Showing papers by "Alfons J. M. Stams published in 1990"
TL;DR: Although the affinity for acetate was high, the hydrogenotrophic methane bacteria were not able to remove acetate to lower concentrations than the acetoclastic methane bacteria, neither in pure cultures nor in anaerobic granular sludge samples.
Abstract: The minimum threshold concentrations of acetate utilization and the enzymes responsible for acetate activation of several methanogenic bacteria were investigated and compared with literature data. The minimum acetate concentrations reached by hydrogenotrophic methane bacteria, which require acetate as carbon source, were between 0.4 and 0.6 mM. The acetoclastic Methanosarcina achieves acetate concentrations between 0.2 and 1.2 mM and Methanothrix between 7 and 70 μM. For the activation of acetate most of the hydrogenotrophic methane bacteria investigated use an acetyl-CoA synthetase with a relatively low Km (40–90 μM) for acetate. although the affinity for acetate was high, the hydrogenotrophic methane bacteria were not able to remove acetate to lower concentrations than the acetoclastic methane bacteria, neither in pure cultures nor in anaerobic granular sludge samples. Based on these observations, it is not likely that hydrogenotrophic methanogens compete strongly for acetate with the acetoclastic methane bacteria.
161 citations
TL;DR: Most of the enzymes involved in the methylmalonyl- CoA pathway for propionate oxidation, including a propionyl-CoA: oxaloacetate transcarboxylase, were demonstrated in S. wolinii.
Abstract: Enzyme measurements were carried out with crude cell-free extracts of the propionate oxidizing coculture of Syntrophobacter wolinii and Desulfovibrio G11. Using cell-free extracts of a pure culture of Desulfovibrio G11 as a blank, most of the enzymes involved in the methylmalonyl-CoA pathway for propionate oxidation, including a propionyl-CoA: oxaloacetate transcarboxylase, were demonstrated in S. wolinii.
57 citations
TL;DR: Cell suspensions of methanogenic bacteria reductively dechlorinated 1,2-dichloroethane via two reaction-mechanisms and stimulated methanogenesis caused an increase in the amount of dechlorination products formed, whereas the opposite was found when methane formation was inhibited.
Abstract: Concentrated cell suspensions of methanogenic bacteria reductively dechlorinated 1,2-dichloroethane via two reaction-mechanisms: a dihalo-elimination yielding ethylene and two hydrogenolysis reactions yielding chloroethane and ethane, consecutively. The transformation of chloroethane to ethane was inhibited by 1,2-dichloroethane. Stimulation of methanogenesis caused an increase in the amount of dechlorination products formed, whereas the opposite was found when methane formation was inhibited. Cells of Methanosarcina barkeri grown on H2/CO2 converted 1,2-dichloroethane and chloroethane at higher rates than acetate or methanol grown cells.
57 citations
TL;DR: Results show that autotrophic nitrifying bacteria may account for most of the nitrification in the examined soils, and indicate that in the investigated soil heterotrophs are of minor importance in the oxidation of atmospheric ammonium.
Abstract: The role of autotrophic and heterotrophic nitrifying microorganisms in the oxidation of atmospheric ammonium in two acid and one calcareous location of a Dutch woodland area was investigated. In soil slurries nitrate formation was completely inhibited by acetylene, a specific inhibitor of autotrophic ammonium-oxidizing bacteria. A survey of nitrifiers in the forest soils showed that both autotrophic ammonium- and nitrite-oxidizing bacteria were present in high numbers and evidence was obtained that autotrophic bacteria are able to nitrify below pH 4. These results show that autotrophic nitrifying bacteria may account for most of the nitrification in the examined soils. To assess the contribution of heterotrophic nitrifiers, about 200 strains of heterotrophic bacteria and 21 morphologically distinct fungal strains were isolated from the acid soil locations and tested for their ability to nitrify. Only one Penicillium strain produced nitrate in test media, but its nitrate formation when added to acid soils was poor. These findings indicate that in the investigated soil heterotrophs are of minor importance in the oxidation of atmospheric ammonium.
46 citations
TL;DR: The methyl-CoM reductase from Methanothrix soehngenii was purified 18-fold to apparent homogeneity with 50% recovery in three steps with at the optimum pH of 7.0 and 60 nmol of methane were formed per min per mg protein.
Abstract: The methyl-CoM reductase from Methanothrix soehngenii was purified 18-fold to apparent homogeneity with 50% recovery in three steps. The native molecular mass of the enzyme estimated by gel-fitration was 280 kDa. SDS-polyacrylamide gel electrophoresis revealed three protein bands corresponding to M r 63 900, 41 700 and 30 400 Da. The methyl-coenzyme M reductase constitutes up to 10% of the soluble cell protein. The enzyme has K m apparent values of 23 μM and 2 mM for N -7-mercaptoheptanoylthreonine phosphate (HS- HTP = component B ) and methyl-coenzyme M (CH 3 CoM) respectively. At the optimum pH of 7.0 60 nmol of methane were formed per min per mg protein.
28 citations
01 Jan 1990
TL;DR: Interspecies electron transfer is irrefutable associated with methanogenic environments and therefore acetogens are required for the conversion of reduced organic fermentation products to meethanogenic substrates.
Abstract: Interspecies electron transfer is irrefutable associated with methanogenic environments Methanogens can only to use a very limited range of substrates and therefore acetogens are required for the conversion of reduced organic fermentation products (ethanol, lactate, propionate, butyrate etc) to methanogenic substrates The activity of methanogens affects the metabolism of both fermentative and acetogenic bacteria Fermentative organisms which can dispose part of the reducing equivalents as molecular hydrogen, form more oxidized and less reduced organic products in the presence of hydrogen-consuming methanogens On the other hand the degradation of such reduced organic compounds is obligately linked with methanogenesis
20 citations
TL;DR: Vegetation of an acid woodland, receiving an atmospheric ammonium input of about 3 kmol (40 kg N) per hectare per year, was analyzed on the content of organic nitrogen, ammonium and nitrate and a high nitrate content was found in bird-cherry, black-berry and bracken.
Abstract: Vegetation of an acid woodland, receiving an atmospheric ammonium input of about 3 kmol (40 kg N) per hectare per year, was analyzed on the content of organic nitrogen, ammonium and nitrate. A high nitrate content (50–320 μmol g−1 dry weight) was found in bird-cherry, black-berry and bracken, whereas only low amounts (up to 2 μmol g−1 dry weight) of nitrate were present in mountain-ash, hazel and the two dominant tree species oak and birch. The impact of this nitrate uptake and nitrate accumulation on soil pH and autotrophic nitrification is discussed.
19 citations
TL;DR: To determine the fate of atmospheric ammonium in forest soils, one calcareous and two acid forest soils were incubated with 15N ammonium and a large proportion of the 15N was incorporated in organic nitrogen compounds.
Abstract: To determine the fate of atmospheric ammonium in forest soils, one calcareous and two acid forest soils were incubated with 15N ammonium. In the calcareous soil about 65% of the applied 15N-ammonium was recovered as nitrate after 98 days of incubation, whereas in the acid soils less than 10% of the 15N-ammonium was converted to nitrate. In all soils a large proportion of the 15N was incorporated in organic nitrogen compounds. This incorporation limits the use of 15N tracers for the elucidation of the fate of atmospheric ammonium in soils.
13 citations
TL;DR: Soil percolation columns in which a pF of 2 could be maintained were developed and results indicate that autotrophic bacteria from acid soils are sensitive to a pH increase.
Abstract: Soil percolation columns in which a pF of 2 could be maintained were developed to study nitrification in soils and litter of an acid and a calcareous forest soil location. High nitrification rates were observed in the calcareous soil. In the acid soil nitrification was much slower. A column filled with leaf litter gave a low nitrification rate at the start of the experiment, but a high rate was found after 60 days of percolation with an ammonium-containing medium of pH 4. In this leaf litter high numbers of autotrophic bacteria were just present at the beginning of the experiment, whereas at the end only low numbers were detected. Results indicate that autotrophic bacteria from acid soils are sensitive to a pH increase.
13 citations
TL;DR: Asp 66 did not require vitamins and grew well in mineral media with a fermentable substrate and was able to fix N2 as evidenced by its growth with N1 as sole nitrogen source and its ability to reduce acetylene to ethylene.
Abstract: From estuarine mud a rod-shaped, motile, gram-negative, anaerobic bacterium was isolated (strain asp 66). Asp 66 fermented several substrates including glucose, fructose, malate, fumarate, citrate and aspartate. Fermentation products were acetate, propionate and presumably CO2. Hydrogen was never formed nor utilized. Succinate conversion to propionate was catalyzed by cell suspensions but did not support growth. Asp 66 did not require vitamins and grew well in mineral media with a fermentable substrate. The pH range for growth was from 6.5 to 8.5. Temperature optimum was 27 to 30°C. The strain was able to fix N2 as evidenced by its growth with N2 as sole nitrogen source and its ability to reduce acetylene to ethylene. Cell-free extracts of cultures grown under air without shaking contained cytochrome(s) with absorption peaks at 523 nm and at 553 nm. The G+C content of the DNA was 60.8+-1 mol%. The taxonomic position of strain asp 66 is discussed.
8 citations
01 Jan 1990
TL;DR: In vivo high-resolution NMR with the Gram-negative Syntrophobacter wolinii and a Gram-positive syntrophic Propionate oxidizing organism, indicated the involvement of an oxaloacetate: propionyl-CoA transcarboxylase in propionate oxidation.
Abstract: In vivo high-resolution NMR with the Gram-negative Syntrophobacter wolinii and a Gram-positive syntrophic propionate oxidizing organism, indicated the involvement of an oxaloacetate: propionyl-CoA transcarboxylase in propionate oxidation. This finding was confirmed by enzyme measurement in cell-free extracts. Two sulphidogenic cocultures grew at a similar specific growth rate, whereas substitution of the hydrogenotrophic sulphate reducer by methane bacteria resulted in slower growth. The S. wolinii coculture had a lower cell yield than Desulfobulbus propionicus. This difference is explained in terms of energy conservation mechanisms.
01 Jan 1990
01 Jan 1990
TL;DR: Both obligate and facultative proton-reducing anaerobic bacteria are affected by changes in the hydrogen partial pressure and the presence of hydrogenotrophs leads to a shift in fermentation products.
Abstract: Both obligate and facultative proton-reducing anaerobic bacteria are affected by changes in the hydrogen partial pressure. The first group of microorganisms includes mainly acetogenic bacteria which oxidize compounds like ethanol, propionate, butyrate, benzoate or phenol to acetate, (C02) and hydrogen (Dolfing, 1988). These reactions are only feasible at low hydrogen partial pressures and therefore carried out in syntrophy with hydrogenotrophic bacteria. The second group consists of a wide variety of fermentative bacteria able to dispose reducing equivalents as hydrogen or in the form of reduced organic compounds. The presence hydrogenotrophs leads to a shift in fermentation products.