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A J Stams

Publications and source records attributed to A J Stams.

At least 19 recordsLinked to original sources
PubMed2001

Arginine catabolism by Thermanaerovibrio acidaminovorans.

The arginine catabolism of Thermanaerovibrio acidaminovorans was investigated. T. acidaminovorans was able to produce approximately 0.4--0.5 mol citrulline and 0.5--0.6 mol ornithine from 1 mol of arginine. However, in a methanogenic coculture with Methanobacterium thermoautotrophicum Z245 1 mol arginine was converted to approximately 1 mol of propionate, 0.5 mol acetate, 4 mol ammonia and 4 mol hydrogen; citrulline and ornithine were not formed. Enzyme measurements indicated the presence of the arginine deiminase pathway (ADI) in cells of T. acidaminovorans growing on arginine.

Acetates↗
PubMed2001

A Desulfitobacterium strain isolated from human feces that does not dechlorinate chloroethenes or chlorophenols.

An anaerobic bacterium, strain DP7, was isolated from human feces in mineral medium with formate and 0.02% yeast extract as energy and carbon source. This rod-shaped motile bacterium used pyruvate, lactate, formate, hydrogen, butyrate, and ethanol as electron donor for sulfite reduction. Other electron acceptors such as thiosulfate, nitrate and fumarate stimulated growth in the presence of 0.02% yeast extract and formate. Acetate was the only product during fermentative growth on pyruvate. Six mol of pyruvate were fermented to 7 mol of acetate. 13C-NMR labeling experiments showed homoacetogenic 13C-CO2 incorporation into acetate. The pH and temperature optimum of fermentative growth on pyruvate was 7.4 and 37 degrees C, respectively. The growth rate under these conditions was approximately 0.10 h(-1). Strain DP7 was identified as a new strain of Desulfitobacterium frappieri on the basis of 16S rRNA sequence analysis (99% similarity) and DNA-DNA hybridization (reassociation value of 83%) with Desulfitobacterium frappieri TCE1. In contrast to described Desulfitobacterium strains, the newly isolated strain has not been isolated from a polluted environment and did not use chloroethenes or chlorophenols as electron acceptor.

Bacteria, Anaerobic↗
PubMed2001

Elucidation of the pathways of catabolic glutamate conversion in three thermophilic anaerobic bacteria.

The glutamate catabolism of three thermophilic syntrophic anaerobes was compared based on the combined use of [(13)C] glutamate NMR measurements and enzyme activity determinations. In some cases the uptake of intermediates from different pathways was studied. The three organisms, Caloramator coolhaasii, Thermanaerovibrio acidaminovorans and strain TGO, had a different stoichiometry of glutamate conversion and were dependent on the presence of a hydrogen scavenger (Methanobacterium thermoautotrophicum Z245) to a different degree for their growth. C. coolhaasii formed acetate, CO(2), NH(4)(+) and H(2) from glutamate. Acetate was found to be formed through the beta-methylaspartate pathway in pure culture as well as in coculture. T. acidaminovorans converted glutamate to acetate, propionate, CO(2), NH(4)(+) and H(2). Most likely, this organism uses the beta-methylaspartate pathway for acetate formation. Propionate formation occurred through a direct oxidation of glutamate via succinyl-CoA and methylmalonyl-CoA. The metabolism of T. acidaminovorans shifted in favour of propionate formation when grown in coculture with the methanogen, but this did not lead to the use of a different glutamate degradation pathway. Strain TGO, an obligate syntrophic glutamate-degrading organism, formed propionate, traces of succinate, CO(2), NH(4)(+) and H(2). Glutamate was converted to propionate oxidatively via the intermediates succinyl-CoA and methylmalonyl-CoA. A minor part of the succinyl-CoA was converted to succinate and excreted.

Anaerobiosis↗
PubMed2001

Two distinct enzyme systems are responsible for tetrachloroethene and chlorophenol reductive dehalogenation in Desulfitobacterium strain PCE1.

Desulfitobacterium strain PCE1 is able to use tetrachloroethene and chloroaromatics as terminal electron acceptors for growth. Cell extracts of Desulfitobacterium strain PCE1 grown with tetrachloroethene as electron acceptor showed no dehalogenase activity with 3-chloro-4-hydroxyphenylacetate (Cl-OH-phenylacetate) and other ortho-chlorophenolic compounds in an in vitro assay. Extracts of cells that were grown with Cl-OH-phenylacetate as electron acceptor dechlorinated tetrachloroethene at 10% of the dechlorination rate of Cl-OH-phenylacetate. In both cell extracts dechlorination was inhibited by the addition of 1-iodopropane and dinitrogen oxide, inhibitors of cobalamin-containing enzymes. The enzymes responsible for tetrachloroethene and Cl-OH-phenylacetate dechlorination were partially purified. A 100-fold enriched fraction of chlorophenol reductive dehalogenase was obtained that mainly contained a protein with a subunit size of 48 kDa. The characteristics of this enzyme are similar to that of the chlorophenol reductive dehalogenase of D. dehalogenans. After partial purification of the tetrachloroethene reductive dehalogenase, a fraction was obtained that also contained a 48-kDa protein, but the N-terminal sequence showed no similarity with that of the chlorophenol reductive dehalogenase sequence or with the N-terminal amino acid sequence of tetra- and trichloroethene reductive dehalogenase of Desulfitobacterium strain TCE1. These results provide strong evidence that two different enzymes are responsible for tetrachloroethene and chlorophenol dechlorination in Desulfitobacterium strain PCE1. Furthermore, the characterization of partially purified tetrachloroethene reductive dehalogenase indicated that this enzyme is a novel type of reductive dehalogenase.

Amino Acid Sequence↗
PubMed2001

Constitutive dechlorination of chlorinated ethenes by a methanol degrading methanogenic consortium.

The ability of granular methanogenic sludge to dechlorinate chloroethenes was investigated with unadapted sludge from an upflow anaerobic sludge blanket (UASB) reactor fed with methanol. The sludge degraded chlorinated ethenes, but the degradation rates were low. The addition of primary substrate was necessary to sustain dechlorination. The dechlorinating activity seemed to be constitutively present in the anaerobic bacteria. Usually, one chlorine atom was removed via reductive hydrogenolysis. Only trichloroethene (TCE) was converted to substantial amounts of vinylchloride (VC). 1,1-Dichloroethene (1,1DCE) was observed to be an important intermediate in the dechlorination by unadapted granular sludge, although previously this compound had not been commonly observed. Furthermore, the dechlorination of 1,1DCE was faster than the dechlorination of the other chloroethenes.

Anaerobiosis↗
PubMed2001

Pathway of propionate oxidation by a syntrophic culture of Smithella propionica and Methanospirillum hungatei.

The pathway of propionate conversion in a syntrophic coculture of Smithella propionica and Methanospirillum hungatei JF1 was investigated by (13)C-NMR spectroscopy. Cocultures produced acetate and butyrate from propionate. [3-(13)C]propionate was converted to [2-(13)C]acetate, with no [1-(13)C]acetate formed. Butyrate from [3-(13)C]propionate was labeled at the C2 and C4 positions in a ratio of about 1:1.5. Double-labeled propionate (2,3-(13)C) yielded not only double-labeled acetate but also single-labeled acetate at the C1 or C2 position. Most butyrate formed from [2,3-(13)C]propionate was also double labeled in either the C1 and C2 atoms or the C3 and C4 atoms in a ratio of about 1:1.5. Smaller amounts of single-labeled butyrate and other combinations were also produced. 1-(13)C-labeled propionate yielded both [1-(13)C]acetate and [2-(13)C]acetate. When (13)C-labeled bicarbonate was present, label was not incorporated into acetate, propionate, or butyrate. In each of the incubations described above, (13)C was never recovered in bicarbonate or methane. These results indicate that S. propionica does not degrade propionate via the methyl-malonyl-coenzyme A (CoA) pathway or any other of the known pathways, such as the acryloyl-CoA pathway or the reductive carboxylation pathway. Our results strongly suggest that propionate is dismutated to acetate and butyrate via a six-carbon intermediate.

Bacteria, Anaerobic↗
PubMed2001

Energy yield of respiration on chloroaromatic compounds in Desulfitobacterium dehalogenans.

The amount of energy that can be conserved via halorespiration by Desulfitobacterium dehalogenans JW/IU-DC1 was determined by comparison of the growth yields of cells grown with 3-chloro-4-hydroxyphenyl acetate (Cl-OHPA) and different electron donors. Cultures that were grown with lactate, pyruvate, formate, or hydrogen as an electron donor and Cl-OHPA as an electron acceptor yielded 3.1, 6.6, 1.6, and 1.6 g (dry weight) per mol of reduction equivalents, respectively. Fermentative growth on pyruvate yielded 14 g (dry weight) per mol of pyruvate oxidized. Pyruvate was not fermented stoichiometrically to acetate and lactate, but an excess of acetate was produced. Experiments with 13C-labeled bicarbonate showed that during pyruvate fermentation, approximately 9% of the acetate was formed from the reduction of CO2. Comparison of the growth yields suggests that 1 mol of ATP is produced per mol of acetate produced by substrate-level phosphorylation and that there is no contribution of electron transport phosphorylation when D. dehalogenans grows on lactate plus Cl-OHPA or pyruvate plus Cl-OHPA. Furthermore, the growth yields indicate that approximately 1/3 mol of ATP is conserved per mol of Cl-OHPA reduced in cultures grown in formate plus Cl-OHPA and hydrogen plus Cl-OHPA. Because neither formate nor hydrogen nor Cl-OHPA supports substrate-level phosphorylation, energy must be conserved through the establishment of a proton motive force. Pyruvate ferredoxin oxidoreductase, lactate dehydrogenase, formate dehydrogenase, and hydrogenase were localized by in vitro assays with membrane-impermeable electron acceptors and donors. The orientation of chlorophenol-reductive dehalogenase in the cytoplasmic membrane, however, could not be determined. A model is proposed, which may explain the topology analyses as well as the results obtained in the yield study.

Bacteria, Anaerobic↗
PubMed2001

ADP-dependent phosphofructokinases in mesophilic and thermophilic methanogenic archaea.

Phosphofructokinase (PFK) is a key enzyme of the glycolytic pathway in all domains of life. Two related PFKs, ATP-dependent and PP(i)-dependent PFK, have been distinguished in bacteria and eucarya, as well as in some archaea. Hyperthermophilic archaea of the order Thermococcales, including Pyrococcus and Thermococcus spp., have recently been demonstrated to possess a unique ADP-dependent PFK (ADP-PFK) that appears to be phylogenetically distinct. Here, we report the presence of ADP-PFKs in glycogen-producing members of the orders Methanococcales and Methanosarcinales, including both mesophilic and thermophilic representatives. To verify the substrate specificities of the methanogenic kinases, the gene encoding the ADP-PFK from Methanococcus jannaschii was functionally expressed in Escherichia coli, and the produced enzyme was purified and characterized in detail. Compared to its counterparts from the two members of the order Thermococcales, the M. jannaschii ADP-PFK has an extremely low K(m) for fructose 6-phosphate (9.6 microM), and it accepts both ADP and acetyl-phosphate as phosphoryl donors. Phylogenetic analysis of the ADP-PFK reveals it to be a key enzyme of the modified Embden-Meyerhof pathway of heterotrophic and chemolithoautotrophic archaea. Interestingly, uncharacterized homologs of this unusual kinase are present in several eucarya.

Amino Acid Sequence↗
PubMed2001

New developments in reactor and process technology for sulfate reduction.

Sulfate reduction has been regarded in the past as an unwanted process in anaerobic treatment of sulfate-rich wastewaters. Research efforts were primarily focused on H2S toxicity, competition between sulfidogenic and methanogenic microorganisms and suppression of sulfidogenesis. More recently, the potential sulfidogenesis for treating a wide range of wastestreams contaminated with oxidized sulfurous compounds and/or heavy metals was also appreciated. Heavy metals can be removed by the formation and subsequent precipitation of poorly soluble metal sulfides. Basically two approaches can be distinguished in wastewater treatment: passive treatment using low-cost technologies and active treatment in newly developed bioreactors. Both strategies are discussed.

Bioreactors↗
PubMed2001

Methanol conversion in high-rate anaerobic reactors.

An overview on methanol conversion in high-rate anaerobic reactors is presented, with the focus on technological as well as microbiological aspects. The simple C1-compound methanol can be degraded anaerobically in a complex way, in which methanogens, sulfate reducing bacteria and homoacetogens interact cooperatively or competitively at substrate level. This interaction has large technological implications as it determines the final product of methanol mineralization, methane or carbon dioxide. The degradation route of methanol may be entirely different when environmental conditions change. Direct methanogenesis from methanol seems the predominant mineralization route under mesophilic conditions both in the absence and the presence of sulfate. Under thermophilic conditions methanol oxidation to carbon dioxide and hydrogen appears to play an important role. The UASB technology for mesophilic digestion of methanolic waste has presently reached full-scale maturity. The potential of methanol as feedstock for anaerobic processes is discussed.

Bacteria, Anaerobic↗
PubMed2000

Kinetics of syntrophic cultures: a theoretical treatise on butyrate fermentation.

Numerous microbial conversions in methanogenic environments proceed at (Gibbs) free energy changes close to thermodynamic equilibrium. In this paper we attempt to describe the consequences of this thermodynamic boundary condition on the kinetics of anaerobic conversions in methanogenic environments. The anaerobic fermentation of butyrate is used as an example. Based on a simple metabolic network stoichiometry, the free energy change based balances in the cell, and the flux of substrates and products in the catabolic and anabolic reactions are coupled. In butyrate oxidation, a mechanism of ATP-dependent reversed electron transfer has been proposed to drive the unfavorable oxidation of butyryl-CoA to crotonyl-CoA. A major assumption in our model is that ATP-consumption and electron translocation across the cytoplasmic membrane do not proceed according to a fixed stoichiometry, but depend on the cellular concentration ratio of ATP and ADP. The energetic and kinetic impact of product inhibition by acetate and hydrogen are described. A major consequence of the derived model is that Monod-based kinetic description of this type of conversions is not feasible, because substrate conversion and biomass growth are proposed to be uncoupled. It furthermore suggests that the specific substrate conversion rate cannot be described as a single function of the driving force of the catabolic reaction but depends on the actual substrate and product concentrations. By using nonfixed stoichiometries for the membrane associated processes, the required flexibility of anaerobic bacteria to adapt to varying environmental conditions can be described.

Anaerobiosis↗
PubMed2000

Thermophilic sulfate reduction and methanogenesis with methanol in a high rate anaerobic reactor.

Sulfate reduction outcompeted methanogenesis at 65 degrees C and pH 7.5 in methanol and sulfate-fed expanded granular sludge bed reactors operated at hydraulic retention times (HRT) of 14 and 3.5 h, both under methanol-limiting and methanol-overloading conditions. After 100 and 50 days for the reactors operated at 14 and 3.5 h, respectively, sulfide production accounted for 80% of the methanol-COD consumed by the sludge. The specific methanogenic activity on methanol of the sludge from a reactor operated at HRTs of down to 3.5 h for a period of 4 months gradually decreased from 0. 83 gCOD. gVSS(-1). day(-1) at the start to a value of less than 0.05 gCOD. gVSS(-1). day(-1), showing that the relative number of methanogens decreased and eventually became very low. By contrast, the increase of the specific sulfidogenic activity of sludge from 0. 22 gCOD. gVSS(-1). day(-1) to a final value of 1.05 gCOD. gVSS(-1). day(-1) showed that sulfate reducing bacteria were enriched. Methanol degradation by a methanogenic culture obtained from a reactor by serial dilution of the sludge was inhibited in the presence of vancomycin, indicating that methanogenesis directly from methanol was not important. H(2)/CO(2) and formate, but not acetate, were degraded to methane in the presence of vancomycin. These results indicated that methanol degradation to methane occurs via the intermediates H(2)/CO(2) and formate. The high and low specific methanogenic activity of sludge on H(2)/CO(2) and formate, respectively, indicated that the former substrate probably acts as the main electron donor for the methanogens during methanol degradation. As sulfate reduction in the sludge was also strongly supported by hydrogen, competition between sulfate reducing bacteria and methanogens in the sludge seemed to be mainly for this substrate. Sulfate elimination rates of up to 15 gSO(4)(2-)/L per day were achieved in the reactors. Biomass retention limited the sulfate elimination rate.

Acetates↗
PubMed2000

Denitrification with methane as electron donor in oxygen-limited bioreactors.

The microbial population from a reactor using methane as electron donor for denitrification under microaerophilic conditions was analyzed. High numbers of aerobic methanotrophic bacteria (3 10(7) cells/ml) and high numbers of acetate-utilizing denitrifying bacteria (2 10(7) cells/ml) were detected, but only very low numbers of methanol-degrading denitrifying bacteria (4 10(4) cells/ml) were counted. Two abundant acetate-degrading denitrifiers were isolated which, based on 16S rRNA analysis, were closely related to Mesorhizobium plurifarium (98.4% sequence similarity) and a Stenotrophomonas sp. (99.1% sequence similarity). A methanol-degrading denitrifying bacterium isolated from the bioreactor morphologically resembled Hyphomicrobium sp. and was moderately related to H. vulgare (93.5% sequence similarity). The initial characterization of the most abundant methanotrophic bacterium indicated that it belongs to class II of the methanotrophs. "In vivo" 13C-NMR with concentrated cell suspensions showed that this methanotroph produced acetate under oxygen limitation. The microbial composition of reactor material together with the NMR experiments suggest that in the reactor methanotrophs excrete acetate, which serves as the direct electron donor for denitrification.

Anaerobiosis↗
PubMed2000

Performance of a thermophilic sulfate and sulfite reducing high rate anaerobic reactor fed with methanol.

Thermophilic sulfate and sulfite reduction was studied in lab-scale Expanded Granular Sludge Bed (EGSB) reactors operated at 65 degrees C and pH 7.5 with methanol as the sole carbon and energy source for the sulfate- and sulfite-reducing bacteria. At a hydraulic retention time (HRT) of 10 h, maximum sulfite and sulfate elimination rates of 5.5 g SO3(2-) L(-1) day(-1) (100% elimination) and 5.7 g SO4(2-) L(-1) day(-1) (55% elimination) were achieved, resulting in an effluent sulfide concentration of approximately 1800 mg S L(-1). Sulfate elimination was limited by the sulfide concentration, as stripping of H2S from the reactor with nitrogen gas was found to increase the sulfate elimination rate to 9.9 g SO4(2-) L(-1) day(-1) (100% elimination). At a HRT of 3 h, maximum achievable sulfite and sulfate elimination rates were even 18 g SO3(2-) L(-1) day(-1) (100% elimination) and 11 g SO4(2-) L(-1) day(-1) (50% elimination). At a HRT of 3 h, the elimination rate was limited by the biomass retention of the system. 5.5 +/- 1.8% of the consumed methanol was converted to acetate, which was not further degraded by sulfate reducing bacteria present in the sludge. The acetotrophic activity of the sludge could not be stimulated by cultivating the sludge for 30 days under methanol-limiting conditions. Omitting cobalt as trace element from the influent resulted in a lower acetate production rate, but it also led to a lower sulfate reduction rate. Sulfate degradation in the reactor could be described by zeroth order kinetics down to a threshold concentration of 0.05 g L(-1), while methanol degradation followed Michaelis-Menten kinetics with a Km of 0.037 g COD L(-1).

Anaerobiosis↗
PubMed2000

Caloramator coolhaasii sp. nov., a glutamate-degrading, moderately thermophilic anaerobe.

An obligately anaerobic, moderately thermophilic, glutamate-degrading bacterium (strain ZT) was isolated from an enrichment culture obtained from anaerobic thermophilic granular sludge. The cells were rod-shaped to filamentous and showed no motility or spore formation. The cell wall had a Gram-positive structure, which was revealed by electron microscopy. Optimum growth of the strain was observed under neutrophilic conditions at 50-55 degrees C. The doubling time of strain ZT grown in rich medium was approximately 1 h at optimal pH and temperature. Strain ZT was able to grow on a variety of organic compounds. Most carbon sources were converted to acetate, CO2, H2, and traces of propionate and lactate. Strain ZT oxidized glutamate to acetate, CO2, NH4+, traces of propionate and H2. The doubling time on this substrate was 1-6 d. The strain fermented glutamate syntrophically in co-culture with Methanobacterium thermoautotrophicum Z-245T to the same products, but the co-culture had a fourfold higher growth rate. 16S rDNA sequence analysis revealed a relationship with Thermobrachium celere, Caloramator indicus and Caloramator proteoclasticus. The G+C content was 31.7 mol%. Based on its morphological, phylogenetic and physiological characteristics, it is proposed that strain ZT should be classified in the genus Caloramator as a new species, Caloramator coolhaasii.

Bacteria, Anaerobic↗
PubMed1999

Molecular and biochemical characterization of the ADP-dependent phosphofructokinase from the hyperthermophilic archaeon Pyrococcus furiosus.

Pyrococcus furiosus uses a modified Embden-Meyerhof pathway involving two ADP-dependent kinases. Using the N-terminal amino acid sequence of the previously purified ADP-dependent glucokinase, the corresponding gene as well as a related open reading frame were detected in the genome of P. furiosus. Both genes were successfully cloned and expressed in Escherichia coli, yielding highly thermoactive ADP-dependent glucokinase and phosphofructokinase. The deduced amino acid sequences of both kinases were 21.1% identical but did not reveal significant homology with those of other known sugar kinases. The ADP-dependent phosphofructokinase was purified and characterized. The oxygen-stable protein had a native molecular mass of approximately 180 kDa and was composed of four identical 52-kDa subunits. It had a specific activity of 88 units/mg at 50 degrees C and a pH optimum of 6.5. As phosphoryl group donor, ADP could be replaced by GDP, ATP, and GTP to a limited extent. The K(m) values for fructose 6-phosphate and ADP were 2.3 and 0.11 mM, respectively. The phosphofructokinase did not catalyze the reverse reaction, nor was it regulated by any of the known allosteric modulators of ATP-dependent phosphofructokinases. ATP and AMP were identified as competitive inhibitors of the phosphofructokinase, raising the K(m) for ADP to 0.34 and 0.41 mM, respectively.

Adenosine Diphosphate↗
PubMed1999

Purification and molecular characterization of ortho-chlorophenol reductive dehalogenase, a key enzyme of halorespiration in Desulfitobacterium dehalogenans.

ortho-Chlorophenol reductive dehalogenase of the halorespiring Gram-positive Desulfitobacterium dehalogenans was purified 90-fold to apparent homogeneity. The purified dehalogenase catalyzed the reductive removal of a halogen atom from the ortho position of 3-chloro-4-hydroxyphenylacetate, 2-chlorophenol, 2,3-dichlorophenol, 2,4-dichlorophenol, 2,6-dichlorophenol, pentachlorophenol, and 2-bromo-4-chlorophenol with reduced methyl viologen as electron donor. The dechlorination of 3-chloro-4-hydroxyphenylacetate was catalyzed by the enzyme at a Vmax of 28 units/mg protein and a Km of 20 microM. The pH and temperature optimum were 8.2 and 52 degrees C, respectively. EPR analysis indicated one [4Fe-4S] cluster (midpoint redox potential (Em) = -440 mV), one [3Fe-4S] cluster (Em = +70 mV), and one cobalamin per 48-kDa monomer. The Co(I)/Co(II) transition had an Em of -370 mV. Via a reversed genetic approach based on the N-terminal sequence, the corresponding gene was isolated from a D. dehalogenans genomic library, cloned, and sequenced. This revealed the presence of two closely linked genes: (i) cprA, encoding the o-chlorophenol reductive dehalogenase, which contains a twin-arginine type signal sequence that is processed in the purified enzyme; (ii) cprB, coding for an integral membrane protein that could act as a membrane anchor of the dehalogenase. This first biochemical and molecular characterization of a chlorophenol reductive dehalogenase has revealed structural resemblance with haloalkene reductive dehalogenases.

Amino Acid Sequence↗