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Biomedical subjects

R E Hungate

Publications and source records attributed to R E Hungate.

At least 37 records · Page 2Linked to original sources
PubMed1971

Parameters of rumen fermentation in a continuously fed sheep: evidence of a microbial rumination pool.

The feed and feces of a continuously fed sheep were analyzed for carbon, hydrogen, and nitrogen, with oxygen as the remainder. The daily feed-feces weight difference was used as the reactant in an equation representing the rumen fermentation. The measured products were the daily production of volatile fatty acids (VFA), CH(4), CO(2), and ammonia. The carbon unaccounted for was assumed to be in the microbial cell material produced in the rumen and absorbed before reaching the feces. The ratio of C to H, O, and N in bacteria was used to represent the elemental composition of the microbes formed in the rumen fermentation, completing the following equation:C(20.03)H(36.99)O(17.406)N(1.345) + 5.65 H(2)O --> C(12)H(24)O(10.1) + 0.83 CH(4) VFA + 2.76 CO(2) + 0.50 NH(3) + C(4.44)H(8.88)O(2.35)N(0.785) microbial cells absorbed With C arbitrarily balanced and O balanced by appropriate addition of water, any error is reflected in the H. The H recovery was 98.5%. The turnover rate constant for rumen liquid equilibrating with polyethylene glycol (PEG) was 2.27 per day. Direct counts and volume measurements of the individual types of bacteria and protozoa in the rumen were used to calculate the total microbial cell volume in the rumen, not equilibrating with it. The dry matter in the rumen (582 g) and the nitrogen content (12.05) of the microbes in the rumen were estimated, the latter constituting 85% of the measured N in the rumen. Calculations for rumen dry matter and nitrogen turning over at the PEG rate introduce big discrepancies with other parameters; a rumination pool must be postulated. Its size and composition are estimated. Arguments are presented to support the view that dry matter and some of the microbes, chiefly the protozoa, do not leave the rumen at the PEG rate. One experiment with the same sheep fed twice daily showed significantly less production of microbial cells than did the continuous (each 2 hr) feeding. Analysis of the microbial cell yield suggests that, on the basis of 11 mg of cells per adenosine triphosphate molecule, a maximum of six adenosine triphosphate molecules could have been formed from each molecule of hexose fermented.

Ammonia↗
PubMed1970

Formate as an intermediate in the bovine rumen fermentation.

An average of 11 (range, 2 to 47) mumoles of formate per g per hr was produced and used in whole bovine rumen contents incubated in vitro, as calculated from the product of the specific turnover rate constant, k, times the concentration of intercellular formate. The latter varied between 5 and 26 (average, 12) nmoles/g. The concentration of formate in the total rumen contents was as much as 1,000 times greater, presumably owing to formate within the microbial cells. The concentration of formate in rumen contents minus most of the plant solids was varied, and from the rates of methanogenesis the Michaelis constant, K(m), for formate conversion to CH(4) was estimated at 30 nmoles/g. Also, the dissolved H(2) was measured in relation to methane production, and a K(m) of 1 nmole/g was obtained. A pure culture of Methanobacterium ruminantium showed a K(m) of 1 nmole of H(2)/g, but the K(m) for formate was much higher than the 30 nmoles for the rumen contents. It is concluded that nonmethanogenic microbes metabolize intercellular formate in the rumen. CO(2) and H(2) are the principal substrates for rumen methanogenesis. Eighteen per cent of the rumen methane is derived from formate, as calculated from the intercellular concentration of hydrogen and formate in the rumen, the Michaelis constants for conversion of these substrates by rumen liquid, and the relative capacities of whole rumen contents to ferment these substrates.

Animals↗
PubMed1969

Methanogenic fermentation of benzoate.

A methanogenic enrichment culture decomposed small concentrations of (14)C-benzoate to (14)C(4) and (14)CO(2) under stringently anaerobic conditions with or without preceding exposure to benzoate.

Benzoates↗
PubMed1968

Factors influencing agnotobiotic cultures of the rumen ciliate, Entodinium simplex.

The nutrition of Entodinium simplex was studied, with foliage of bluegrass (Poa pratense), perennial ryegrass (Lolium perenne), and grains of wheat (Triticum vulgare) as substrates in agnotobiotic cultures. Entodinium grew poorly when the substrates were autoclaved; better growth was obtained when the substrates were sterilized with ethylene oxide vapor. The concentration of ethylene oxide and the amount of moisture influenced the sterility and nutritional adequacy of the treated substrate. Autolysates and hydrolysates of mixed rumen protozoa stimulated growth. Protozoal extracts did not replace factors destroyed by autoclaving. Clarified rumen fluid assisted the cultivation of entodinia from small inocula but was detrimental to established cultures. Success of cultures was influenced by the medium used to grow the inoculum as well as by the medium inoculated. The results indicated that the composition of the bacterial population influences the growth of E. simplex.

Animals↗
PubMed1968

Characterization of Methanobacterium mobilis, sp. n., isolated from the bovine rumen.

A methanogenic bacterium, present in bovine rumen contents at concentrations of approximately 2 x 10(8) cells per ml, has been isolated in pure culture. The organism is a strictly anaerobic, weakly motile, nonsporeforming, gram-negative rod (0.7 mu x 1.5 to 2.0 mu) with rounded ends. There is a single polar flagellum. The organism grows at temperatures between 30 and 45 C, with an optimum at 40 C, and at pH values between 5.9 and 7.7, with optimal growth between pH 6.1 and 6.9. Of the 17 substrates tested, only formate and H(2) plus CO(2) supported growth. An unidentified, heat-stable factor(s) was required by the organism. The factor, which was not one of the common ones, was present in rumen fluid, mixed rumen bacteria, and yeast extract. On the basis of colony morphology, Gram reaction, and motility, the organism is classified as a new species of methanogenic bacterium, and the name Methanobacterium mobilis sp. n. is proposed.

Animals↗
PubMed1967

Amino acid concentrations in rumen fluid.

Methods using dialysis or ultrafiltration are described for the collection of extracellular fluid in rumen contents for analysis of amino acids. Marked differences in the concentration of aspartic acid, glutamic acid, and alanine were found in samples of either diffusate or ultrafiltrate and in clarified acidified rumen liquor. Concentrations are given for aspartic acid, glutamic acid, alanine, glycine, gamma-aminobutyric acid, valine, delta-aminovaleric acid, and leucine.

Amino Acids↗
PubMed1967

Metabolism of glycine by rumen microorganisms.

Rumen microorganisms rapidly metabolized glycine at rates varying from 0.014 to 0.241 mumole of glycine per ml per min. The main metabolic products were carbon dioxide, acetic acid, and ammonia; little glycine was incorporated into bacterial protein. Use of carboxyl or methylene-labeled glycine showed that the carbon dioxide came mainly from the carboxyl of glycine, whereas both carbons of acetic acid were derived partly from the methylene carbon of glycine and partly from carbon dioxide. The ratio of carbon-14 to nitrogen-15 in glycine isolated from the protein of rumen bacteria incubated in the presence of N(15)- and C(14)-labeled glycine indicated that most of the extracellular glycine incorporated into protein was incorporated without intervening deamination.

Animals↗
PubMed1966

Method for measuring diaminopimelic acid in total rumen contents and its application to the estimation of bacterial growth.

Diaminopimelic acid (DAP) was measured in rumen samples for which growth rate had previously been estimated from changes in fermentation capacity. The growth measurements by the two methods agreed within the experimental error. Agreement between the rate of bacterial growth (DAP) and total microbial growth (fermentation capacity) suggests that the protozoa also grow at about this rate.

Animal Feed↗
PubMed1966

Culture of the rumen holotrich ciliate Dasytricha ruminantium schuberg.

The successful cultivation of the anaerobic ciliate Dasytricha ruminantium is described. The cultures were established in a salts medium containing 30% clarified rumen fluid. Sucrose and extract of rumen holotrich protozoa were fed once daily for 2 to 4 hr, and Dasytricha was then transferred to medium free from these nutrients. Rumen fluid was essential. Omission of protozoal extract resulted in gradual death of the ciliates. Bovine serum satisfactorily substituted for the protozoal extract, but various rumen bacteria, extract of rumen bacteria, and extracts of plant materials could not. There was a positive correlation between formation of methane in the cultures and growth of the ciliates. It is possible that methane bacteria were ingested, but it is not excluded that survival of both dasytrichs and the methanogenic bacteria depended on a low redox potential of the medium.

Animals↗