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21.
Melike Balk Hans G. H. J. Heilig Miriam H. A. van Eekert Alfons J. M. Stams Irene C. Rijpstra Jaap S. Sinninghe-Damsté Willem M. de Vos Servé W. M. Kengen 《Extremophiles : life under extreme conditions》2009,13(6):885-894
A novel anaerobic, thermophilic, Gram-positive, spore-forming, and sugar-fermenting bacterium (strain TLO) was isolated from
a geothermal spring in Ayaş, Turkey. The cells were straight to curved rods, 0.4–0.6 μm in diameter and 3.5–10 μm in length.
Spores were terminal and round. The temperature range for growth was 40–80°C, with an optimum at 70°C. The pH optimum was
between 6.3 and 6.8. Strain TLO has the capability to ferment a wide variety of mono-, di-, and polysaccharides and proteinaceous
substrates, producing mainly lactate, next to acetate, ethanol, alanine, H2, and CO2. Remarkably, the bacterium was able to grow in an atmosphere of up to 25% of CO as sole electron donor. CO oxidation was
coupled to H2 and CO2 formation. The G + C content of the genomic DNA was 35.1 mol%. Based on 16S rRNA gene sequence analysis and the DNA–DNA hybridization
data, this bacterium is most closely related to Thermoanaerobacter thermohydrosulfuricus and Thermoanaerobacter siderophilus (99% similarity for both). However, strain TLO differs from Thermoanaerobacter thermohydrosulfuricus in important aspects, such as CO-utilization and lipid composition. These differences led us to propose that strain TLO represents
a subspecies of Thermoanaerobacter thermohydrosulfuricus, and we therefore name it Thermoanaerobacter thermohydrosulfuricus subsp. carboxydovorans. 相似文献
22.
Detection and localization of syntrophic propionate-oxidizing bacteria in granular sludge by in situ hybridization using 16S rRNA-based oligonucleotide probes. 总被引:13,自引:8,他引:5
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H J Harmsen H M Kengen A D Akkermans A J Stams W M de Vos 《Applied microbiology》1996,62(5):1656-1663
In situ hybridization with fluorescent oligonucleotides was used to detect and localize microorganisms in the granules of two lab-scale upflow anaerobic sludge blanket reactors that had been fed for several months with either sucrose or a mixture of volatile fatty acids. Sections of the granules were hybridized with 16S rRNA-targeted oligonucleotide probes for Bacteria, Archaea, specific phylogenetic groups of methanogens, and two syntrophic propionate-oxidizing strains, MPOB and KOPROP1. Cells of the syntrophic strain KOPROP1 were not detected in either type of sludge granules. Hybridizations of the sucrose-fed granules showed an outer layer of mainly bacterial microcolonies with different morphologies. More inwards of these granules, a layer of different methanogenic microcolonies mixed with large colonies of the syntrophic strain MPOB could be detected. The MPOB colonies were intertwined with hydrogen- or formate-consuming methanogens, indicating their syntrophic growth. The granules fed with volatile fatty acids showed an outer layer of mainly bacteria and then a thick layer of Methanosaeta-like methanogens mixed with a few bacteria and a layer of methanogens mixed with syntrophic MPOB microcolonies. The centers of both sludge types consisted of large cavities and methanogenic microcolonies. These results indicate a juxtapositioning of syntrophic bacteria and methanogens and provide additional evidence for a layered microbial architecture of anaerobic granular sludge. 相似文献
23.
Servé W. M. Kengen Judith J. Mosterd Rob L. H. Nelissen Jan T. Keltjens Chris van der Drift Godfried D. Vogels 《Archives of microbiology》1988,150(4):405-412
The enzymatic conversion of formaldehyde to CH3S-CoM in crude extracts of Methanobacterium thermoautotrophicum was used as a means to investigate the methyl-tetrahydromethanopterin: HS-CoM methyltransferase reaction. All components necessary for formaldehyde conversion were shown to be present in a soluble protein fraction. This soluble cell fraction still contained a major amount of corrinoids. Apart from tetrahydromethanopterin no other soluble cofactors were required for formaldehyde conversion. The dependence of the system on catalytic amounts of ATP was shown to be specific. Several nucleoside triphosphates or ADP were unable to substitute for ATP. Remarkably, various strong reducing systems, especially titanium(III)citrate could replace ATP to a large extent. The ATP-dependent formaldehyde conversion to CH3S-CoM was inhibited in the presence of nitrous oxide, detergents or 2,3-dialdehyde-ATP. The results support a role for a corrinoid protein in the methyl-tetrahydromethanopterin: HS-CoM methyltransferase reaction at which ATP is involved in the activation of this protein, probably in the conversion of inactive B12a or B12r to active B12s.Abbreviations HS-CoM
Coenzyme M, 2-mercaptoethanesulfonate
- CH3S-CoM
methylcoenzyme M, 2-(methylthio)ethanesulfonate
- H4MPT
5,6,7,8-tetrahydromethanopterin
- BES
2-bromoethanesulfonate
- BCE
boiled cell-free extract
- DTT
dithiothreitol
- TCS
3,3,4,5-tetrachlorosalicylanilide
- DNTB
2,2-dinitro-5,5-dithiobenzoic acid
- TES
N-tris(hydroxymethyl)methyl-2-aminoethanesulfonate
- HEPES
N-2-hydroxyethylpiperazine-N-2-ethanesulfonic acid
- PIPES
piperazine-N,N-bis[2-ethanesulfonic acid]
- AMP-PNP
5-adenylyl imidophosphate 相似文献
24.
25.
Carboxylic ester hydrolases from hyperthermophiles 总被引:1,自引:0,他引:1
Mark Levisson John van der Oost Servé W. M. Kengen 《Extremophiles : life under extreme conditions》2009,13(4):567-581
Carboxylic ester hydrolyzing enzymes constitute a large group of enzymes that are able to catalyze the hydrolysis, synthesis
or transesterification of an ester bond. They can be found in all three domains of life, including the group of hyperthermophilic
bacteria and archaea. Esterases from the latter group often exhibit a high intrinsic stability, which makes them of interest
them for various biotechnological applications. In this review, we aim to give an overview of all characterized carboxylic
ester hydrolases from hyperthermophilic microorganisms and provide details on their substrate specificity, kinetics, optimal
catalytic conditions, and stability. Approaches for the discovery of new carboxylic ester hydrolases are described. Special
attention is given to the currently characterized hyperthermophilic enzymes with respect to their biochemical properties,
3D structure, and classification. 相似文献
26.
Suzanne Wolterink-van Loo Marco A. J. Siemerink Georgios Perrakis Thijs Kaper Servé W.M. Kengen John van der Oost 《Archaea (Vancouver, B.C.)》2009,2(4):233-239
Sulfolobus acidocaldarius 2-keto-3-deoxygluconate
aldolase (SacKdgA) displays optimal activity at 95 °C and is
studied as a model enzyme for aldol condensation reactions. For
application of SacKdgA at lower temperatures, a library of randomly
generated mutants was screened for improved synthesis of
2-keto-3-deoxygluconate from pyruvate and glyceraldehyde at the
suboptimal temperature of 50 °C. The single mutant SacKdgA-V193A
displayed a threefold increase in activity compared with wild type
SacKdgA. The increased specific activity at 40–60 °C of
this mutant was observed, not only for the condensation of pyruvate
with glyceraldehyde, but also for several unnatural acceptor
aldehydes. The optimal temperature for activity of SacKdgA-V193A was
lower than for the wild type enzyme, but enzymatic stability of the
mutant was similar to that of the wild type, indicating that activity
and stability were uncoupled. Valine193 has Van der Waals interactions
with Lysine153, which covalently binds the substrate during catalysis.
The mutation V193A introduced space close to this essential residue,
and the increased activity of the mutant presumably resulted from
increased flexibility of Lysine153. The increased activity of
SacKdgA-V193A with unaffected stability demonstrates the potential for
optimizing extremely thermostable aldolases for synthesis reactions at
moderate temperatures. 相似文献
27.
Production and Characterization of a Thermostable Alcohol Dehydrogenase That Belongs to the Aldo-Keto Reductase Superfamily 总被引:2,自引:0,他引:2
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Ronnie Machielsen Agustinus R. Uria Serv W. M. Kengen John van der Oost 《Applied microbiology》2006,72(1):233-238
The gene encoding a novel alcohol dehydrogenase that belongs to the aldo-keto reductase superfamily has been identified in the hyperthermophilic archaeon Pyrococcus furiosus. The gene, referred to as adhD, was functionally expressed in Escherichia coli and subsequently purified to homogeneity. The enzyme has a monomeric conformation with a molecular mass of 32 kDa. The catalytic activity of the enzyme increases up to 100°C, and a half-life value of 130 min at this temperature indicates its high thermostability. AdhD exhibits a broad substrate specificity with, in general, a preference for the reduction of ketones (pH optimum, 6.1) and the oxidation of secondary alcohols (pH optimum, 8.8). Maximal specific activities were detected with 2,3-butanediol (108.3 U/mg) and diacetyl-acetoin (22.5 U/mg) in the oxidative and reductive reactions, respectively. Gas chromatrography analysis indicated that AdhD produced mainly (S)-2-pentanol (enantiomeric excess, 89%) when 2-pentanone was used as substrate. The physiological role of AdhD is discussed. 相似文献
28.
Saloua El Messaoudi Tim H. Schreuder Roel D. Kengen Gerard A. Rongen Petra H. van den Broek Dick H. J. Thijssen Niels P. Riksen 《PloS one》2014,9(4)
Introduction
Large prospective studies in patients with type 2 diabetes mellitus have demonstrated that metformin treatment improves cardiovascular prognosis, independent of glycemic control. Administration of metformin potently limits infarct size in murine models of myocardial infarction. This study examined, for the first time in humans, whether metformin limits ischemia-reperfusion (IR) injury in vivo using a well-validated forearm model of endothelial IR-injury.Methods
Twenty-eight healthy volunteers (age 41±6 years, 10 male/16 female) were randomized between pretreatment with metformin (500 mg three times a day for 3 days) or no treatment in a Prospective Randomized Open Blinded Endpoint study. Brachial artery flow mediated dilation (FMD) was measured before and after 20 minutes of forearm ischemia and 20 minutes of reperfusion. FMD analysis was performed offline by investigators blinded for the treatment arm.Results
Baseline FMD did not differ between metformin pretreatment and no pretreatment (6.9±3.6% and 6.1±3.5%, respectively, p = 0.27, n = 26). FMD was significantly lower after forearm IR in both treatment arms (4.4±3.3% and 4.3±2.8%, respectively, P<0.001 in both conditions). A linear mixed model analysis revealed that metformin treatment did not prevent the decrease in FMD by IR.Conclusion
A 3 day treatment with metformin in healthy, middle-aged subjects does not protect against endothelial IR-injury, measured with brachial artery FMD after forearm ischemia. Further studies are needed to clarify what mechanism underlies the cardiovascular benefit of metformin treatment.Trial Registration
ClinicalTrials.gov NCT01610401相似文献29.
Wolterink AF Schiltz E Hagedoorn PL Hagen WR Kengen SW Stams AJ 《Journal of bacteriology》2003,185(10):3210-3213
A chlorate reductase has been purified from the chlorate-reducing strain Pseudomonas chloritidismutans. Comparison with the periplasmic (per)chlorate reductase of strain GR-1 showed that the cytoplasmic chlorate reductase of P. chloritidismutans reduced only chlorate and bromate. Differences were also found in N-terminal sequences, molecular weight, and subunit composition. Metal analysis and electron paramagnetic resonance measurements showed the presence of iron and molybdenum, which are also found in other dissimilatory oxyanion reductases. 相似文献
30.
Constantinos Patinios Sjoerd C A Creutzburg Adini Q Arifah Beln Adiego-Prez Evans
A Gyimah Colin
J Ingham Serv W M Kengen John van der Oost Raymond H J Staals 《Nucleic acids research》2021,49(19):11392
CRISPR-Cas is a powerful tool for genome editing in bacteria. However, its efficacy is dependent on host factors (such as DNA repair pathways) and/or exogenous expression of recombinases. In this study, we mitigated these constraints by developing a simple and widely applicable genome engineering tool for bacteria which we termed SIBR-Cas (Self-splicing Intron-Based Riboswitch-Cas). SIBR-Cas was generated from a mutant library of the theophylline-dependent self-splicing T4 td intron that allows for tight and inducible control over CRISPR-Cas counter-selection. This control delays CRISPR-Cas counter-selection, granting more time for the editing event (e.g. by homologous recombination) to occur. Without the use of exogenous recombinases, SIBR-Cas was successfully applied to knock-out several genes in three wild-type bacteria species (Escherichia coli MG1655, Pseudomonas putida KT2440 and Flavobacterium IR1) with poor homologous recombination systems. Compared to other genome engineering tools, SIBR-Cas is simple, tightly regulated and widely applicable for most (non-model) bacteria. Furthermore, we propose that SIBR can have a wider application as a simple gene expression and gene regulation control mechanism for any gene or RNA of interest in bacteria. 相似文献