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Biomedical subjects

G Gottschalk

Publications and source records attributed to G Gottschalk.

At least 109 records · Page 6Linked to original sources
PubMed1981

Clostridium aceticum (Wieringa), a microorganism producing acetic acid from molecular hydrogen and carbon dioxide.

Spores of Clostridium aceticum (Wieringa) from 1947 have been revived, and a study for a redescription of this microorganism has been carried out. C. aceticum was Gram negative. The cells were rodshaped and peritrichously flagellated. Round spores were formed in terminal position. The DNA contained 33 mol % guanine plus cytosine. The organism was obligately anaerobic and grew either chemolithotrophically with H2 + CO2 or chemoorganotrophically with compounds such as fructose, L-glutamate, L-malate or pyruvate. H2 and CO2 were converted to acetic acid according to the following equation: 2CO2 + 4H2 leads to CH3COOH + 2H2O The optimal temperature for growth was 30 degrees C. The optimal pH for chemolithotrophic growth was 8.3. The doubling times for chemolithotrophic and chemoorganotrophic growth were 25 and 8 h, respectively.

Acetates↗
PubMed1981

Effect of molecular hydrogen and carbon dioxide on chemo-organotrophic growth of Acetobacterium woodii and Clostridium aceticum.

During growth of Acetobacterium woodii on fructose, glucose or lactate in a medium containing less than 0.04% bicarbonate, molecular hydrogen was evolved up to 0.1 mol per mol of substrate. Under an H2-atmosphere growth of A. woodii with organic substrates was completely inhibited whereas under an H2/CO2-atmosphere rapid growth occurred. Under these conditions H2 + CO2 and the organic substrate were utilized simultaneously indicating that A. woodii was able to grow mixotrophically. Clostridium aceticum differed from A. woodii in that H2 was only evolved in the stationary phase, that the inhibition by H2 was observed at pH 8.5 but not at pH 7.5, anf that in the presence of fructose and H2 + CO2 only fructose was utilized. The hydrogenase activity of fructose-grown cells of C. aceticum amounted to only 12% of that of H2 + CO2-grown cells. With A. woodii a corresponding decrease of the activity of this enzyme was not observed.

Acetates↗
PubMed1981

Formation of N,N-Dimethylglycine, Acetic Acid, and Butyric Acid from Betaine by Eubacterium limosum.

Two bacterial strains that grow anaerobically on betaine were isolated from enrichment cultures and identified as strains of Eubacterium limosum. In a mineral medium supplemented with yeast extract and Casitone, the doubling time of E. limosum strain 11A on betaine was 6 h at 37 degrees C. The molar growth yield amounted to 9 g of dry cell mass per mol. Betaine was fermented in accordance with the following equation: 7 betaine + 2 CO(2) --> 7 N,N-dimethylglycine + 1.5 acetate + 1.5 butyrate. E. limosum also grew on methanol and choline. The former was converted to acetate and butyrate, and the latter was converted to N,N-dimethylethanolamine, acetate, and butyrate. The conditions for the quantitative determination of N,N-dimethylglycine by capillary tube isotachophoresis have been determined.

Journal Article↗
PubMed1980

Why a co-substrate is required for anaerobic growth of Escherichia coli on citrate.

Citrate was fermented by Escherichia coli if a second substrate, such as glucose, lactose or lactate, was available to the organism. The function of the second substrate was to provide reducing power for the formation of succinate from oxaloacetate. Citrate lyase, malate dehydrogenase, fumarase and fumarate reductase were present in cell extracts of E. coli at high activity. Oxaloacetate decarboxylate could not be detected, and it is assumed that this lack is the reason for the inability of E. coli to grow anaerobically with citrate as the only carbon and energy source.

Anaerobiosis↗
PubMed1980

Citrate lyase deacetylase of Rhodopseudomonas gelatinosa. Isolation of the enzyme and studies on the inhibition by L-glutamate.

Citrate lyase deacetylase or acetyl-S-(acyl-carrier protein) enzyme thioester hydrolase (acetate) (EC 3.1.2-), was purified 3100-fold with a yield of 3.8% from cell extracts of Rhodopseudomonas gelatinosa. The final enzyme preparation gave a single protein band upon polyacrylamide-gel electrophoresis in the absence or in the presence of sodium dodecylsulfate. The molecular weight of the native enzyme was estimated by gel filtration to be 14 300 +/- 1000. Sodium dodecylsulfate/polyacrylamide gel electrophoresis yielded a molecular weight of 7300 +/- 600 indicating that the enzyme consisted of two subunits. Citrate lyase deacetylase acted as an S-acetyl enzyme thioesterhydrolase because it catalyzed the conversion of citrate lyase (S-acetyl form) into citrate lyase (sulfhydryl form) and acetate. Citrate lyase deacetylase was strongly inhibited by L-glutamate. The half-maximal inhibitor concentration was 7.5 X 10(-4) M. and a Ki-value of 1.2 X 10(-4) M was determined. The mode of inhibition appeared to be of the linear mixed type. L-Glutamate was bound by citrate lyase deacetylase but not by citrate lyase. The pool concentrations of L-glutamate in R. gelatinosa were 10 mM when citrate was present in substrate amounts and 2.7 mM after total consumption of citrate. Simulation of conditions in vivo using homogeneous enzyme preparations of citrate lyase and citrate lyase deacetylase, and glutamate concentrations of 10 mM and 2.7 mM respectively, revealed that the rate of citrate lyase inactivation increased from 8% within 15 min during growth on citrate to 50% within 15 min in the absence of citrate.

Glutamates↗
PubMed1979

Enumeration of bacteria forming acetate from H2 and CO2 in anaerobic habitats.

A method has been worked out that allows the detection and isolation of bacteria fermenting molecular hydrogen and carbon dioxide to acetic acid. The ratio of methanogenic to acetogenic bacteria in sludge and lake sediment samples has been found to be approximately 100 to 1. Acetogenic bacteria could not be detected in rumen samples.

Acetates↗
PubMed1979

Utilization of trimethylamine and other N-methyl compounds for growth and methane formation by Methanosarcina barkeri.

A number of N-methyl compounds, including several methylamines, creatine, sarcosine, choline, and betaine, were readily fermented by enrichment cultures yielding methane as a major product. Methylamine, dimethylamine, trimethylamine, and ethyldimethylamine were fermented by pure cultures of Methanosarcina barkeri; except for ethyldimethylamine, these amines are considered important substrates of this methanogenic microorganism. Creatine, sarcosine, choline, and betaine were fermented to methane only by mixed cultures. During growth of M. barkeri on methyl-, dimethyl-, or trimethylamine, methanol was not excreted into the medium. The fermentation of trimethylamine gave rise to an intermediary accumulation of methyl- and dimethylamine in the medium. An accumulation of methylamine during the fermentation of dimethylamine was not observed. Methane and ammonia were produced from the three methylamines by M. barkeri in amounts expected on the basis of the appropriate fermentation equations. The growth yield was 5.8 mg of cells (dry weight) per mmol of methane and was not dependent on the kind of methyl compound used as substrate.

Euryarchaeota↗
PubMed1978

Fumarate reductase of Clostridium formicoaceticum. A peripheral membrane protein.

When Clostridium formicoaceticum was grown on fumarate or L-malate crude cell extracts contained a high fumarate reductase activity. Using reduced methyl viologen as electron donor the specific activity amounted to 2-3.5 U per mg of protein. Reduced benzyl viologen, FMNH2 and NADH could also serve as electron donors but the specific activities were much lower. The NADH-dependent activity was strictly membrane-bound and rather labile. Its specific activity did not exceed 0.08 U per mg of particle protein. Fumarate reductase activity was also found in cells of C. formicoaceticum grown on fructose, gluconate, glutamate and some other substrates. The methyl viologen-dependent fumarate reductase activity could almost completely be measured with intact cells whereas only about 25% of the cytoplasmic acetate kinase activity was detected with cell suspensions. The preparation of spheroplasts from cells of C. formicoaceticum in 20 mM HEPES-KOH buffer containing 0.6 M sucrose and 1 mM dithioerythritol resulted in the specific release of 88% of the fumarate reductase activity into the spheroplast medium. Only small amounts of the cytoplasmic proteins malic enzyme and acetate kinase were released during this procedure. There results indicate a peripheral location of the fumarate reductase of C. formicoaceticum on the membrane.

Acetate Kinase↗
PubMed1978

Cell yields of Escherichia coli during anaerobic growth on fumarate and molecular hydrogen.

Escherichia coli was grown anaerobically on sodium fumarate and molecular hydrogen or sodium formate in continuous culture. The maximal growth yield and the maintenance coefficient were determined. In a mineral medium a Ymax(fum) value of 6.6 g dry weight per mol fumarate was found. This value increased to 7;5 when casamino acids were present in the medium. From these data and the corresponding Ymax(ATP) values it could be calculated that per mol of fumarate reduced, 0;4 mol of ATP became available for growth. In batch culture a Yfum value of 4.8 g dry weight per mol fumarate was determined.

Adenosine Triphosphate↗
PubMed1978

Fermentation of fumarate and L-malate by Clostridium formicoaceticum.

The fermentation of fumarate and L-malate by Clostridium formicoaceticum was investigated. Growing and nongrowing cells degraded fumarate by dismutation to succinate, acetate, and CO2; on the other hand, only small amounts of succinate were detected when the organism was grown on L-malate. This dicarboxylic acid was mainly converted to acetate and CO2. The fermentation balances were modified if bicarbonate or formate were present in the medium. When C. formicoaceticum was grown in the presence of both dicarboxylic acids, fumarate was consumed before L-malate. The latter was mainly converted to acetate, whereas fumarate was fermented to acetate and succinate. Molar growth yields were determined to be 6 g of dry weight per mol of fumarate and 8 g of dry weight per mol of L-malate fermented.

Acetates↗
PubMed1978

Pathway of succinate and propionate formation in Bacteroides fragilis.

Cell suspensions of Bacteroides fragilis were allowed to ferment glucose and lactate labeled with (14)C in different positions. The fermentation products, propionate and acetate, were isolated, and the distribution of radioactivity was determined. An analysis of key enzymes of possible pathways was also made. The results of the labeling experiments showed that: (i) B. fragilis ferments glucose via the Embden-Meyerhof pathway; and (ii) there was a randomization of carbons 1, 2, and 6 of glucose during conversion to propionate, which is in accordance with propionate formation via fumarate and succinate. The enzymes 6-phosphofrucktokinase (pyrophosphate-dependent), fructose-1,6-diphosphate aldolase, phosphoenolpyruvate carboxykinase, malate dehydrogenase, fumarate reductase, and methylmalonyl-coenzyme A mutase could be demonstrated in cell extracts. Their presence supported the labeling results and suggested that propionate is formed from succinate via succinyl-, methylmalonyl-, and propionyl-coenzyme A. From the results it also is clear that CO(2) is necessary for growth because it is needed for the formation of C4 acids. There was also a randomization of carbons 1, 2, and 6 of glucose during conversion to acetate, which indicated that pyruvate kinase played a minor role in pyruvate formation from phosphoenolpyruvate. Phosphoenolpyruvate carboxykinase, oxaloacetate decarboxylase, and malic enzyme (nicotinamide adenine dinucleotide phosphate-dependent) were present in cell extracts of B. fragilis, and the results of the labeling experiments agreed with pyruvate synthesis via oxaloacetate and malate if these acids are in equilibrium with fumarate. The conversion of [2-(14)C]- and [3-(14)C]lactate to acetate was not associated with a randomization of radioactivity.

Acetates↗
PubMed1977

Purification and properties of citrate lyase ligase from Streptococcus diacetilactis.

Citrate lyase ligase (acetate: SH--[acyl-carrier protein] enzyme ligase (AMP) from Streptococcus diacetilactis was purified 920-fold with a yield of 6.3%. The molecular weight of the enzyme was estimated to be 41000; the ligase consisted of one polypeptide chain. The acetylation of 1 mol of deacetyl-citrate lyase to enzymatically active citrate lyase required 6 mol ATP. The formation of AMP and pyrophosphate in the acetylation reaction was demonstrated. Citrate lyase ligase was specific for the lyase from S. diacetilacitis and did not acetylate lyases from Rhodopseudomonas gelatinosa and Enterobacter aerogenes. The substract acetate and ATP could be replaced by propionate and dATP, repectively. The reaction rates for ATP, acetate and deacetyl-citrate lyase followed Michaelis-Menten kinetics (Km values: 26 micron for ATP, 25 mM for acetate and 38 nM for deacetyl-citrate lyase).

Citrates↗