A proposed pathway for catabolism of propionate in methanogenic cocultures.

A metabolic pathway for the catabolism of propionate is proposed. This pathway incorporates a transcarboxylation reaction involving propionyl coenzyme A and oxaloacetate and a carboxylation of pyruvate to regenerate oxaloacetate. Data indicated that the proposed pathway is reversible. The proposed pathway and its apparent reversibility provide a reasonable explanation of observations obtained from metabolism of labeled substrate.

C nuclear magnetic resonance studies of propionate catabolism in methanogenic cocultures.

Propionate catabolism was monitored in anaerobic cocultures of propionate-degrading and methanogenic bacteria. Metabolism was monitored by use of C-enriched propionate and succinate. The intermediates identified indicated that the methylmalonyl coenzyme A pathway was used in these cultures. The data also indicated that a transcarboxylation reaction between succinate and propionyl coenzyme A occurred, yielding propionate and methylmalonyl coenzyme A.

Metabolism of Escherichia coli injured by copper.

Escherichia coli injured by copper in carbonate buffer simulating the drinking water environment showed decreased oxygen utilization. Oxygraph measurements revealed that copper-injured bacteria had a rate of oxygen utilization that was less than 25% of that of control cells. Respirometry experiments measured rates over a longer period of time and showed similar trends. Nuclear magnetic resonance spectroscopy (13C nmr) and gas chromatography were used to identify differences in metabolism between healthy and injured populations of E. coli. The rate of glucose utilization by injured cells under anaerobic conditions was 64% of that of healthy cells. The rates of lactate and ethanol accumulation were 88 and 50% of the control, respectively. The 13C nmr studies of oxygenated cultures revealed differences in the accumulation of acetate and glutamine. Aerobic utilization of glucose and succinate by injured cells were 87 and 21% of the rate of the controls, respectively. Additional studies revealed injured cells had a decreased ability to reduce 2-(p-iodophenyl)-3-(p-nitrophenyl)-5-phenyltetrazolium chloride (INT) with a variety of carbohydrate substrates. Injured cells reduced greater quantities of INT than healthy cells when NADH was used as a substrate. A comparison of metabolic end products suggested that injured cells also had considerable differences in carbon flow compared with healthy cells.

Synthesis and NMR spectra of 13C-labeled coenzyme A esters.

The synthesis of coenzyme A thioesters of 13C-labeled acetate, propionate, succinate, and methyl malonate is described. The average yields were 94%. The 13C-NMR spectra were determined to provide a reference for the resonance positions of these metabolites. The synthesis of coenzyme thioesters of small-molecular-weight acids labeled with 13C has not been described previously, nor have the resonance positions been previously reported.

Stabilizing effect of acetate salts and HCO-3 in digestors receiving high levels of glucose.

Anaerobic digestors were fed daily with dairy cattle manure (5% total solids) augmented with 0-20 mM glucose and were monitored daily for gas volume and composition and volatile acid content. Propionate accumulated in digestors that were fed glucose at initial digestor concentrations of 10 mM or more. Digestors that received 14-20 mM glucose failed, but identical digestors that received 20 mM glucose plus 10 mM acetate or HCO-3 did not fail. The sparing effect of HCO-3 was primarily buffering and the similar behavior of digestors that received acetate suggest that acetate metabolism perhaps provided additional HCO-3 for buffering. Analyses of H2 and volatile acid concentrations during a 6-8-h period following feeding in digestors fed glucose or glucose plus acetate showed that propionate and H2 accumulated simultaneously and that H2 concentrations were 3 microM or less. Monitoring 13C-labeled glucose metabolism via 13C nuclear magnetic resonance indicated that glucose was primarily converted to lactate and that the major product from lactate was propionate in both glucose and glucose plus acetate fermentations.

Application of C-nuclear magnetic resonance to the observation of metabolic interactions in anaerobic digestors.

The utilization and conversion of glucose to volatile acids were monitored in anaerobic digestors by C-nuclear magnetic resonance. Glucose was converted to lactate and acetate. Lactate was subsequently converted to propionate. The distribution of the labeled carbons in propionate suggested that minor amounts were produced via the randomizing pathway and that the major portion of propionate was derived from lactate.

Isolation and properties of a lectin from sainfoin (Onobrychis viciifolia, Scop.).

A glycoprotein capable of binding simple carbohydrates and causing hemagglutination has been isolated from seeds of the legume plant sainfoin (Onobrychis viciifolia, Scop. var Eski). The phytolectin was prepared by affinity chromatography of pH 7.0 sodium phosphate extracts on columns of Sepharose-4B containing covalently attached D-mannose. Molecular weight determinations showed the lectin to be a dimer consisting of 26 000 dalton, non-covalently associated monomers. Amino acid analyses indicated high amounts of aspartate, glutamate, threonine and serine which accounted for 41% of all amino acids. One residue of cysteine was present and methionine was totally absent. The lectin contained 2.6% (w/w) neutral carbohydrate and two residues of N-acetylglucosamine/monomer. Carbohydrate-binding specificity was directed toward D-mannose and D-glucose and their alpha-glycosidic derivatives. The purified protein agglutinated cat erythrocytes at 5 micrograms/ml. Antiserum to seed lectin showed a single common immunoprecipitation line in Ouchterlony double diffusion against both the seed and root antigen. Lectin isolated from sainfoin seedling roots showed molecular weight, amino acid and carbohydrate values similar to that of the seed lectin.

Methane production from cattle waste and delignified straw.

Methane production from added substrate per se was approximately twofold greater from delignified straw than that from untreated straw when fermented with cattle manure.

The structural subunit of glucose-6-phosphate dehydrogenase (baker's yeast).

The subunit molecular weight of glucose-6-phosphate dehydrogenase (G6PD) from baker's yeast has been evaluated. The subunit molecular weight value is shown to be 25,500 daltons by analytical ultracentrifugation, SDS-polyacrylamide gel electrophoresis, and the number of peptides produced by CNBr cleavage. The number of NADP binding sites was determined to be one per 25,500 dalton unit.