. This ion-pair dissociation creates a strong electric field of up to 1 V Å along a water-mediated proton array leading to a transient proton loading site (PLS) near the active site. Protonation of the PLS triggers the reduction of the active site, which in turn aligns the electric field vectors along a second, "chemical," proton pathway. We find a linear energy relationship of the proton transfer barrier with the electric field strength that explains the effectivity of the gating process. Our mechanism shows distinct similarities to principles also found in other energy-converting enzymes, suggesting that orientated electric fields generally control enzyme catalysis.
Topics: Aerobiosis; Electron Transport; Electron Transport Complex IV; Oxygen; Protons; Water
PubMed: 36095184
DOI: 10.1073/pnas.2207761119