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1.
BMC Genomics ; 22(1): 475, 2021 Jun 25.
Artigo em Inglês | MEDLINE | ID: mdl-34171987

RESUMO

BACKGROUND: Halotolerant Fe (III) oxide reducers affiliated in the family Desulfuromonadaceae are ubiquitous and drive the carbon, nitrogen, sulfur and metal cycles in marine subsurface sediment. Due to their possible application in bioremediation and bioelectrochemical engineering, some of phylogenetically close Desulfuromonas spp. strains have been isolated through enrichment with crystalline Fe (III) oxide and anode. The strains isolated using electron acceptors with distinct redox potentials may have different abilities, for instance, of extracellular electron transport, surface recognition and colonization. The objective of this study was to identify the different genomic signatures between the crystalline Fe (III) oxide-stimulated strain AOP6 and the anode-stimulated strains WTL and DDH964 by comparative genome analysis. RESULTS: The AOP6 genome possessed the flagellar biosynthesis gene cluster, as well as diverse and abundant genes involved in chemotaxis sensory systems and c-type cytochromes capable of reduction of electron acceptors with low redox potentials. The WTL and DDH964 genomes lacked the flagellar biosynthesis cluster and exhibited a massive expansion of transposable gene elements that might mediate genome rearrangement, while they were deficient in some of the chemotaxis and cytochrome genes and included the genes for oxygen resistance. CONCLUSIONS: Our results revealed the genomic signatures distinctive for the ferric iron oxide- and anode-stimulated Desulfuromonas spp. strains. These findings highlighted the different metabolic abilities, such as extracellular electron transfer and environmental stress resistance, of these phylogenetically close bacterial strains, casting light on genome evolution of the subsurface Fe (III) oxide reducers.


Assuntos
Geobacter , Desulfuromonas , Eletrodos , Transporte de Elétrons , Compostos Férricos , Oxirredução
2.
Water Res ; 185: 116284, 2020 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-32818731

RESUMO

Surface chemistry is known to influence the formation, composition, and electroactivity of electron-conducting biofilms. However, understanding of the evolution of microbial composition during biofilm development and its impact on the electrochemical response is limited. Here we present voltammetric, microscopic and microbial community analysis of biofilms formed under fixed applied potential for modified graphite electrodes during early (90 h) and mature (340 h) growth phases. Electrodes modified to introduce hydrophilic groups (-NH2, -COOH and -OH) enhance early-stage biofilm formation compared to unmodified or electrodes modified with hydrophobic groups (-C2H5). In addition, early-stage films formed on hydrophilic electrodes are dominated by the gram-negative sulfur-reducing bacterium Desulfuromonas acetexigens while Geobacter sp. dominates on -C2H5 and unmodified electrodes. As biofilms mature, current generation becomes similar, and D. acetexigens dominates in all biofilms irrespective of surface chemistry. Electrochemistry of pure culture D. acetexigens biofilms reveal that this microbe is capable of forming electroactive biofilms producing considerable current density of > 9 A/m2 in a short period of potential-induced growth (~19 h following inoculation) using acetate as an electron donor. The inability of D. acetexigens biofilms to use H2 as a sole source electron donor for current generation shows promise for maximizing H2 recovery in single-chambered microbial electrolysis cell systems treating wastewaters.


Assuntos
Fontes de Energia Bioelétrica , Geobacter , Biofilmes , Desulfuromonas , Eletrodos
3.
J Am Chem Soc ; 140(40): 12798-12807, 2018 10 10.
Artigo em Inglês | MEDLINE | ID: mdl-30208703

RESUMO

Organisms that perform the de novo biosynthesis of cobalamin (vitamin B12) do so via unique pathways depending on the presence of oxygen in the environment. The anaerobic biosynthesis pathway of 5,6-dimethylbenzimidazole, the so-called "lower ligand" to the cobalt center, has been recently identified. This process begins with the conversion of 5-aminoimidazole ribotide (AIR) to 5-hydroxybenzimidazole (HBI) by the radical S-adenosyl-l-methionine (SAM) enzyme BzaF, also known as HBI synthase. In this work we report the characterization of a radical intermediate in the reaction of BzaF using electron paramagnetic resonance spectroscopy. Using various isotopologues of AIR, we extracted hyperfine parameters for a number of nuclei, allowing us to propose plausible chemical compositions and structures for this intermediate. Specifically, we find that an aminoimidazole radical is formed in close proximity to a fragment of the ribose ring. These findings induce the revision of past proposed mechanisms and illustrate the ability of radical SAM enzymes to tightly control the radical chemistry that they engender.


Assuntos
Proteínas de Bactérias/metabolismo , Benzimidazóis/metabolismo , Vias Biossintéticas , Desulfuromonas/metabolismo , Vitamina B 12/metabolismo , Anaerobiose , Espectroscopia de Ressonância de Spin Eletrônica , S-Adenosilmetionina/metabolismo
4.
FEMS Microbiol Lett ; 365(2)2018 02 01.
Artigo em Inglês | MEDLINE | ID: mdl-29228269

RESUMO

Electrochemical activity in bacteria has been observed in numerous environments and conditions. However, enrichments in circumneutral freshwater media where acetate is the main electron donor seem to invariably lead to the dominance of Geobacter spp. Here we report on an electroactive bacterial consortium which was enriched on acetate as electron donor, but in a medium which reproduces hydrolysed urine (high pH, high salinity and high free ammonia). The consortium was found to be free of Geobacter species, whereas a previously undescribed community dominated by species closely related to Pseudomonas and Desulfuromonas was established. The salient features of this community were as follows: (i) high electroactivity, with anodic current densities up to 47.4 ± 2.0 A m-2; (ii) haloalkaliphilicity, with top performance at a medium pH of 10 and 19.5 ± 0.5 mS cm-1; and (iii) a remarkably high tolerance to free ammonia toxicity at over 2200 mgNH3-N L-1. This community is likely to find applications in microbial electrochemical technology for nutrient recovery from source-separated urine.


Assuntos
Amônia/farmacologia , Desulfuromonas/efeitos dos fármacos , Farmacorresistência Bacteriana , Consórcios Microbianos/efeitos dos fármacos , Pseudomonas/efeitos dos fármacos , Fontes de Energia Bioelétrica , Eletrodos , Geobacter , RNA Ribossômico 16S/genética
5.
Environ Sci Pollut Res Int ; 24(32): 24803-24815, 2017 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-28913587

RESUMO

Reductive dechlorination performed by organohalide-respiring bacteria (OHRB) enables the complete detoxification of certain emerging groundwater pollutants such as perchloroethene (PCE). Environmental samples from a contaminated site incubated in a lab-scale microcosm (MC) study enable documentation of such reductive dechlorination processes. As compound-specific isotope analysis is used to monitor PCE degradation processes, nucleic acid analysis-like 16S-rDNA analysis-can be used to determine the key OHRB that are present. This study applied both methods to laboratory MCs prepared from environmental samples to investigate OHRB-specific isotope enrichment at PCE dechlorination. This method linkage can enhance the understanding of isotope enrichment patterns of distinct OHRB, which further contribute to more accurate evaluation, characterisation and prospection of natural attenuation processes. Results identified three known OHRB genera (Dehalogenimonas, Desulfuromonas, Geobacter) in diverse abundance within MCs. One species of Dehalogenimonas was potentially involved in complete reductive dechlorination of PCE to ethene. Furthermore, the isotopic effects of PCE degradation were clustered and two isotope enrichment factors (ε) (- 11.6‰, - 1.7‰) were obtained. Notably, ε values were independent of degradation rates and kinetics, but did reflect the genera of the dechlorinating OHRB.


Assuntos
Isótopos de Carbono/análise , Chloroflexi/metabolismo , Desulfuromonas/metabolismo , Geobacter/metabolismo , Tetracloroetileno/metabolismo , Biodegradação Ambiental , Água Subterrânea/química , Halogenação
6.
J Phys Chem B ; 119(25): 7968-74, 2015 Jun 25.
Artigo em Inglês | MEDLINE | ID: mdl-26039558

RESUMO

Metal-respiring bacteria are microorganisms capable of oxidizing organic pollutants present in wastewater and transferring the liberated electrons to an electrode. This ability has led to their application as catalysts in bioelectrochemical systems (BESs), a sustainable technology coupling bioremediation to electricity production. Crucial for the functioning of these BESs is a complex protein architecture consisting of several surface-exposed multiheme proteins, called outer membrane cytochromes, wiring the cell metabolism to the electrode. Although the role of these proteins has been increasingly understood, little is known about the protein-electrode interactions and their impact on the performance of BESs. In this study, we used surface-enhanced resonance Raman spectroscopy in combination with electrochemical techniques to unravel the nature of the protein-electrode interaction for the outer membrane cytochrome OmcB from Desulfuromonas acetoxidans (Dace). Comparing the spectroelectrochemical properties of OmcB bound directly to the electrode surface with those of the same protein embedded inside an electroactive biofilm, we have shown that the surface-exposed cytochromes of Dace biofilms are in direct contact with the electrode surface. Even if direct binding causes protein denaturation, the biofilm possesses the ability to minimize the extent of the damage maximizing the amount of cells in direct electrical communication with the electrode.


Assuntos
Proteínas da Membrana Bacteriana Externa/metabolismo , Fontes de Energia Bioelétrica , Biofilmes , Citocromos/metabolismo , Desulfuromonas/fisiologia , Eletrodos , Análise Espectral Raman
7.
Environ Sci Technol ; 49(7): 4193-9, 2015 Apr 07.
Artigo em Inglês | MEDLINE | ID: mdl-25734617

RESUMO

Natural pollution of groundwater by arsenic adversely affects the health of tens of millions of people worldwide, with the deltaic aquifers of SE Asia being particularly polluted. The pollution is caused primarily by, or as a side reaction of, the microbial reduction of sedimentary Fe(III)-oxyhydroxides, but the organism(s) responsible for As release have not been isolated. Here we report the first isolation of a dissimilatory arsenate reducer from sediments of the Bengal Basin in West Bengal. The bacterium, here designated WB3, respires soluble arsenate and couples its reduction to the oxidation of acetate; WB3 is therefore implicated in the process of arsenic pollution of groundwater, which is largely by arsenite. The bacterium WB3 is also capable of reducing dissolved Fe(III) citrate, solid Fe(III)-oxyhydroxide, and elemental sulfur, using acetate as the electron donor. It is a member of the Desulfuromonas genus and possesses a dissimilatory arsenate reductase that was identified using degenerate polymerase chain reaction primers. The sediment from which WB3 was isolated was brown, Pleistocene sand at a depth of 35.2 m below ground level (mbgl). This level was some 3 cm below the boundary between the brown sands and overlying reduced, gray, Holocene aquifer sands. The color boundary is interpreted to be a reduction front that releases As for resorption downflow, yielding a high load of labile As sorbed to the sediment at a depth of 35.8 mbgl and concentrations of As in groundwater that reach >1000 µg/L.


Assuntos
Arseniatos/química , Arsênio/análise , Desulfuromonas/isolamento & purificação , Monitoramento Ambiental/métodos , Água Subterrânea/microbiologia , Poluentes Químicos da Água/análise , Arsênio/química , Ásia Ocidental , Desulfuromonas/crescimento & desenvolvimento , Compostos Férricos/análise , Sedimentos Geológicos/química , Sedimentos Geológicos/microbiologia , Oxirredução , Poluentes Químicos da Água/química
8.
Int J Syst Evol Microbiol ; 65(Pt 5): 1686-1693, 2015 May.
Artigo em Inglês | MEDLINE | ID: mdl-25736408

RESUMO

A novel, mesophilic, obligately anaerobic, acetate-oxidizing, dissimilatory iron-, sulfur-, and manganese-reducing bacterium, designated strain ICBM(T), was obtained from an active, coalbed methane gas well in Indiana, USA. Strain ICBM(T) was a Gram-stain-negative, non-spore-forming, rod-shaped, non-motile bacterium that was rich in c-type cytochromes and formed red colonies in solid medium. Strain ICBM(T) conserved energy to support growth from the oxidation of acetate, propionate, pyruvate, malate, fumarate, succinate and dl-lactate, concomitant with dissimilatory iron reduction. Strain ICBM(T) fermented fumarate yielding succinate and acetate. Strain ICBM(T) was able to grow in the temperature range of 10 °C to 37 °C, NaCl concentration range of 0 to 1.2 M, and pH range of 6.5 to 8.0. The physiological characteristics of strain ICBM(T) indicated that it belongs to the Desulfuromonas cluster. The G+C content of its genomic DNA was 61.2 mol%. The predominant cellular fatty acids were C16 : 0 (39.3%), C16 : 1ω7c and/or iso-C15 : 0 2-OH (36.6%). The closest cultured phylogenetic relative of strain ICBM(T) was Desulfuromonas michiganensis BB1(T) with only 95% 16S rRNA gene sequence similarity. This confirmed that strain ICBM(T) is affiliated with the genus Desulfuromonas . On the basis of phenotypic and genotypic differences between strain ICBM(T) and other taxa of the genus Desulfuromonas , strain ICBM(T) represents a novel species for which the name Desulfuromonas carbonis sp. nov. is proposed (type strain ICBM(T) = DSM 29759(T) = JCM 30471(T)). Strain ICBM(T) is the first Fe(III)-, S(0)-, and Mn(IV)-reducing bacterium that was isolated from a coal bed.


Assuntos
Desulfuromonas/classificação , Campos de Petróleo e Gás/microbiologia , Filogenia , Técnicas de Tipagem Bacteriana , Composição de Bases , Citocromos/química , DNA Bacteriano/genética , Desulfuromonas/genética , Desulfuromonas/isolamento & purificação , Ácidos Graxos/química , Compostos Férricos/metabolismo , Indiana , Compostos de Manganês/metabolismo , Metano , Dados de Sequência Molecular , Oxirredução , RNA Ribossômico 16S/genética , Análise de Sequência de DNA
9.
Bioelectrochemistry ; 106(Pt A): 221-5, 2015 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-25717030

RESUMO

Two different saline sediments were used to inoculate potentiostatically controlled reactors (a type of microbial bioelectrochemical system, BES) operated in saline conditions (35 gNaCl l(-1)). Reactors were fed with acetate or a mixture of acetate and butyrate at two pH values: 7.0 or 5.5. Electroactive biofilm formation lag-phase, maximum current density production and coulombic efficiency were used to evaluate the overall performance of reactors. High current densities up to 8.5 A m(-2) were obtained using well-defined planar graphite electrodes. Additionally, biofilm microbial communities were characterized by CE-SSCP and 454 pyrosequencing. As a result of this procedure, two anode-respiring bacteria (ARB) always dominated the anodic biofilms: Geoalkalibacter subterraneus and/or Desulfuromonas acetoxidans. This suggests that a strong electrochemically driven selection process imposed by the applied potential occurs in the BES system. Moreover, the emergence of Glk. subterraneus in anodic biofilms significantly contributes to broaden the spectrum of high current producing microorganisms electrochemically isolated from environmental samples.


Assuntos
Fontes de Energia Bioelétrica/microbiologia , Biofilmes , Desulfuromonas/metabolismo , Condutividade Elétrica , Acetatos/metabolismo , Biofilmes/crescimento & desenvolvimento , Ácido Butírico/metabolismo , Desulfuromonas/fisiologia , Eletroquímica , Transporte de Elétrons , Concentração de Íons de Hidrogênio
10.
Ukr Biochem J ; 86(2): 16-25, 2014.
Artigo em Ucraniano | MEDLINE | ID: mdl-24868908

RESUMO

The mechanisms of electron transfer of association of chemoorganotrophic bacteria to the anode in microbial fuel cells are summarized in the survey. These mechanisms are not mutually exclusive and are divided into the mechanisms of mediator electron transfer, mechanisms of electron transfer with intermediate products of bacterial metabolism and mechanism of direct transfer of electrons from the cell surface. Thus, electron transfer mediators are artificial or synthesized by bacteria riboflavins and phenazine derivatives, which also determine the ability of bacteria to antagonism. The microorganisms with hydrolytic and exoelectrogenic activity are involved in electron transfer mechanisms that are mediated by intermediate metabolic products, which are low molecular carboxylic acids, alcohols, hydrogen etc. The direct transfer of electrons to insoluble anode is possible due to membrane structures (cytochromes, pili, etc.). Association of microorganisms, and thus the biochemical mechanisms of electron transfer depend on the origin of the inoculum, substrate composition, mass transfer, conditions of aeration, potentials and location of electrodes and others, that are defined by technological and design parameters.


Assuntos
Proteínas de Bactérias/química , Desulfovibrio/química , Desulfuromonas/química , Elétrons , Geobacter/química , Shewanella/química , Proteínas de Bactérias/metabolismo , Fontes de Energia Bioelétrica/estatística & dados numéricos , Desulfovibrio/metabolismo , Desulfuromonas/metabolismo , Eletrodos , Transporte de Elétrons , Geobacter/metabolismo , Oxirredução , Shewanella/metabolismo
11.
Artigo em Inglês | MEDLINE | ID: mdl-24279627

RESUMO

In order to develop a more effective and eco-friendly treatment technology, a full-scale tannery wastewater treatment plant with a sludge digestion system was augmented with a novel microbial consortium (BM-S-1). The aim of this study was to determine if the BM-S-1 could successfully treat the tannery wastewater in a full-scale treatment system without chemical pretreatment and to investigate effect of the augmentation on sludge production. Chemical oxygen demand (COD), total nitrogen (TN), total phosphorus (TP), chromium (Cr) and mixed liquor suspended solids (MLSS) were measured to monitor treated water quality and treatment efficiency. Microbial community structures in the treatment were also examined using pyrosequencing analysis of 16S rRNA gene and quantitative PCR (qPCR) of the nitrous oxide reductase gene (nosZ). The removal efficiencies of COD, TN, TP, and Cr were estimated to be 98.3%, 98.6%, 93.6%, and 88.5%, respectively, while the system without a continuous augmentation was broken down. The pyrosequencing analysis showed Brachymonas denitrificans to be the most dominant microbial population in the buffering tank (B; 37.5%). Potential polymeric substance degraders (Clostridia), sulfate reducers (Desulfuromonas palmitatis), and sulfur oxidizers (uncultured Thiobacillus) were dominant in the sludge digestion (SD) tank. The denitrifiers assayed by nosZ qPCR were dominant in B and SD. These microbial communities appeared to play important roles in removing nutrients and odor, and reducing sludge in the wastewater treatment plant without chemical pretreatment.


Assuntos
Consórcios Microbianos , Eliminação de Resíduos Líquidos/métodos , Águas Residuárias , Análise da Demanda Biológica de Oxigênio , Cromo/metabolismo , Clostridium/metabolismo , Desulfuromonas , Resíduos Industriais , Consórcios Microbianos/genética , Nitrogênio/metabolismo , Fósforo/metabolismo , Esgotos , Qualidade da Água
12.
Microbiology (Reading) ; 160(Pt 1): 123-129, 2014 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-24169815

RESUMO

Microbial oxidation of elemental sulfur with an electrode serving as the electron acceptor is of interest because this may play an important role in the recovery of electrons from sulfidic wastes and for current production in marine benthic microbial fuel cells. Enrichments initiated with a marine sediment inoculum, with elemental sulfur as the electron donor and a positively poised (+300 mV versus Ag/AgCl) anode as the electron acceptor, yielded an anode biofilm with a diversity of micro-organisms, including Thiobacillus, Sulfurimonas, Pseudomonas, Clostridium and Desulfuromonas species. Further enrichment of the anode biofilm inoculum in medium with elemental sulfur as the electron donor and Fe(III) oxide as the electron acceptor, followed by isolation in solidified sulfur/Fe(III) medium yielded a strain of Desulfuromonas, designated strain TZ1. Strain TZ1 effectively oxidized elemental sulfur to sulfate with an anode serving as the sole electron acceptor, at rates faster than Desulfobulbus propionicus, the only other organism in pure culture previously shown to oxidize S° with current production. The abundance of Desulfuromonas species enriched on the anodes of marine benthic fuel cells has previously been interpreted as acetate oxidation driving current production, but the results presented here suggest that sulfur-driven current production is a likely alternative.


Assuntos
Desulfuromonas/metabolismo , Eletricidade , Eletrodos/microbiologia , Sulfatos/metabolismo , Enxofre/metabolismo , Fontes de Energia Bioelétrica , DNA Bacteriano/química , DNA Bacteriano/genética , Desulfuromonas/classificação , Desulfuromonas/genética , Desulfuromonas/isolamento & purificação , Sedimentos Geológicos/microbiologia , Dados de Sequência Molecular , Oxirredução , Análise de Sequência de DNA
13.
Appl Microbiol Biotechnol ; 98(5): 2279-88, 2014 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-23963272

RESUMO

Monod kinetics are the foundation of mathematical models of many environmentally important biological processes, including the dehalorespiration of chlorinated ethene groundwater contaminants. The Monod parameters--qmax, the maximum specific substrate utilization rate, and KS, the half-saturation constant--are typically estimated in batch assays, which are superficially simple to prepare and maintain. However, if initial conditions in batch assays are not chosen carefully, it is unlikely that the estimated parameter values will be meaningful because they do not reflect microbial activity in the environmental system of interest, and/or they are not mathematically identifiable. The estimation of qmax and KS values that are highly correlated undoubtedly contributes significantly to the wide range in reported parameter values and may undermine efforts to use mathematical models to demonstrate the occurrence of natural attenuation or predict the performance of engineered bioremediation approaches. In this study, a series of experimental and theoretical batch kinetic assays were conducted using the tetrachloroethene-respirer Desulfuromonas michiganensis to systematically evaluate the effects of initial batch assay conditions, expressed as the initial substrate (S0)-to-initial biomass concentration (X0) ratio (S0/X0) and the S0/KS ratio on parameter correlation. An iterative approach to obtain meaningful Monod parameter estimates was developed and validated using three different strains and can be broadly applied to a range of other substrates and populations. While the S0/X0 ratio is critical to obtaining kinetic parameter estimates that reflect in situ microbial activity, this study shows that optimization of the S0/KS ratio is key to minimizing Monod parameter correlation.


Assuntos
Desulfuromonas/metabolismo , Tetracloroetileno/metabolismo , Modelos Teóricos
14.
Mikrobiol Z ; 75(2): 37-44, 2013.
Artigo em Ucraniano | MEDLINE | ID: mdl-23720962

RESUMO

Superoxide dismutase, as one of the enzymes of cells' antioxidant defensive system, catalyzes superoxide anion-radical (O2-) dismutation with O2 and H2O2 forming. The influence of such transition metal compounds, as FeSO4, FeCl3, MnCl2, NiCl2, and CoCl2 on superoxide dismutase activity of sulfur-reducing Desulfuromonas acetoxidans bacteria has been investigated. Maximal activity of the investigated enzyme has been observed accordingly under the influence of 1.0 mM of NiCl2, 2.0 mM of CoCl2 and MnCl2 on the second day and under the influence of 1.0 mM of FeCl3 and FeSO4 respectively, on the third day of growth in comparison with control samples. An increase of incubation time and concentration of metal compound in the medium caused the inhibition of superoxide dismutase activity.


Assuntos
Proteínas de Bactérias/antagonistas & inibidores , Desulfuromonas/efeitos dos fármacos , Desulfuromonas/enzimologia , Superóxido Dismutase/antagonistas & inibidores , Elementos de Transição/farmacologia , Proteínas de Bactérias/metabolismo , Cloretos/farmacologia , Cobalto/farmacologia , Meios de Cultura , Desulfuromonas/crescimento & desenvolvimento , Relação Dose-Resposta a Droga , Ensaios Enzimáticos , Compostos Férricos/farmacologia , Compostos Ferrosos/farmacologia , Cinética , Compostos de Manganês/farmacologia , Níquel/farmacologia , Oxirredução/efeitos dos fármacos , Superóxido Dismutase/metabolismo
15.
Biotechnol Lett ; 35(2): 273-8, 2013 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-23143172

RESUMO

A soil metagenomic library was constructed and screened for clones that conferred fosfomycin resistance. A novel protein with 46 % identity to UDP-N-acetylglucosamine enolpyruvyl transferase (MurA) from Desulfuromonas acetoxidans DSM 684 (GenBank accession number: ZP_01311756) was identified. Multiple sequence alignment revealed that the novel protein was a natural MurA, in which an aspartic acid instead of a cysteine was located in the active site. An Asp120Cys mutant of Escherichia coli was constructed from the subclone through site-specific mutagenesis, and minimum inhibitory concentration of fosfomycin for the resistant subclone and its mutant were determined. These results showed that fosfomycin resistance was a result of the aspartic acid in the active site. Analysis of all existing MurA sequences revealed that MurAs with an active site aspartic acid that can confer fosfomycin resistance occur in ~14 % of bacteria.


Assuntos
Alquil e Aril Transferases/metabolismo , Antibacterianos/farmacologia , Farmacorresistência Bacteriana , Escherichia coli/efeitos dos fármacos , Fosfomicina/farmacologia , Metagenoma , Microbiologia do Solo , Alquil e Aril Transferases/genética , Alquil e Aril Transferases/isolamento & purificação , Domínio Catalítico/genética , Desulfuromonas/genética , Escherichia coli/genética , Testes de Sensibilidade Microbiana , Mutagênese Sítio-Dirigida , Proteínas Mutantes/genética , Proteínas Mutantes/metabolismo , Homologia de Sequência de Aminoácidos
16.
J Biol Inorg Chem ; 17(1): 11-24, 2012 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-21805398

RESUMO

Cytochromes c(7) are periplasmic triheme proteins that have been reported exclusively in δ-proteobacteria. The structures of five triheme cytochromes identified in Geobacter sulfurreducens and one in Desulfuromonas acetoxidans have been determined. In addition to the hemes and axial histidines, a single aromatic residue is conserved in all these proteins-phenylalanine 15 (F15). PpcA is a member of the G. sulfurreducens cytochrome c(7) family that performs electron/proton energy transduction in addition to electron transfer that leads to the reduction of extracellular electron acceptors. For the first time we probed the role of the F15 residue in the PpcA functional mechanism, by replacing this residue with the aliphatic leucine by site-directed mutagenesis. The analysis of NMR spectra of both oxidized and reduced forms showed that the heme core and the overall fold of the mutated protein were not affected. However, the analysis of (1)H-(15)N heteronuclear single quantum coherence NMR spectra evidenced local rearrangements in the α-helix placed between hemes I and III that lead to structural readjustments in the orientation of heme axial ligands. The detailed thermodynamic characterization of F15L mutant revealed that the reduction potentials are more negative and the redox-Bohr effect is decreased. The redox potential of heme III is most affected. It is of interest that the mutation in F15, located between hemes I and III in PpcA, changes the characteristics of the two hemes differently. Altogether, these modifications disrupt the balance of the global network of cooperativities, preventing the F15L mutant protein from performing a concerted electron/proton transfer.


Assuntos
Grupo dos Citocromos c/química , Grupo dos Citocromos c/metabolismo , Fenilalanina/metabolismo , Sequência de Aminoácidos , Grupo dos Citocromos c/genética , Desulfuromonas/química , Geobacter/química , Mutagênese Sítio-Dirigida , Ressonância Magnética Nuclear Biomolecular , Oxirredução , Alinhamento de Sequência , Termodinâmica
17.
Dalton Trans ; 40(42): 11156-63, 2011 Nov 14.
Artigo em Inglês | MEDLINE | ID: mdl-21837318

RESUMO

The fate of actinyl species in the environment is closely linked to oxidation state, since the reduction of An(VI) to An(IV) greatly decreases their mobility due to the precipitation of the relatively insoluble An(IV) species. Here we study the mechanism of the reduction of [AnO(2)](2+) (An = U, Np, Pu) both in aqueous solution and by Fe(II) containing proteins and mineral surfaces, using density functional theory calculations. We find a disproportionation mechanism involving a An(V)-An(V) cation-cation complex, and we have investigated how these complexes are formed in the different environments. We find that the behaviour of U and Pu complexes are similar, but the reduction of Np(V) to Np(IV) would seems to be more difficult, in line with the experimental finding that Np(V) is generally more stable than U(V) or Pu(V). Although the models we have used are somewhat idealised, our calculations suggest that there are strong similarities between the biotic and abiotic reduction pathways.


Assuntos
Elementos da Série Actinoide/química , Citocromos/metabolismo , Ferro/química , Minerais/química , Teoria Quântica , Água/química , Catálise , Citocromos/química , Desulfuromonas/enzimologia , Compostos Ferrosos/química , Geobacter/enzimologia , Modelos Moleculares , Conformação Molecular , Netúnio/química , Oxirredução , Plutônio/química , Soluções , Propriedades de Superfície , Compostos de Urânio/química
18.
Metallomics ; 3(4): 349-53, 2011 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-21298162

RESUMO

Recent progress in bacterial genomic analysis has revealed a vast number of genes that encode c-type cytochromes that contain multiple heme cofactors. This high number of multiheme cytochromes in several bacteria has been correlated with their great respiratory flexibility, and in what concerns biotechnological applications, has been correlated with electricity production in Microbial Fuel Cells. Desulfuromonas acetoxidans, a member of the Geobactereaceae family, is one of these organisms for which the genome was recently made available, coding for 47 putative multiheme cytochromes. The growth of D. acetoxidans in different media allowed the identification of the cytochromes dominant in each condition. The triheme cytochrome c(7) is always present suggesting a key role in the bioenergetic metabolism of this organism, and a dodecaheme cytochrome of low homology with other proteins in the databases was also isolated. Different cytochromes are found for different growth conditions showing that their roles can be assigned to specific bioenergetic electron transfer routes.


Assuntos
Citocromos/metabolismo , Desulfuromonas/enzimologia , Fontes de Energia Bioelétrica , Citocromos/genética , Citocromos/isolamento & purificação , Desulfuromonas/genética , Desulfuromonas/crescimento & desenvolvimento , Genoma Bacteriano
19.
Biodegradation ; 22(4): 687-98, 2011 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-21053056

RESUMO

Tetrachloroethene (PCE) and trichloroethene (TCE) are common groundwater contaminants that also impact tidal flats, especially near urban and industrial areas. However, very little is known about dechlorinating microbial communities in tidal flats. Titanium pyrosequencing, 16S rRNA gene clone libraries, and dechlorinator-targeted quantitative real-time PCR (qPCR) characterized reductive dechlorinating activities and populations in tidal flat sediments collected from South Korea's central west coast near Kangwha. In microcosms established with surface sediments, PCE dechlorination to TCE began within 10 days and 100% of the initial amount of PCE was converted to TCE after 37 days. cis-1,2-Dichloroethene (cis-DCE) was observed as dechlorination end product in microcosms containing sediments collected from deeper zones (i.e., 35-40 cm below ground surface). Pyrosequencing of bacterial 16S rRNA genes and 16S rRNA gene-targeted qPCR results revealed Desulfuromonas michiganensis-like populations predominanted in both TCE and cis-DCE producing microcosms. Other abundant groups included Desulfuromonas thiophila and Pelobacter acidigallici-like populations in the surface sediment microcosms, and Desulfovibrio dechloracetivorans and Fusibacter paucivorans-like populations in the deeper sediment microcosms. Dehalococcoides spp. populations were not detected in these sediments before and after incubation with PCE. The results suggest that tidal flats harbor novel, salt-tolerant dechlorinating populations and that titanium pyrosequencing provides more detailed insight into community structure dynamics of the dechlorinating microcosms than conventional 16S rRNA gene sequencing or fingerprinting methods.


Assuntos
Cloro/metabolismo , Chloroflexi/genética , Desulfovibrio/genética , Desulfuromonas/genética , Poluição Ambiental/prevenção & controle , Sedimentos Geológicos/microbiologia , Consórcios Microbianos/genética , Tetracloroetileno/metabolismo , Biodegradação Ambiental , Chloroflexi/classificação , Chloroflexi/metabolismo , DNA Bacteriano/genética , Desulfovibrio/classificação , Desulfovibrio/metabolismo , Desulfuromonas/classificação , Desulfuromonas/metabolismo , Dicloroetilenos/metabolismo , Genes de RNAr , Sedimentos Geológicos/química , Filogenia , Reação em Cadeia da Polimerase , RNA Ribossômico 16S/genética , Análise de Sequência de DNA , Tricloroetileno/metabolismo
20.
Environ Sci Technol ; 45(3): 1093-9, 2011 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-21182287

RESUMO

In the vicinity of dense nonaqueous phase liquid (DNAPL) contaminant source zones, aqueous concentrations of tetrachloroethene (PCE) in groundwater may approach saturation levels. In this study, the ability of two PCE-respiring strains (Desulfuromonas michiganensis and Desulfitobacterium strain PCE1) to dechlorinate high concentrations of PCE was experimentally evaluated and depended on the initial biomass concentration. This suggests high PCE concentrations permanently inactivated a fraction of biomass, which, if sufficiently large, prevented dechlorination from proceeding. The toxic effects of PCE were incorporated into a model of dehalorespirer growth by adapting the transformation capacity concept previously applied to describe biomass inactivation by products of cometabolic TCE oxidation. The inactivation growth model was coupled to the Andrews substrate utilization model, which accounts for the self-inhibitory effects of PCE on dechlorination rates, and fit to the experimental data. The importance of incorporating biomass inactivation and self-inhibition effects when modeling reductive dechlorination of high PCE concentrations was demonstrated by comparing the goodness-of-fit of the Andrews biomass inactivation and three alternate models that do capture these factors. The new dehalorespiration model should improve our ability to predict contaminant removal in DNAPL source zones and determine the inoculum size needed to successfully implement bioaugmentation of DNAPL source zones.


Assuntos
Desulfuromonas/metabolismo , Modelos Biológicos , Tetracloroetileno/metabolismo , Poluentes Químicos da Água/metabolismo , Biodegradação Ambiental , Biomassa , Desulfuromonas/efeitos dos fármacos , Desulfuromonas/crescimento & desenvolvimento , Água Doce/química , Halogenação , Cinética , Oxirredução , Microbiologia do Solo , Tetracloroetileno/análise , Tetracloroetileno/toxicidade , Poluentes Químicos da Água/análise , Poluentes Químicos da Água/toxicidade
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