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1.
Inorg Chem ; 59(2): 968-971, 2020 Jan 21.
Artigo em Inglês | MEDLINE | ID: mdl-31891256

RESUMO

A dithiolate/hydride bridged Fe-Ni complex, [(CN)(CO)2FeII(µ-pdt)(µ-H)NiII(CN)(PCy3)]- (2, pdt = propane-1,3-dithiolate) has been synthesized by the reaction of [(CN)2(CO)2FeII(pdt)]2- with [NiII(Cl)(H)(PCy3)2] as a synthetic analogue of the Ni-R state of the active site of the [Ni-Fe] hydrogenase. X-ray crystallography of this model complex suggests that the hydride unsymmetrically binds to Ni and Fe similar to natural [Ni-Fe] hydrogenases.


Assuntos
Monóxido de Carbono/química , Complexos de Coordenação/química , Cianetos/química , Hidrogenase/química , Tolueno/análogos & derivados , Monóxido de Carbono/metabolismo , Domínio Catalítico , Complexos de Coordenação/metabolismo , Cianetos/metabolismo , Hidrogenase/metabolismo , Ferro/química , Ferro/metabolismo , Modelos Moleculares , Conformação Molecular , Níquel/química , Níquel/metabolismo , Tolueno/química , Tolueno/metabolismo
2.
Biochim Biophys Acta Bioenerg ; 1861(1): 148087, 2020 01 01.
Artigo em Inglês | MEDLINE | ID: mdl-31669490

RESUMO

Electron bifurcating, [FeFe]-hydrogenases are recently described members of the hydrogenase family and catalyze a combination of exergonic and endergonic electron exchanges between three carriers (2 ferredoxinred- + NAD(P)H + 3 H+ = 2 ferredoxinox + NAD(P)+ + 2 H2). A thermodynamic analysis of the bifurcating, [FeFe]-hydrogenase reaction, using electron path-independent variables, quantified potential biological roles of the reaction without requiring enzyme details. The bifurcating [FeFe]-hydrogenase reaction, like all bifurcating reactions, can be written as a sum of two non-bifurcating reactions. Therefore, the thermodynamic properties of the bifurcating reaction can never exceed the properties of the individual, non-bifurcating, reactions. The bifurcating [FeFe]-hydrogenase reaction has three competitive properties: 1) enabling NAD(P)H-driven proton reduction at pH2 higher than the concurrent operation of the two, non-bifurcating reactions, 2) oxidation of NAD(P)H and ferredoxin simultaneously in a 1:1 ratio, both are produced during typical glucose fermentations, and 3) enhanced energy conservation (~10 kJ mol-1 H2) relative to concurrent operation of the two, non-bifurcating reactions. Our analysis demonstrated ferredoxin E°' largely determines the sensitivity of the bifurcating reaction to pH2, modulation of the reduced/oxidized electron carrier ratios contributed less to equilibria shifts. Hydrogenase thermodynamics data were integrated with typical and non-typical glycolysis pathways to evaluate achieving the 'Thauer limit' (4 H2 per glucose) as a function of temperature and pH2. For instance, the bifurcating [FeFe]-hydrogenase reaction permits the Thauer limit at 60 °C if pH 2 ≤ ~10 mbar. The results also predict Archaea, expressing a non-typical glycolysis pathway, would not benefit from a bifurcating [FeFe]-hydrogenase reaction; interestingly, no Archaea have been observed experimentally with a [FeFe]-hydrogenase enzyme.


Assuntos
Proteínas de Bactérias , Hidrogênio , Hidrogenase , Proteínas com Ferro-Enxofre , Thermotoga maritima/enzimologia , Anaerobiose/fisiologia , Proteínas de Bactérias/química , Proteínas de Bactérias/metabolismo , Hidrogênio/química , Hidrogênio/metabolismo , Hidrogenase/química , Hidrogenase/metabolismo , Proteínas com Ferro-Enxofre/química , Proteínas com Ferro-Enxofre/metabolismo , Oxirredução , Termodinâmica
3.
J Photochem Photobiol B ; 199: 111597, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31450130

RESUMO

The green microalgae Parachlorella kessleri RA-002 isolated in Armenia can produce biohydrogen (H2) during oxygenic photosynthesis. Addition of protonophores, carbonyl cyanide m-chlorophenylhydrazone (CCCP) and 2,4-dinitrophenol (DNF) enhances H2 yield in P. kessleri. The maximal H2 yield of ~2.20 and 2.08 mmol L-1 was obtained in the presence of 15 µM CCCP and 50 µM DNF, respectively. During dark conditions H2 production by P. kessleri was not observed even in the presence of protonophores, indicating that H2 formation in these algae was mediated by light conditions. The enhancing effect of protonophores can be coupled with dissipation of proton motive force across thylakoid membrane in P. kessleri, facilitating the availability of protons and electrons to [Fe-Fe]-hydrogenase, which led to formation of H2. At the same time H2 production was not observed in the presence of diuron (3-(3,4-dichlorophenyl)-1,1-dimethylurea), a specific inhibitor of PS II. Moreover, diuron inhibits H2 yield in P. kessleri in the presence of protonophores. The inhibitory effect of diuron coupled with suppression of electron transfer from PS II. The results showed that in these algae operates PS II-dependent pathway of H2 generation. This study is important for understanding of the mechanisms of H2 production by green microalgae P. kessleri and developing of its biotechnology.


Assuntos
2,4-Dinitrofenol/metabolismo , Carbonil Cianeto m-Clorofenil Hidrazona/metabolismo , Clorófitas/metabolismo , Hidrogênio/química , Microalgas/metabolismo , Fotossíntese/efeitos dos fármacos , Diurona/metabolismo , Transporte de Elétrons , Hidrogenase/metabolismo , Proteínas com Ferro-Enxofre/metabolismo , Luz , Oxirredução , Oxigênio/química , Fármacos Fotossensibilizantes/metabolismo , Prótons , Transdução de Sinais
4.
World J Microbiol Biotechnol ; 35(8): 116, 2019 Jul 22.
Artigo em Inglês | MEDLINE | ID: mdl-31332538

RESUMO

Exploration of renewable energy sources is an imperative task in order to replace fossil fuels and to diminish atmospheric pollution. Hydrogen is considered one of the most promising fuels for the future and implores further investigation to find eco-friendly ways toward viable production. Expansive processes like electrolysis and fossil fuels are currently being used to produce hydrogen. Biological hydrogen production (BHP) displays recyclable and economical traits, and is thus imperative for hydrogen economy. Three basic modes of BHP were investigated, including bio photolysis, photo fermentation and dark fermentation. Photosynthetic microorganisms could readily serve as powerhouses to successively produce this type of energy. Cyanobacteria, blue green algae (bio photolysis) and some purple non-sulfur bacteria (Photo fermentation) utilize solar energy and produce hydrogen during their metabolic processes. Ionic species, including hydrogen (H+) and electrons (e-) are combined into hydrogen gas (H2), with the use of special enzymes called hydrogenases in the case of bio photolysis, and nitrogenases catalyze the formation of hydrogen in the case of photo fermentation. Nevertheless, oxygen sensitivity of these enzymes is a drawback for bio photolysis and photo fermentation, whereas, the amount of hydrogen per unit substrate produced appears insufficient for dark fermentation. This review focuses on innovative advances in the bioprocess research, genetic engineering and bioprocess technologies such as microbial fuel cell technology, in developing bio hydrogen production.


Assuntos
Eletrólise , Hidrogênio/metabolismo , Fontes de Energia Bioelétrica , Reatores Biológicos/microbiologia , Cianobactérias/metabolismo , Fermentação , Hidrogenase/metabolismo , Oxigênio/metabolismo , Fotólise , Fotossíntese
5.
Bioresour Technol ; 289: 121706, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31279320

RESUMO

Microbial electrosynthesis (MES) is a promising technology to convert CO2 and electricity into the biofuel methane using methanogens. Until now, most investigations on electro-methanogenesis are "proof-of-principle" studies. In this paper, different strains were quantitatively compared in regard to final methane concentration, yields based on CO2-conversion, productivities as well as Coulombic efficiencies in order to identify suitable organisms for MES. Methanococcus vannielii, Methanococcus maripaludis, Methanolacinia petrolearia, Methanobacterium congolense, and Methanoculleus submarinus were able to produce methane via MES at -700 mV vs. standard hydrogen electrode (SHE). Beside methane also biological H2 production was detected during MES, which might be due to the involvement of hydrogenases. A direct electron transfer pathway is most likely. Obviously, M. maripaludis is the most resource efficient methane producer in microbial electrosynthesis regarding the methane productivity (8.81 ±â€¯0.51 mmol m-2 d-1) and the Coulombic efficiency (58.9 ±â€¯0.8%).


Assuntos
Dióxido de Carbono/metabolismo , Metano/biossíntese , Mathanococcus/metabolismo , Methanomicrobiaceae/metabolismo , Eletrodos , Hidrogenase/metabolismo , Methanobacterium/metabolismo
6.
ScientificWorldJournal ; 2019: 1030236, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31346323

RESUMO

The unicellular halotolerant cyanobacterium Aphanothece halophytica is a potential dark fermentative producer of molecular hydrogen (H2) that produces very little H2 under illumination. One factor limiting the H2 photoproduction of this cyanobacterium is an inhibition of bidirectional hydrogenase activity by oxygen (O2) obtained from splitting water molecules via photosystem II activity. The present study aimed to investigate the effects of the photosystem II inhibitors carbonyl cyanide m-chlorophenyl hydrazone (CCCP) and 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) on H2 production of A. halophytica under light and dark conditions and on photosynthetic and respiratory activities. The results showed that A. halophytica treated with CCCP and DCMU produced H2 at three to five times the rate of untreated cells, when exposed to light. The highest H2 photoproduction rates, 2.26 ±â€Š0.24 and 3.63 ±â€Š0.26 µmol H2 g-1 dry weight h-1, were found in cells treated with 0.5 µM CCCP and 50 µM DCMU, respectively. Without inhibitor treatment, A. halophytica incubated in the dark showed a significant increase in H2 production compared with cells that were incubated in the light. Only CCCP treatment increased H2 production of A. halophytica during dark incubation, because CCCP functions as an uncoupling agent of oxidative phosphorylation. The highest dark fermentative H2 production rate of 39.50 ±â€Š2.13 µmol H2 g-1 dry weight h-1 was found in cells treated with 0.5 µM CCCP after 2 h of dark incubation. Under illumination, CCCP and DCMU inhibited chlorophyll fluorescence, resulting in a low level of O2, which promoted bidirectional hydrogenase activity in A. halophytica cells. In addition, only CCCP enhanced the respiration rate, further reducing the O2 level. In contrast, DCMU reduced the respiration rate in A. halophytica.


Assuntos
Carbonil Cianeto m-Clorofenil Hidrazona/farmacologia , Cianobactérias/efeitos dos fármacos , Cianobactérias/metabolismo , Diurona/farmacologia , Hidrogênio/metabolismo , Complexo de Proteína do Fotossistema II/antagonistas & inibidores , Respiração Celular/efeitos dos fármacos , Respiração Celular/efeitos da radiação , Clorofila A/metabolismo , Escuridão , Hidrogenase/metabolismo , Fotossíntese/efeitos dos fármacos
7.
Bioresour Technol ; 289: 121762, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31311731

RESUMO

In this work, glucose addition (0.7 g l-1) almost doubled hydrogen yield of Chlorella pyrenoidosa (121.1 ml l-1 vs 65.5 ml l-1), with a positive correlation between hydrogen production and glucose consumption (-0.977, P < 0.01). When the electrons transport from water photolysis to algal hydrogenase was inhibited, the hydrogen productivity declined by 21.1%; whereas it dramatically decreased by 70.9% when the algal nicotinamide adeninedinucleotide dehydrogenase (NADH) was inhibited. Therefore, in the presence of glucose, the electrons for algae based hydrogen production would be mainly from glucose glycolysis rather than water photolysis. Further deuterated-glucose trial indicated that the glucose might serve as an electron donor for algal hydrogenases. Finally, a tentative electron transport route from glucose to algal hydrogenase was proposed, hoping to provide more scientific direction for further algae-based hydrogen production improvement.


Assuntos
Chlorella/metabolismo , Hidrogênio/metabolismo , Hidrogenase/metabolismo , Transporte de Elétrons , Elétrons , Glucose/metabolismo , Fotólise
8.
Phys Chem Chem Phys ; 21(27): 14638-14645, 2019 Jul 10.
Artigo em Inglês | MEDLINE | ID: mdl-31215568

RESUMO

In [Fe-Fe] hydrogenase mimic systems the ene-1,2-dithiolene ligands play an important role in the stabilisation of the redox-active metal center. This is demonstrated by the benzenedithiolene (bdt) analogue, featuring six terminal carbonyl ligands connected to a di-iron metal center, i.e. [Fe2(bdt)(CO)6]. Here we present a combined experimental and theoretical study that elucidates key intermediates [Fe2(bdt)(CO)6]1- and [Fe2(bdt)(µ-CO)(CO)5]2- in the electrocatalytic production of dihydrogen. A DFT study shows that [Fe2(bdt)(CO)6]1- is the kinetic product after the first one electron reduction, while the previously proposed bridging intermediate species [Fe2(bdt)(µ-CO)(CO)5]1- is kinetically inaccessible. The doubly reduced species [Fe2(bdt)(µ-CO)(CO)5]2- was for the first time structurally characterized using EXAFS. XANES analysis confirms the existence of reduced iron zero species and confirms the distorted geometry that was suggested by the DFT calculations. Combining IR, UV-vis and XAS spectroscopic results with TD-DFT and FEFF calculations enabled us to assign the key-intermediate [Fe2(bdt)(CO)6]2-. This study emphasizes the strengths of combining computational chemistry with advanced spectroscopy techniques.


Assuntos
Hidrogenase/química , Proteínas com Ferro-Enxofre/química , Modelos Químicos , Análise Espectral , Mimetismo Biológico , Catálise , Compostos Ferrosos/química , Hidrogenase/metabolismo , Proteínas com Ferro-Enxofre/metabolismo
9.
ISME J ; 13(10): 2617-2632, 2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-31243332

RESUMO

Farmed ruminants are the largest source of anthropogenic methane emissions globally. The methanogenic archaea responsible for these emissions use molecular hydrogen (H2), produced during bacterial and eukaryotic carbohydrate fermentation, as their primary energy source. In this work, we used comparative genomic, metatranscriptomic and co-culture-based approaches to gain a system-wide understanding of the organisms and pathways responsible for ruminal H2 metabolism. Two-thirds of sequenced rumen bacterial and archaeal genomes encode enzymes that catalyse H2 production or consumption, including 26 distinct hydrogenase subgroups. Metatranscriptomic analysis confirmed that these hydrogenases are differentially expressed in sheep rumen. Electron-bifurcating [FeFe]-hydrogenases from carbohydrate-fermenting Clostridia (e.g., Ruminococcus) accounted for half of all hydrogenase transcripts. Various H2 uptake pathways were also expressed, including methanogenesis (Methanobrevibacter), fumarate and nitrite reduction (Selenomonas), and acetogenesis (Blautia). Whereas methanogenesis-related transcripts predominated in high methane yield sheep, alternative uptake pathways were significantly upregulated in low methane yield sheep. Complementing these findings, we observed significant differential expression and activity of the hydrogenases of the hydrogenogenic cellulose fermenter Ruminococcus albus and the hydrogenotrophic fumarate reducer Wolinella succinogenes in co-culture compared with pure culture. We conclude that H2 metabolism is a more complex and widespread trait among rumen microorganisms than previously recognised. There is evidence that alternative hydrogenotrophs, including acetogenic and respiratory bacteria, can prosper in the rumen and effectively compete with methanogens for H2. These findings may help to inform ongoing strategies to mitigate methane emissions by increasing flux through alternative H2 uptake pathways, including through animal selection, dietary supplementation and methanogenesis inhibitors.


Assuntos
Archaea/metabolismo , Bactérias/metabolismo , Hidrogênio/metabolismo , Metano/metabolismo , Rúmen/microbiologia , Ruminantes/microbiologia , Animais , Archaea/classificação , Archaea/genética , Archaea/isolamento & purificação , Bactérias/classificação , Bactérias/genética , Bactérias/isolamento & purificação , Sequência de Bases , Celulose/metabolismo , Euryarchaeota/genética , Fermentação , Hidrogenase/genética , Hidrogenase/metabolismo , Rúmen/metabolismo , Ruminantes/metabolismo
10.
Dalton Trans ; 48(23): 8034-8038, 2019 Jun 21.
Artigo em Inglês | MEDLINE | ID: mdl-31074752

RESUMO

A series of amidate-ligated pentadentate iron and cobalt complexes with N-heterocyclic pyridinol groups were proposed and computationally screened as potential catalysts for CO2 reduction. Density functional theory calculations reveal a ligand assisted heterolytic H2 cleavage mechanism with a total free energy barrier of 23.3 kcal mol-1 for the hydrogenation of CO2 to methanol catalysed by a pentadentate Co complex with a 2-[bis(pyridine-2-ylmethyl)]amino-N-3,9-purin-2-one ligand.


Assuntos
Materiais Biomiméticos/química , Dióxido de Carbono/química , Cobalto/química , Hidrogenase/metabolismo , Proteínas com Ferro-Enxofre/metabolismo , Ferro/química , Metanol/química , Compostos Organometálicos/química , Teoria da Densidade Funcional , Hidrogenação , Modelos Moleculares , Conformação Molecular , Termodinâmica
11.
Biotechnol J ; 14(10): e1900009, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31140716

RESUMO

During glucose-limited growth, a substantial input of adenosine triphosphate (ATP) is required for the production of ß-lactams by the filamentous fungus Penicillium chrysogenum. Formate dehydrogenase has been confirmed in P. chrysogenum for formate oxidation allowing an extra supply of ATP, and coassimilation of glucose and formate has the potential to increase penicillin production and biomass yield. In this study, the steady-state metabolite levels and fluxes in response to cofeeding of formate as an auxiliary substrate in glucose-limited chemostat cultures at the dilution rates (D) of both 0.03 h-1 and 0.05 h-1 are determined to evaluate the quantitative impact on the physiology of a high-yielding P. chrysogenum strain. It is observed that an equimolar addition of formate is conducive to an increase in both biomass yield and penicillin production at D = 0.03 h-1 , while this is not the case at D = 0.05 h-1 . In addition, a higher cytosolic redox status (NADH/NAD+ ), a higher intracellular glucose level, and lower penicillin productivity are only observed upon formate addition at D = 0.05 h-1 , which are virtually absent at D = 0.03 h-1 . In conclusion, the results demonstrate that the effect of formate as an auxiliary substrate on penicillin productivity in the glucose-limited chemostat cultivations of P. chrysogenum is not only dependent on the formate/glucose ratio as published before but also on the specific growth rate. The results also imply that the overall process productivity and quality regarding the use of formate should be further explored in an actual industrial-scale scenario.


Assuntos
Reatores Biológicos/microbiologia , Metabolômica/métodos , Penicillium chrysogenum/crescimento & desenvolvimento , Formiato Desidrogenases/metabolismo , Formiatos/metabolismo , Proteínas Fúngicas/metabolismo , Glucose/metabolismo , Hidrogenase/metabolismo , Complexos Multienzimáticos/metabolismo , Penicilinas/metabolismo , Penicillium chrysogenum/química , Estresse Fisiológico
12.
Adv Microb Physiol ; 74: 143-189, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31126530

RESUMO

Hydrogen metabolism plays a central role in sulfate-reducing bacteria of the Desulfovibrio genus and is based on hydrogenases that catalyze the reversible conversion of protons into dihydrogen. These metabolically versatile microorganisms possess a complex hydrogenase system composed of several enzymes of both [FeFe]- and [NiFe]-type that can vary considerably from one Desulfovibrio species to another. This review covers the molecular and physiological aspects of hydrogenases and H2 metabolism in Desulfovibrio but focuses particularly on our model bacterium Desulfovibrio fructosovorans. The search of hydrogenase genes in more than 30 sequenced genomes provides an overview of the distribution of these enzymes in Desulfovibrio. Our discussion will consider the significance of the involvement of electron-bifurcation in H2 metabolism.


Assuntos
Proteínas de Bactérias/fisiologia , Desulfovibrio/metabolismo , Hidrogênio/metabolismo , Hidrogenase/fisiologia , Proteínas de Bactérias/química , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Biocatálise , Desulfovibrio/enzimologia , Desulfovibrio/genética , Elétrons , Regulação Bacteriana da Expressão Gênica , Variação Genética , Hidrogenase/química , Hidrogenase/genética , Hidrogenase/metabolismo , Modelos Biológicos
13.
Adv Microb Physiol ; 74: 465-486, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31126535

RESUMO

Hydrogenase enzymes are currently under the international research spotlight due to emphasis on biologically produced hydrogen as one potential energy carrier to relinquish the requirement for 'fossil fuel' derived energy. Three major classes of hydrogenase exist in microbes all able to catalyze the reversible oxidation of dihydrogen to protons and electrons. These classes are defined by their active site metal content: [NiFe]-; [FeFe]- and [Fe]-hydrogenases. Of these the [NiFe]-hydrogenases have links to ancient forms of metabolism, utilizing hydrogen as the original source of reductant on Earth. This review progresses to highlight the Group 4 [NiFe]-hydrogenase enzymes that preferentially generate hydrogen exploiting various partner enzymes or ferredoxin, while in some cases translocating ions across biological membranes. Specific focus is paid to Group 4A, the Formate hydrogenlyase complexes. These are the combination of a six or nine subunit [NiFe]-hydrogenase with a soluble formate dehydrogenase to derived electrons from formate oxidation for proton reduction. The incidence, physiology, structure and biotechnological application of these complexes will be explored with attention on Escherichia coli Formate Hydrogenlyase-1 (FHL-1).


Assuntos
Formiato Desidrogenases/química , Formiato Desidrogenases/metabolismo , Hidrogênio/metabolismo , Hidrogenase/química , Hidrogenase/metabolismo , Complexos Multienzimáticos/química , Complexos Multienzimáticos/metabolismo , Biocatálise , Biotecnologia , Proteínas de Escherichia coli/química , Proteínas de Escherichia coli/genética , Proteínas de Escherichia coli/metabolismo , Formiato Desidrogenases/genética , Hidrogenase/genética , Modelos Moleculares , Complexos Multienzimáticos/genética , Óperon , Oxirredução
14.
Adv Microb Physiol ; 74: 487-514, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31126536

RESUMO

Hydrogenases are metal-containing biocatalysts that reversibly convert protons and electrons to hydrogen gas. This reaction can contribute in different ways to the generation of the proton motive force (PMF) of a cell. One means of PMF generation involves reduction of protons on the inside of the cytoplasmic membrane, releasing H2 gas, which being without charge is freely diffusible across the cytoplasmic membrane, where it can be re-oxidized to release protons. A second route of PMF generation couples transfer of electrons derived from H2 oxidation to quinone reduction and concomitant proton uptake at the membrane-bound heme cofactor. This redox-loop mechanism, as originally formulated by Mitchell, requires a second, catalytically distinct, enzyme complex to re-oxidize quinol and release the protons outside the cell. A third way of generating PMF is also by electron transfer to quinones but on the outside of the membrane while directly drawing protons through the entire membrane. The cofactor-less membrane subunits involved are proposed to operate by a conformational mechanism (redox-linked proton pump). Finally, PMF can be generated through an electron bifurcation mechanism, whereby an exergonic reaction is tightly coupled with an endergonic reaction. In all cases the protons can be channelled back inside through a F1F0-ATPase to convert the 'energy' stored in the PMF into the universal cellular energy currency, ATP. New and exciting discoveries employing these mechanisms have recently been made on the bioenergetics of hydrogenases, which will be discussed here and placed in the context of their contribution to energy conservation.


Assuntos
Archaea/metabolismo , Bactérias/metabolismo , Metabolismo Energético , Hidrogênio/metabolismo , Archaea/enzimologia , Bactérias/enzimologia , Membrana Celular/enzimologia , Membrana Celular/metabolismo , Transporte de Elétrons , Hidrogenase/metabolismo , Modelos Biológicos , Oxirredução , Bombas de Próton/metabolismo , Força Próton-Motriz , Quinonas/metabolismo
15.
BMC Genomics ; 20(1): 339, 2019 May 06.
Artigo em Inglês | MEDLINE | ID: mdl-31060509

RESUMO

BACKGROUND: Obligate sulfur oxidizing chemolithoauthotrophic strains of Hydrogenovibrio crunogenus have been isolated from multiple hydrothermal vent associated habitats. However, a hydrogenase gene cluster (encoding the hydrogen converting enzyme and its maturation/assembly machinery) detected on the first sequenced H. crunogenus strain (XCL-2) suggested that hydrogen conversion may also play a role in this organism. Yet, numerous experiments have underlined XCL-2's inability to consume hydrogen under the tested conditions. A recent study showed that the closely related strain SP-41 contains a homolog of the XCL-2 hydrogenase (a group 1b [NiFe]-hydrogenase), but that it can indeed use hydrogen. Hence, the question remained unresolved, why SP-41 is capable of using hydrogen, while XCL-2 is not. RESULTS: Here, we present the genome sequence of the SP-41 strain and compare it to that of the XCL-2 strain. We show that the chromosome of SP-41 codes for a further hydrogenase gene cluster, including two additional hydrogenases: the first appears to be a group 1d periplasmic membrane-anchored hydrogenase, and the second a group 2b sensory hydrogenase. The region where these genes are located was likely acquired horizontally and exhibits similarity to other Hydrogenovibrio species (H. thermophilus MA2-6 and H. marinus MH-110 T) and other hydrogen oxidizing Proteobacteria (Cupriavidus necator H16 and Ghiorsea bivora TAG-1 T). The genomes of XCL-2 and SP-41 show a strong conservation in gene order. However, several short genomic regions are not contained in the genome of the other strain. These exclusive regions are often associated with signs of DNA mobility, such as genes coding for transposases. They code for transport systems and/or extend the metabolic potential of the strains. CONCLUSIONS: Our results suggest that horizontal gene transfer plays an important role in shaping the genomes of these strains, as a likely mechanism for habitat adaptation, including, but not limited to the transfer of the hydrogen conversion ability.


Assuntos
Aclimatação , Ecossistema , Hidrogênio/metabolismo , Piscirickettsiaceae/genética , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Genoma Bacteriano , Hidrogenase/genética , Hidrogenase/metabolismo , Anotação de Sequência Molecular , Piscirickettsiaceae/classificação
16.
Arch Microbiol ; 201(7): 969-982, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31030239

RESUMO

In hydrothermal environments, carbon monoxide (CO) utilisation by thermophilic hydrogenogenic carboxydotrophs may play an important role in microbial ecology by reducing toxic levels of CO and providing H2 for fuelling microbial communities. We evaluated thermophilic hydrogenogenic carboxydotrophs by microbial community analysis. First, we analysed the correlation between carbon monoxide dehydrogenase (CODH)-energy-converting hydrogenase (ECH) gene cluster and taxonomic affiliation by surveying an increasing genomic database. We identified 71 genome-encoded CODH-ECH gene clusters, including 46 whose owners were not reported as hydrogenogenic carboxydotrophs. We identified 13 phylotypes showing > 98.7% identity with these taxa as potential hydrogenogenic carboxydotrophs in hot springs. Of these, Firmicutes phylotypes such as Parageobacillus, Carboxydocella, Caldanaerobacter, and Carboxydothermus were found in different environmental conditions and distinct microbial communities. The relative abundance of the potential thermophilic hydrogenogenic carboxydotrophs was low. Most of them did not show any symbiotic networks with other microbes, implying that their metabolic activities might be low.


Assuntos
Biodiversidade , Sedimentos Geológicos/microbiologia , Fontes Termais/microbiologia , Hidrogenase/genética , Microbiota/fisiologia , Aldeído Oxirredutases/metabolismo , Monóxido de Carbono/metabolismo , Firmicutes/fisiologia , Hidrogenase/metabolismo , Japão , Microbiota/genética , Complexos Multienzimáticos/metabolismo , Família Multigênica/genética
17.
Chem Commun (Camb) ; 55(39): 5579-5582, 2019 May 09.
Artigo em Inglês | MEDLINE | ID: mdl-30997456

RESUMO

A series of viologen related redox mediators of varying reduction potential has been characterized and their utility as electron shuttles between CdSe quantum dots and hydrogenase enzyme has been demonstrated. Tuning the mediator LUMO energy optimizes the performance of this hybrid photocatalytic system by balancing electron transfer rates of the shuttle.


Assuntos
Proteínas de Bactérias/metabolismo , Hidrogênio/metabolismo , Hidrogenase/metabolismo , Pontos Quânticos/química , Compostos de Cádmio/química , Catálise , Transporte de Elétrons , Hidrogênio/química , Luz , Pyrococcus furiosus/enzimologia , Teoria Quântica , Compostos de Selênio/química , Viologênios/química
18.
Bioresour Technol ; 284: 168-177, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-30933825

RESUMO

This study reports engineering of a hypertransformable variant of C. pasteurianum for bioconversion of glycerol into hydrogen (H2). A functional glycerol-triggered hydrogen pathway was engineered based on two approaches: (1) increasing product yield by overexpression of immediate enzyme catalyzing H2 production, (2) increasing substrate uptake by overexpression of enzymes involved in glycerol utilization. The first strategy aimed at overexpression of hydA gene encoding hydrogenase, and the second one, through combination of overexpression of dhaD1 and dhaK genes encoding glycerol dehydrogenase and dihydroxyacetone kinase. These genetic manipulations resulted in two recombinant strains (hydA++/dhaD1K++) capable of producing 97% H2 (v/v), with yields of 1.1 mol H2/mol glycerol in hydA overexpressed strain, and 0.93 mol H2/mol glycerol in dhaD1K overexpressed strain, which was 1.5 fold higher than wild type. Among two strains, dhaD1K++ consumed more glycerol than hydA++ which proves that overexpression of glycerol enzymes has enhanced glycerol intake rate.


Assuntos
Clostridium/enzimologia , Glicerol/metabolismo , Hidrogênio/metabolismo , Hidrogenase/metabolismo , Desidrogenase do Álcool de Açúcar/metabolismo , Hidrogenase/genética , Desidrogenase do Álcool de Açúcar/genética
19.
PLoS One ; 14(4): e0215029, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30973887

RESUMO

Electromethanogenesis is the bioreduction of carbon dioxide (CO2) to methane (CH4) utilizing an electrode as electron donor. Some studies have reported the active participation of Methanobacterium sp. in electron capturing, although no conclusive results are available. In this study, we aimed at determining short-time changes in the expression levels of [NiFe]-hydrogenases (Eha, Ehb and Mvh), heterodisulfide reductase (Hdr), coenzyme F420-reducing [NiFe]-hydrogenase (Frh), and hydrogenase maturation protein (HypD), according to the electron flow in independently connected carbon cloth cathodes poised at- 800 mV vs. standard hydrogen electrode (SHE). Amplicon massive sequencing of cathode biofilm confirmed the presence of an enriched Methanobacterium sp. population (>70% of sequence reads), which remained in an active state (78% of cDNA reads), tagging this archaeon as the main methane producer in the system. Quantitative RT-PCR determinations of ehaB, ehbL, mvhA, hdrA, frhA, and hypD genes resulted in only slight (up to 1.5 fold) changes for four out of six genes analyzed when cells were exposed to open (disconnected) or closed (connected) electric circuit events. The presented results suggested that suspected mechanisms for electron capturing were not regulated at the transcriptional level in Methanobacterium sp. for short time exposures of the cells to connected-disconnected circuits. Additional tests are needed in order to confirm proteins that participate in electron capturing in Methanobacterium sp.


Assuntos
Proteínas Arqueais/metabolismo , Fontes de Energia Bioelétrica , Eletrodos , Hidrogenase/metabolismo , Metano/metabolismo , Methanobacterium/enzimologia , Proteínas Arqueais/genética , Dióxido de Carbono , Hidrogenase/genética , Methanobacterium/genética , Methanobacterium/crescimento & desenvolvimento
20.
mBio ; 10(2)2019 03 12.
Artigo em Inglês | MEDLINE | ID: mdl-30862748

RESUMO

The Methanosarcinales, a lineage of cytochrome-containing methanogens, have recently been proposed to participate in direct extracellular electron transfer interactions within syntrophic communities. To shed light on this phenomenon, we applied electrochemical techniques to measure electron uptake from cathodes by Methanosarcina barkeri, which is an important model organism that is genetically tractable and utilizes a wide range of substrates for methanogenesis. Here, we confirm the ability of M. barkeri to perform electron uptake from cathodes and show that this cathodic current is linked to quantitative increases in methane production. The underlying mechanisms we identified include, but are not limited to, a recently proposed association between cathodes and methanogen-derived extracellular enzymes (e.g., hydrogenases) that can facilitate current generation through the formation of reduced and diffusible methanogenic substrates (e.g., hydrogen). However, after minimizing the contributions of such extracellular enzymes and using a mutant lacking hydrogenases, we observe a lower-potential hydrogen-independent pathway that facilitates cathodic activity coupled to methane production in M. barkeri Our electrochemical measurements of wild-type and mutant strains point to a novel and hydrogenase-free mode of electron uptake with a potential near -484 mV versus standard hydrogen electrode (SHE) (over 100 mV more reduced than the observed hydrogenase midpoint potential under these conditions). These results suggest that M. barkeri can perform multiple modes (hydrogenase-mediated and free extracellular enzyme-independent modes) of electrode interactions on cathodes, including a mechanism pointing to a direct interaction, which has significant applied and ecological implications.IMPORTANCE Methanogenic archaea are of fundamental applied and environmental relevance. This is largely due to their activities in a wide range of anaerobic environments, generating gaseous reduced carbon that can be utilized as a fuel source. While the bioenergetics of a wide variety of methanogens have been well studied with respect to soluble substrates, a mechanistic understanding of their interaction with solid-phase redox-active compounds is limited. This work provides insight into solid-phase redox interactions in Methanosarcina spp. using electrochemical methods. We highlight a previously undescribed mode of electron uptake from cathodes that is potentially informative of direct interspecies electron transfer interactions in the Methanosarcinales.


Assuntos
Fontes de Energia Bioelétrica , Eletrodos/microbiologia , Transporte de Elétrons , Metano/metabolismo , Methanosarcina barkeri/metabolismo , Deleção de Genes , Hidrogênio/metabolismo , Hidrogenase/genética , Hidrogenase/metabolismo
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