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1.
Nat Commun ; 12(1): 2008, 2021 03 31.
Artigo em Inglês | MEDLINE | ID: mdl-33790295

RESUMO

Despite the tremendous progress of coupling organic electrooxidation with hydrogen generation in a hybrid electrolysis, electroreforming of raw biomass coupled to green hydrogen generation has not been reported yet due to the rigid polymeric structures of raw biomass. Herein, we electrooxidize the most abundant natural amino biopolymer chitin to acetate with over 90% yield in hybrid electrolysis. The overall energy consumption of electrolysis can be reduced by 15% due to the thermodynamically and kinetically more favorable chitin oxidation over water oxidation. In obvious contrast to small organics as the anodic reactant, the abundance of chitin endows the new oxidation reaction excellent scalability. A solar-driven electroreforming of chitin and chitin-containing shrimp shell waste is coupled to safe green hydrogen production thanks to the liquid anodic product and suppression of oxygen evolution. Our work thus demonstrates a scalable and safe process for resource upcycling and green hydrogen production for a sustainable energy future.


Assuntos
Acetatos/química , Quitina/química , Eletrólise/métodos , Hidrogênio/química , Energia Renovável , Acetatos/metabolismo , Biomassa , Quitina/metabolismo , Eletrodos , Eletrólise/instrumentação , Hidrogênio/metabolismo , Modelos Químicos , Estrutura Molecular , Oxirredução , Espectroscopia de Prótons por Ressonância Magnética , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por Matriz
2.
Georgian Med News ; (311): 156-162, 2021 Feb.
Artigo em Russo | MEDLINE | ID: mdl-33814411

RESUMO

Objective - to find out the possibility of using molecular hydrogen in the correction of no-reflow syndrome in the polyuric stage of acute kidney injury 72 hours after the administration of mercuric chloride in rats on a hyposodium diet. The experiments were performed on 60 male white non-linear sexually mature rats weighing 0.16-0.18 kg to study the effect of water loading with saturation with molecular hydrogen. Sublimate nephropathy was modeled under conditions of a hyposodium diet by subcutaneous injection of 0.1% mercury dichloride solution at a dosage of 5 mg/kg with a study after 72 hours, which corresponded to the early polyuric stage of acute kidney injury and the development of no-reflow syndrome. To saturate the water with molecular hydrogen at a concentration of 1.2 ppm and a redox potential from -100 to -350 mV, a new generation H2 generator Blue Water 900 (Korea) was used, containing an improved proton-exchange membrane PEM/SPE. Used: pathophysiological, biochemical, functional, chemiluminescent, statistical research methods. The antioxidant effect of loading with water with saturation with molecular hydrogen leads to a decrease in the loss of sodium ions due to an improvement in its reabsorption and ß2-microglobulin in the proximal tubule, a decrease in lipid peroxidation in the renal cortex was noted, the degree of its damage by an increase in the K+/Na+ ratio and a decrease in degree of edema. Improvement in the condition of the proximal nephron led to an increase in total, enzymatic fibrinolytic activity in the renal cortex. The increase in the activity of succinate dehydrogenase in the renal cortex is due to an increase in the delivery of electrons due to the negative redox potential and the selective antioxidant effect of molecular hydrogen. The anti-edema effect of molecular hydrogen was revealed at the level of 7 layers of the kidney. During the formation of the no-reflow syndrome in rats on a low-sodium diet 72 hours after the introduction of mercuric chloride, the possibility of breaking large and small vicious circles with an antioxidant solution of H2 was shown due to its high permeability and the ability to neutralize the hydroxyl radical and peroxynitrite.


Assuntos
Lesão Renal Aguda , Cloreto de Mercúrio , Lesão Renal Aguda/induzido quimicamente , Lesão Renal Aguda/tratamento farmacológico , Lesão Renal Aguda/metabolismo , Animais , Hidrogênio/metabolismo , Rim/metabolismo , Peroxidação de Lipídeos , Masculino , Ratos
3.
Proc Natl Acad Sci U S A ; 118(2)2021 01 12.
Artigo em Inglês | MEDLINE | ID: mdl-33419920

RESUMO

Life in environments devoid of photosynthesis, such as on early Earth or in contemporary dark subsurface ecosystems, is supported by chemical energy. How, when, and where chemical nutrients released from the geosphere fuel chemosynthetic biospheres is fundamental to understanding the distribution and diversity of life, both today and in the geologic past. Hydrogen (H2) is a potent reductant that can be generated when water interacts with reactive components of mineral surfaces such as silicate radicals and ferrous iron. Such reactive mineral surfaces are continually generated by physical comminution of bedrock by glaciers. Here, we show that dissolved H2 concentrations in meltwaters from an iron and silicate mineral-rich basaltic glacial catchment were an order of magnitude higher than those from a carbonate-dominated catchment. Consistent with higher H2 abundance, sediment microbial communities from the basaltic catchment exhibited significantly shorter lag times and faster rates of net H2 oxidation and dark carbon dioxide (CO2) fixation than those from the carbonate catchment, indicating adaptation to use H2 as a reductant in basaltic catchments. An enrichment culture of basaltic sediments provided with H2, CO2, and ferric iron produced a chemolithoautotrophic population related to Rhodoferax ferrireducens with a metabolism previously thought to be restricted to (hyper)thermophiles and acidophiles. These findings point to the importance of physical and chemical weathering processes in generating nutrients that support chemosynthetic primary production. Furthermore, they show that differences in bedrock mineral composition can influence the supplies of nutrients like H2 and, in turn, the diversity, abundance, and activity of microbial inhabitants.


Assuntos
Ecossistema , Fenômenos Geológicos , Hidrogênio/metabolismo , Camada de Gelo/microbiologia , Ciclo do Carbono , Dióxido de Carbono/metabolismo , Islândia , Metagenoma , Oxirredução
4.
Nat Microbiol ; 6(2): 246-256, 2021 02.
Artigo em Inglês | MEDLINE | ID: mdl-33398096

RESUMO

Soil microorganisms globally are thought to be sustained primarily by organic carbon sources. Certain bacteria also consume inorganic energy sources such as trace gases, but they are presumed to be rare community members, except within some oligotrophic soils. Here we combined metagenomic, biogeochemical and modelling approaches to determine how soil microbial communities meet energy and carbon needs. Analysis of 40 metagenomes and 757 derived genomes indicated that over 70% of soil bacterial taxa encode enzymes to consume inorganic energy sources. Bacteria from 19 phyla encoded enzymes to use the trace gases hydrogen and carbon monoxide as supplemental electron donors for aerobic respiration. In addition, we identified a fourth phylum (Gemmatimonadota) potentially capable of aerobic methanotrophy. Consistent with the metagenomic profiling, communities within soil profiles from diverse habitats rapidly oxidized hydrogen, carbon monoxide and to a lesser extent methane below atmospheric concentrations. Thermodynamic modelling indicated that the power generated by oxidation of these three gases is sufficient to meet the maintenance needs of the bacterial cells capable of consuming them. Diverse bacteria also encode enzymes to use trace gases as electron donors to support carbon fixation. Altogether, these findings indicate that trace gas oxidation confers a major selective advantage in soil ecosystems, where availability of preferred organic substrates limits microbial growth. The observation that inorganic energy sources may sustain most soil bacteria also has broad implications for understanding atmospheric chemistry and microbial biodiversity in a changing world.


Assuntos
Bactérias/enzimologia , Monóxido de Carbono/metabolismo , Hidrogênio/metabolismo , Microbiota , Microbiologia do Solo , Solo , Bactérias/classificação , Bactérias/genética , Metagenômica , Oxirredução , Filogenia
5.
BMC Bioinformatics ; 22(1): 3, 2021 Jan 06.
Artigo em Inglês | MEDLINE | ID: mdl-33407079

RESUMO

BACKGROUND: Hydrogen cross-feeding microbes form a functionally important subset of the human colonic microbiota. The three major hydrogenotrophic functional groups of the colon: sulphate-reducing bacteria (SRB), methanogens and reductive acetogens, have been linked to wide ranging impacts on host physiology, health and wellbeing. RESULTS: An existing mathematical model for microbial community growth and metabolism was combined with models for each of the three hydrogenotrophic functional groups. The model was further developed for application to the colonic environment via inclusion of responsive pH, host metabolite absorption and the inclusion of host mucins. Predictions of the model, using two existing metabolic parameter sets, were compared to experimental faecal culture datasets. Model accuracy varied between experiments and measured variables and was most successful in predicting the growth of high relative abundance functional groups, such as the Bacteroides, and short chain fatty acid (SCFA) production. Two versions of the colonic model were developed: one representing the colon with sequential compartments and one utilising a continuous spatial representation. When applied to the colonic environment, the model predicted pH dynamics within the ranges measured in vivo and SCFA ratios comparable to those in the literature. The continuous version of the model simulated relative abundances of microbial functional groups comparable to measured values, but predictions were sensitive to the metabolic parameter values used for each functional group. Sulphate availability was found to strongly influence hydrogenotroph activity in the continuous version of the model, correlating positively with SRB and sulphide concentration and negatively with methanogen concentration, but had no effect in the compartmentalised model version. CONCLUSIONS: Although the model predictions compared well to only some experimental measurements, the important features of the colon environment included make it a novel and useful contribution to modelling the colonic microbiota.


Assuntos
Bactérias/metabolismo , Colo , Microbioma Gastrointestinal , Hidrogênio/metabolismo , Colo/metabolismo , Colo/microbiologia , Humanos , Modelos Biológicos , Sulfetos/metabolismo
6.
Arch Pharm (Weinheim) ; 354(4): e2000378, 2021 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-33368699

RESUMO

Many diseases as well as acute conditions can lead to fatigue, which can be either temporary or chronic in nature. Acute fatigue develops frequently after physical exercise or after alcohol hangover, whereas microbial infections such as influenza or COVID-19 and chronic diseases like Parkinson's disease or multiple sclerosis are often associated with chronic fatigue. Oxidative stress and a resulting disturbance of mitochondrial function are likely to be common denominators for many forms of fatigue, and antioxidant treatments have been shown to be effective in alleviating the symptoms of fatigue. In this study, we review the role of reactive oxygen and nitrogen species in fatigue and the antioxidant effects of the intake of molecular hydrogen. We propose that molecular hydrogen is well suited for the treatment of temporary and chronic forms of oxidative stress-associated fatigue.


Assuntos
Fadiga , Hidrogênio , Estresse Oxidativo , Antioxidantes/metabolismo , Antioxidantes/farmacologia , /fisiopatologia , Fadiga/etiologia , Fadiga/metabolismo , Fadiga/terapia , Humanos , Hidrogênio/metabolismo , Hidrogênio/farmacologia , Nitrogênio , Estresse Oxidativo/efeitos dos fármacos , Estresse Oxidativo/fisiologia , Relação Quantitativa Estrutura-Atividade , Espécies Reativas de Oxigênio
7.
Chemosphere ; 262: 128213, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33182078

RESUMO

Although phosphine is ubiquitously present in anaerobic environments, little is known regarding the microbial community dynamics and metabolic pathways associated with phosphine formation in an anaerobic digestion system. This study investigated the production of phosphine in anaerobic digestion, with results indicating that phosphine production mainly occurred during logarithmic microbial growth. Dehydrogenase and hydrogen promoted the production of phosphine, with a maximum phosphine concentration of 300 mg/m3. The abundance of Ruminococcaceae and Escherichia was observed to promote phosphine generation. The analysis of metabolic pathways based on the Kyoto Encyclopedia of Genes and Genomes (KEGG) and the MetaCyc pathway database revealed the highest relative abundance of replication and repair in genetic information processing; further, the cofactor, prosthetic group, electron carrier, and vitamin biosynthesis were observed to be closely related to phosphine formation. A phylogenetic tree was reconstructed based on the neighbor-joining method. The results indicated the clear evolutionary position of the isolated Pseudescherichia sp. SFM4 strain, adjacent to Escherichia, with a stable phosphate-reducing ability for a maximum phosphine concentration of 26 mg/m3. The response surface experiment indicated that the initial optimal conditions for phosphine production by SFM4 could be achieved with nitrogen, carbon, and phosphorus loads of 6.17, 300, and 10 mg/L, respectively, at pH 7.47. These results provide comprehensive insights into the dynamic changes in the microbial structure, isolated single bacterial strain, and metabolic pathways associated with phosphine formation. They also provide information on the molecular biology associated with phosphorus recycling.


Assuntos
Reatores Biológicos/microbiologia , Clostridiales/metabolismo , Escherichia/metabolismo , Redes e Vias Metabólicas , Microbiota , Fosfinas/análise , Anaerobiose , Clostridiales/genética , Escherichia/genética , Hidrogênio/metabolismo , Redes e Vias Metabólicas/genética , Nitrogênio/metabolismo , Fosfatos/metabolismo , Fosfinas/metabolismo , Fósforo/metabolismo , Filogenia , Esgotos/microbiologia
8.
Life Sci ; 267: 118945, 2021 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-33359745

RESUMO

AIMS: Oxidized phospholipids (OxPLs) are formed as a result of oxidative stress, which potentially mediate multiple pathological effects. We aimed to evaluate the effects of hydrogen (H2) on OxPLs in vivo and the underlying mechanism. MAIN METHODS: Rats were randomly assigned to three groups: control group fed with a chow diet, model group fed with a high-fat diet, and H2-treated group fed with a high-fat diet and treated by 4% H2 inhalation for ten weeks. OxPLs in liver and plasma were analyzed by liquid chromatography-mass spectrometry. High-density lipoprotein (HDL) was separated by ultracentrifugation. A proteomic analysis was performed to reveal the alternation of HDL protein composition and he antioxidant capacity of HDL was tested by low-density lipoprotein oxidation experiment. Furthermore, the activity or expression of HDL-associated enzymes were evaluated. KEY FINDINGS: Inhalation of 4% H2 decreased the accumulation of OxPLs in rats. In vitro tests revealed that the different concentrations of H2 did not inhibit the formation of OxPLs mediated by non-enzymatic oxidation. H2 inhalation altered the components and enhanced the anti-oxidative capacity of HDL in rats fed with a high-fat diet. Further experiments showed that H2 significantly regulated the activity of lipoprotein-associated phospholipase A2, paraoxonase-1, and the expression of lecithin:cholesterol acyltransferase. SIGNIFICANCE: Our findings revealed that H2 may reduce the OxPLs levels through its influence on HDL-associated enzymes that can act on OxPLs, suggesting that H2 can be used in alleviating diseases related to lipid peroxidation due to oxidative stress.


Assuntos
Hidrogênio/metabolismo , Hidrogênio/farmacologia , Fosfolipídeos/metabolismo , Administração por Inalação , Animais , Antioxidantes/farmacologia , Apolipoproteína A-I/metabolismo , HDL-Colesterol/efeitos dos fármacos , HDL-Colesterol/metabolismo , Cromatografia Líquida/métodos , Dieta Hiperlipídica/efeitos adversos , Peroxidação de Lipídeos , Lipoproteínas HDL/efeitos dos fármacos , Lipoproteínas HDL/metabolismo , Lipoproteínas LDL/efeitos dos fármacos , Lipoproteínas LDL/metabolismo , Fígado/metabolismo , Masculino , Oxirredução/efeitos dos fármacos , Estresse Oxidativo/efeitos dos fármacos , Fosfatidilcolina-Esterol O-Aciltransferase/metabolismo , Proteômica/métodos , Ratos , Ratos Sprague-Dawley
9.
Nat Commun ; 11(1): 5448, 2020 10 28.
Artigo em Inglês | MEDLINE | ID: mdl-33116131

RESUMO

Compartmentalization is a ubiquitous building principle in cells, which permits segregation of biological elements and reactions. The carboxysome is a specialized bacterial organelle that encapsulates enzymes into a virus-like protein shell and plays essential roles in photosynthetic carbon fixation. The naturally designed architecture, semi-permeability, and catalytic improvement of carboxysomes have inspired rational design and engineering of new nanomaterials to incorporate desired enzymes into the protein shell for enhanced catalytic performance. Here, we build large, intact carboxysome shells (over 90 nm in diameter) in the industrial microorganism Escherichia coli by expressing a set of carboxysome protein-encoding genes. We develop strategies for enzyme activation, shell self-assembly, and cargo encapsulation to construct a robust nanoreactor that incorporates catalytically active [FeFe]-hydrogenases and functional partners within the empty shell for the production of hydrogen. We show that shell encapsulation and the internal microenvironment of the new catalyst facilitate hydrogen production of the encapsulated oxygen-sensitive hydrogenases. The study provides insights into the assembly and formation of carboxysomes and paves the way for engineering carboxysome shell-based nanoreactors to recruit specific enzymes for diverse catalytic reactions.


Assuntos
Proteínas de Bactérias/metabolismo , Reatores Biológicos , Hidrogênio/metabolismo , Organelas/metabolismo , Proteínas de Bactérias/genética , Biocatálise , Bioengenharia , Reatores Biológicos/microbiologia , Escherichia coli/genética , Escherichia coli/metabolismo , Genes Bacterianos , Halothiobacillus/genética , Halothiobacillus/metabolismo , Hidrogenase/metabolismo , Proteínas com Ferro-Enxofre/metabolismo , Nanocápsulas/química , Nanocápsulas/ultraestrutura , Organelas/genética , Organelas/ultraestrutura , Fotossíntese , Ribulose-Bifosfato Carboxilase/genética , Ribulose-Bifosfato Carboxilase/metabolismo
10.
Ecotoxicol Environ Saf ; 203: 110991, 2020 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-32888602

RESUMO

The stimulant and toxicity effects of reported organic (acetic acid, propionic acid, butyric acid, formic acid, oil & grease) and inorganic (copper) by-products presented in palm oil mill effluent on anaerobic bacterial population were examined in this paper. The toxicity test had shown that acetic, propionic and butyric acids tend to stimulate the bacterial density level (survival rate more than 50%), while formic acid, copper, oil and grease were shown to have suppressed the density level (survival rate less than 50%). The highest biomass recorded was 1.66 mg/L for the concentration of acetic acid at 216 mg/L and lowest biomass concentration, 0.90 mg/L for copper at 1.40 mg/L. Biohydrogen-producing bacteria have a favourable growth rate around pH 5.5. The comparison of half maximal effective concentration (EC50) values between two test duration on the effects of organic and inorganic by-products postulate that bacteria had a higher tolerance towards volatile fatty acids. While acetic, butyric and propionic acids had exhibited higher tolerance EC50 values for bacteria, but the opposite trend was observed for formic acid, copper and oil & grease.


Assuntos
Bactérias Anaeróbias/efeitos dos fármacos , Óleo de Palmeira/toxicidade , Testes de Toxicidade/métodos , Relação Dose-Resposta a Droga , Hidrogênio/metabolismo , Resíduos Industriais/análise
11.
J Dairy Sci ; 103(8): 7124-7140, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32600762

RESUMO

Within the rumen, nitrate can serve as an alternative sink for aqueous hydrogen [H2(aq)] accumulating during fermentation, producing nitrite, which ideally is further reduced to ammonium but can accumulate under conditions not yet explained. Defaunation has also been associated with decreased methanogenesis in meta-analyses because protozoa contribute significantly to H2 production. In the present study, we applied a 2 × 2 factorial treatment arrangement in a 4 × 4 Latin square design to dual-flow continuous culture fermentors (n = 4). Treatments were control without nitrate (-NO3-) versus with nitrate (+NO3-; 1.5% of diet dry matter), factorialized with normal protozoa (faunated, FAUN) versus defaunation (DEF) by decreasing the temperature moderately and changing filters over the first 4 d of incubation. We detected no main effects of DEF or interaction of faunation status with +NO3-. The main effect of +NO3- increased H2(aq) by 11.0 µM (+117%) compared with -NO3-. The main effect of +NO3- also decreased daily CH4 production by 8.17 mmol CH4/d (31%) compared with -NO3-. Because there were no treatment effects on neutral detergent fiber digestibility, the main effect of +NO3- also decreased CH4 production by 1.43 mmol of CH4/g of neutral detergent fiber degraded compared with -NO3-. There were no effects of treatment on other nutrient digestibilities, N flow, or microbial N flow per gram of nutrient digested. The spike in H2(aq) after feeding NO3- provides evidence that methanogenesis is inhibited by substrate access rather than concentration, regardless of defaunation, or by direct inhibition of NO2-. Methanogens were not decreased by defaunation, suggesting a compensatory increase in non-protozoa-associated methanogens or an insignificant contribution of protozoa-associated methanogens. Despite adaptive reduction of NO3- to NH4+ and methane inhibition in continuous culture, practical considerations such as potential to depress dry matter intake and on-farm ration variability should be addressed before considering NO3- as an avenue for greater sustainability of greenhouse gas emissions in US dairy production.


Assuntos
Fibras na Dieta/metabolismo , Eucariotos/metabolismo , Hidrogênio/metabolismo , Metano/metabolismo , Microbiota , Nitratos/farmacologia , Compostos de Amônio/metabolismo , Animais , Bactérias/metabolismo , Reatores Biológicos , Técnicas de Cultura , Dieta/veterinária , Ingestão de Alimentos , Ácidos Graxos Voláteis/metabolismo , Fermentação/efeitos dos fármacos , Hidrogênio/análise , Nitritos/metabolismo , Nitrogênio/metabolismo , Rúmen/metabolismo
12.
Nature ; 584(7819): 69-74, 2020 08.
Artigo em Inglês | MEDLINE | ID: mdl-32512577

RESUMO

Enzymes are increasingly explored for use in asymmetric synthesis1-3, but their applications are generally limited by the reactions available to naturally occurring enzymes. Recently, interest in photocatalysis4 has spurred the discovery of novel reactivity from known enzymes5. However, so far photoinduced enzymatic catalysis6 has not been used for the cross-coupling of two molecules. For example, the intermolecular coupling of alkenes with α-halo carbonyl compounds through a visible-light-induced radical hydroalkylation, which could provide access to important γ-chiral carbonyl compounds, has not yet been achieved by enzymes. The major challenges are the inherent poor photoreactivity of enzymes and the difficulty in achieving stereochemical control of the remote prochiral radical intermediate7. Here we report a visible-light-induced intermolecular radical hydroalkylation of terminal alkenes that does not occur naturally, catalysed by an 'ene' reductase using readily available α-halo carbonyl compounds as reactants. This method provides an efficient approach to the synthesis of various carbonyl compounds bearing a γ-stereocentre with excellent yields and enantioselectivities (up to 99 per cent yield with 99 per cent enantiomeric excess), which otherwise are difficult to access using chemocatalysis. Mechanistic studies suggest that the formation of the complex of the substrates (α-halo carbonyl compounds) and the 'ene' reductase triggers the enantioselective photoinduced radical reaction. Our work further expands the reactivity repertoire of biocatalytic, synthetically useful asymmetric transformations by the merger of photocatalysis and enzyme catalysis.


Assuntos
Alcenos/química , Alcenos/metabolismo , Hidrogênio/química , Hidrogênio/metabolismo , Luz , Oxirredutases/metabolismo , Processos Fotoquímicos/efeitos da radiação , Álcoois/química , Álcoois/metabolismo , Alquilação/efeitos da radiação , Biocatálise/efeitos da radiação , Biomassa , Carboxiliases/metabolismo , Flavinas/metabolismo , Modelos Químicos , Modelos Moleculares , Estereoisomerismo
13.
Appl Environ Microbiol ; 86(17)2020 08 18.
Artigo em Inglês | MEDLINE | ID: mdl-32561585

RESUMO

Hydrogen-entangled electron transfer has been verified as an important extracellular pathway of sharing reducing equivalents to regulate biofilm activities within a diversely anaerobic environment, especially in microbial electrosynthesis systems. However, with a lack of useful methods for in situ hydrogen detection in cathodic biofilms, the role of hydrogen involvement in electron transfer is still debatable. Here, a cathodic biofilm was constructed in CH4-produced microbial electrosynthesis reactors, in which the hydrogen evolution dynamic was analyzed to confirm the presence of hydrogen-associated electron transfer near the cathode within a micrometer scale. Fluorescent in situ hybridization images indicated that a colocalized community of archaea and bacteria developed within a 58.10-µm-thick biofilm at the cathode, suggesting that the hydrogen gradient detected by the microsensor was consumed by the collaboration of bacteria and archaea. Coupling of a microsensor and cyclic voltammetry test further provided semiquantitative results of the hydrogen-associated contribution to methane generation (around 21.20% ± 1.57% at a potential of -0.5 V to -0.69 V). This finding provides deep insight into the mechanism of electron transfer in biofilm on conductive materials.IMPORTANCE Electron transfer from an electrode to biofilm is of great interest to the fields of microbial electrochemical technology, bioremediation, and methanogenesis. It has a promising potential application to boost more value-added products or pollutant degradation. Importantly, the ability of microbes to obtain electrons from electrodes and utilize them brings new insight into direct interspecies electron transfer during methanogenesis. Previous studies verified the direct pathway of electron transfer from the electrode to a pure-culture bacterium, but it was rarely reported how the methanogenic biofilm of mixed cultures shares electrons by a hydrogen-associated or hydrogen-free pathway. In the current study, a combination method of microsensor and cyclic voltammetry successfully semiquantified the role of hydrogen in electron transfer from an electrode to methanogenic biofilm.


Assuntos
Archaea/fisiologia , Fenômenos Fisiológicos Bacterianos , Biofilmes , Hidrogênio/metabolismo , Metano/metabolismo , Archaea/metabolismo , Bactérias/metabolismo , Transporte de Elétrons
14.
Proc Natl Acad Sci U S A ; 117(23): 13168-13175, 2020 06 09.
Artigo em Inglês | MEDLINE | ID: mdl-32471945

RESUMO

Living biological systems display a fascinating ability to self-organize their metabolism. This ability ultimately determines the metabolic robustness that is fundamental to controlling cellular behavior. However, fluctuations in metabolism can affect cellular homeostasis through transient oscillations. For example, yeast cultures exhibit rhythmic oscillatory behavior in high cell-density continuous cultures. Oscillatory behavior provides a unique opportunity for quantitating the robustness of metabolism, as cells respond to changes by inherently compromising metabolic efficiency. Here, we quantify the limits of metabolic robustness in self-oscillating autotrophic continuous cultures of the gas-fermenting acetogen Clostridium autoethanogenum Online gas analysis and high-resolution temporal metabolomics showed oscillations in gas uptake rates and extracellular byproducts synchronized with biomass levels. The data show initial growth on CO, followed by growth on CO and H2 Growth on CO and H2 results in an accelerated growth phase, after which a downcycle is observed in synchrony with a loss in H2 uptake. Intriguingly, oscillations are not linked to translational control, as no differences were observed in protein expression during oscillations. Intracellular metabolomics analysis revealed decreasing levels of redox ratios in synchrony with the cycles. We then developed a thermodynamic metabolic flux analysis model to investigate whether regulation in acetogens is controlled at the thermodynamic level. We used endo- and exo-metabolomics data to show that the thermodynamic driving force of critical reactions collapsed as H2 uptake is lost. The oscillations are coordinated with redox. The data indicate that metabolic oscillations in acetogen gas fermentation are controlled at the thermodynamic level.


Assuntos
Reatores Biológicos/microbiologia , Clostridium/metabolismo , Metabolismo Energético , Fermentação , Processos Autotróficos , Biomassa , Monóxido de Carbono/metabolismo , Hidrogênio/metabolismo , Metabolômica , Oxirredução , Proteômica , Termodinâmica
15.
Proc Natl Acad Sci U S A ; 117(23): 12624-12635, 2020 06 09.
Artigo em Inglês | MEDLINE | ID: mdl-32434915

RESUMO

In oxygenic photosynthesis, light-driven oxidation of water to molecular oxygen is carried out by the oxygen-evolving complex (OEC) in photosystem II (PS II). Recently, we reported the room-temperature structures of PS II in the four (semi)stable S-states, S1, S2, S3, and S0, showing that a water molecule is inserted during the S2 → S3 transition, as a new bridging O(H)-ligand between Mn1 and Ca. To understand the sequence of events leading to the formation of this last stable intermediate state before O2 formation, we recorded diffraction and Mn X-ray emission spectroscopy (XES) data at several time points during the S2 → S3 transition. At the electron acceptor site, changes due to the two-electron redox chemistry at the quinones, QA and QB, are observed. At the donor site, tyrosine YZ and His190 H-bonded to it move by 50 µs after the second flash, and Glu189 moves away from Ca. This is followed by Mn1 and Mn4 moving apart, and the insertion of OX(H) at the open coordination site of Mn1. This water, possibly a ligand of Ca, could be supplied via a "water wheel"-like arrangement of five waters next to the OEC that is connected by a large channel to the bulk solvent. XES spectra show that Mn oxidation (τ of ∼350 µs) during the S2 → S3 transition mirrors the appearance of OX electron density. This indicates that the oxidation state change and the insertion of water as a bridging atom between Mn1 and Ca are highly correlated.


Assuntos
Fotossíntese , Complexo de Proteína do Fotossistema II/metabolismo , Hidrogênio/metabolismo , Magnésio/metabolismo , Oxirredução , Oxigênio/metabolismo , Fótons , Complexo de Proteína do Fotossistema II/química , Quinonas/metabolismo , Água/metabolismo
16.
J Biosci Bioeng ; 130(2): 149-158, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32414665

RESUMO

The hyperthermophilic archaeon Thermococcus kodakarensis can grow on pyruvate or maltooligosaccharides through H2 fermentation. H2 production levels of members of the Thermococcales are high, and studies to improve their production potential have been reported. Although H2 production is primary metabolism, here we aimed to partially uncouple cell growth and H2 production of T. kodakarensis. Additional A1-type ATPase genes were introduced into T. kodakarensis KU216 under the control of two promoters; the strong constitutive cell surface glycoprotein promoter, Pcsg, and the sugar-inducible fructose-1,6-bisphosphate aldolase promoter, Pfba. Whereas cells with the A1-type ATPase genes under the control of Pcsg displayed only trace levels of growth, cells with Pfba (strain KUA-PF) displayed growth sufficient for further analysis. Increased levels of A1-type ATPase protein were detected in KUA-PF cells grown on pyruvate or maltodextrin, when compared to the levels in the host strain KU216. The growth and H2 production levels of strain KUA-PF with pyruvate or maltodextrin as a carbon and electron source were analyzed and compared to those of the host strain KU216. Compared to a small decrease in total H2 production, significantly larger decreases in cell growth were observed, resulting in an increase in cell-specific H2 production. Quantification of the substrate also revealed that ATPase overexpression led to increased cell-specific pyruvate and maltodextrin consumptions. The results clearly indicate that ATPase production results in partial uncoupling of cell growth and H2 production in T. kodakarensis.


Assuntos
Adenosina Trifosfatases/genética , Adenosina Trifosfatases/metabolismo , Regulação da Expressão Gênica em Archaea , Hidrogênio/metabolismo , Thermococcus/enzimologia , Thermococcus/genética , Carbono/metabolismo , Dosagem de Genes/fisiologia , Regulação da Expressão Gênica em Archaea/genética , Organismos Geneticamente Modificados/metabolismo , Polissacarídeos/metabolismo , Ácido Pirúvico/metabolismo
17.
Nat Microbiol ; 5(5): 655-667, 2020 05.
Artigo em Inglês | MEDLINE | ID: mdl-32341569

RESUMO

The discovery of Asgard archaea, phylogenetically closer to eukaryotes than other archaea, together with improved knowledge of microbial ecology, impose new constraints on emerging models for the origin of the eukaryotic cell (eukaryogenesis). Long-held views are metamorphosing in favour of symbiogenetic models based on metabolic interactions between archaea and bacteria. These include the classical Searcy's and Hydrogen hypothesis, and the more recent Reverse Flow and Entangle-Engulf-Endogenize models. Two decades ago, we put forward the Syntrophy hypothesis for the origin of eukaryotes based on a tripartite metabolic symbiosis involving a methanogenic archaeon (future nucleus), a fermentative myxobacterial-like deltaproteobacterium (future eukaryotic cytoplasm) and a metabolically versatile methanotrophic alphaproteobacterium (future mitochondrion). A refined version later proposed the evolution of the endomembrane and nuclear membrane system by invagination of the deltaproteobacterial membrane. Here, we adapt the Syntrophy hypothesis to contemporary knowledge, shifting from the original hydrogen and methane-transfer-based symbiosis (HM Syntrophy) to a tripartite hydrogen and sulfur-transfer-based model (HS Syntrophy). We propose a sensible ecological scenario for eukaryogenesis in which eukaryotes originated in early Proterozoic microbial mats from the endosymbiosis of a hydrogen-producing Asgard archaeon within a complex sulfate-reducing deltaproteobacterium. Mitochondria evolved from versatile, facultatively aerobic, sulfide-oxidizing and, potentially, anoxygenic photosynthesizing alphaproteobacterial endosymbionts that recycled sulfur in the consortium. The HS Syntrophy hypothesis accounts for (endo)membrane, nucleus and metabolic evolution in a realistic ecological context. We compare and contrast the HS Syntrophy hypothesis to other models of eukaryogenesis, notably in terms of the mode and tempo of eukaryotic trait evolution, and discuss several model predictions and how these can be tested.


Assuntos
Archaea/metabolismo , Evolução Biológica , Eucariotos/metabolismo , Células Eucarióticas/metabolismo , Filogenia , Archaea/genética , Bactérias/genética , Núcleo Celular , Eucariotos/genética , Genoma Arqueal , Hidrogênio/metabolismo , Membranas/metabolismo , Mitocôndrias/metabolismo , Oxirredução , Enxofre/metabolismo , Simbiose/fisiologia
18.
Biochim Biophys Acta Bioenerg ; 1861(8): 148208, 2020 08 01.
Artigo em Inglês | MEDLINE | ID: mdl-32339488

RESUMO

Photosynthetic microorganisms such as the cyanobacterium Synechocystis sp. PCC 6803 (Synechocystis) can be exploited for the light-driven synthesis of valuable compounds. Thermodynamically, it is most beneficial to branch-off photosynthetic electrons at ferredoxin (Fd), which provides electrons for a variety of fundamental metabolic pathways in the cell, with the ferredoxin-NADP+ Oxido-Reductase (FNR, PetH) being the main target. In order to re-direct electrons from Fd to another consumer, the high electron transport rate between Fd and FNR has to be reduced. Based on our previous in vitro experiments, corresponding FNR-mutants at position FNR_K190 (Wiegand, K., et al.: "Rational redesign of the ferredoxin-NADP-oxido-reductase/ferredoxin-interaction for photosynthesis-dependent H2-production". Biochim Biophys Acta, 2018) have been generated in Synechocystis cells to study their impact on the cellular metabolism and their potential for a future hydrogen-producing design cell. Out of two promising candidates, mutation FNR_K190D proved to be lethal due to oxidative stress, while FNR_K190A was successfully generated and characterized: The light induced NADPH formation is clearly impaired in this mutant and it shows also major metabolic adaptations like a higher glucose metabolism as evidenced by quantitative mass spectrometric analysis. These results indicate a high potential for the future use of photosynthetic electrons in engineered design cells - for instance for hydrogen production. They also show substantial differences of interacting proteins in an in vitro environment vs. physiological conditions in whole cells.


Assuntos
Hidrogênio/metabolismo , Fotossíntese , Synechocystis/metabolismo , Água/metabolismo , Sequência de Bases , Transporte de Elétrons , Modelos Moleculares , Mutação , Oxirredutases/genética , Oxirredutases/metabolismo , Conformação Proteica
19.
Sci Rep ; 10(1): 5859, 2020 04 03.
Artigo em Inglês | MEDLINE | ID: mdl-32246095

RESUMO

We have developed Si-based agent which can generate a large amount of hydrogen. Si-based agent continues generating hydrogen for more than 24 h by the reaction with water under conditions similar to those in bowels, i.e., pH8.3 and 36 °C, and generates ~400 mL hydrogen. To investigate beneficial effects for diseases associated with oxidative stress, Si-based agent is administered to remnant kidney rats and Parkinson's disease mice. Rats are fed with control or Si-based agent-containing diet for 8 weeks. Si-based agent is found to greatly suppress the development of renal failure and the parameters of oxidative stress. Treatment with Si-based agent in a mouse model of hemi-Parkinson's disease induced by 6-hydroxydopamine attenuated degeneration of dopaminergic neurons and prevented impairment of motor balance and coordination. These findings indicate that the Si-based agent shows renoprotective and neuroprotective effects presumably via suppression of oxidative stress by generation of hydrogen.


Assuntos
Hidrogênio/metabolismo , Fármacos Neuroprotetores/uso terapêutico , Doença de Parkinson/tratamento farmacológico , Insuficiência Renal Crônica/tratamento farmacológico , Silício/uso terapêutico , Animais , Modelos Animais de Doenças , Rim/efeitos dos fármacos , Rim/metabolismo , Rim/patologia , Masculino , Camundongos , Estresse Oxidativo , Ratos , Ratos Sprague-Dawley , Reação em Cadeia da Polimerase em Tempo Real , Insuficiência Renal Crônica/patologia , Teste de Desempenho do Rota-Rod , Tirosina 3-Mono-Oxigenase/metabolismo
20.
Sci Total Environ ; 722: 137795, 2020 Jun 20.
Artigo em Inglês | MEDLINE | ID: mdl-32208247

RESUMO

Considering the future energy demand and pollution to the environment, biohydrogen, a biofuel, produced from biological sources have garnered increased attention. The present review emphasis the various techniques and methods employed to enumerate the microbial community and enhancement of hydrogen production by dark fermentation. Notably, molecular techniques such as terminal restriction fragment length polymorphism (T-RFLP), quantitative real-time PCR (q-PCR), fluorescent in-situ hybridization (FISH), denaturing gradient gel electrophoresis (DGGE), ribosomal intergenic spacer analysis (RISA), and next generation sequencing (NGS) have been extensively discussed on identifying the microbial population in hydrogen production. Further, challenges and merits of the molecular techniques have been elaborated.


Assuntos
Hidrogênio/metabolismo , Eletroforese em Gel de Gradiente Desnaturante , Sequenciamento de Nucleotídeos em Larga Escala , Microbiota , Reação em Cadeia da Polimerase , Polimorfismo de Fragmento de Restrição
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