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Biomedical subjects

R E Hungate

Publications and source records attributed to R E Hungate.

At least 19 recordsLinked to original sources
PubMed1984

alpha-L-arabinofuranosidase from Ruminococcus albus 8: purification and possible role in hydrolysis of alfalfa cell wall.

An alpha-L- arabinofuranosidase has been purified from the extracellular broth of cultures of Ruminococcus albus 8. The purification procedure utilized gel filtration, (NH4)2SO4 precipitation, and isoelectric focusing. The purified enzyme appeared to be homogeneous when chromatographed on disc and analytical isoelectric focusing gels. The estimated molecular weight of the native protein was 305,000 to 310,000. Sodium dodecyl sulfate-gel electrophoresis analysis suggested that the native protein is a tetramer composed of 75,000-molecular-weight subunits. The enzyme appeared to have no metal cofactor requirement but was sensitive to several sulfhydryl reagents. The pH optimum with p-nitrophenyl-alpha-L-arabinofuranoside as the substrate was 6.9 and the Km was 1.3 mM. Several lines of evidence indicated that the enzyme is a glycoprotein. When assayed against alfalfa cell wall material, the enzyme hydrolyzed only small amounts of arabinose from the substrate. When assayed together with hemicellulolytic or pectinolytic enzymes against the same substrate, the arabinosidase significantly enhanced the hydrolytic action of the glycanases .

Ammonium Sulfate↗
PubMed1984

Muralytic Activities of Ruminococcus albus 8.

Ruminococcus albus 8 was cultured with isolated alfalfa cell walls as the carbon source. The culture broth was assayed for muralytic enzyme activities. The effect, with respect to the production of such muralytic enzymes, of growing the microorganism on different carbon sources was also investigated. Also, the rates of solubilization and utilization by R. albus of individual alfalfa cell wall sugars during a 96-h growth period were examined.

Journal Article↗
PubMed1984

Effect of 3-Phenylpropanoic Acid on Capsule and Cellulases of Ruminococcus albus 8.

The morphology and cellulases of Ruminococcus albus 8 were markedly affected by the inclusion of 3-phenylpropanoic acid (PPA) in a defined growth medium. PPA-grown bacteria produced substantial quantities of cell-bound cellulase, as well as a very high-molecular-weight extracellular enzyme and lesser amounts of two low-molecular-weight enzymes. PPA-deprived bacteria produced greater total amounts of cellulase, but all of it exists in soluble, low-molecular-weight forms. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that the availability of PPA did not affect the kinds of proteins produced, but the distribution of two major proteins between cells and supernatant was PPA dependent. These two proteins (85 and 102 kilodaltons) were primarily associated with the cells of PPA-grown bacteria but were found chiefly in the supernatants of PPA-deprived cultures. Examination of thin sections of PPA-grown R. albus 8 by transmission electron microscopy showed a lobed ruthenium red-staining capsule surrounding the cell wall, as well as small vesicular structures (diameter, 0.05 to 0.06 mum) which appeared to aggregate into larger spherical units (diameter, 0.2 to 0.3 mum). In contrast, thin sections of PPA-deprived cells were devoid of vesicles and showed little or no capsule surrounding the cells.

Journal Article↗
PubMed1983

Phenylacetic acid stimulation of cellulose digestion by Ruminococcus albus 8.

The rate of cellulose digestion by Ruminococcus albus 8 grown on a defined medium could be increased by adding a minimum of 6.6% (vol/vol) rumen fluid. Strain 8 was grown on half this concentration, and the culture medium before and after growth was analyzed by gas chromatography-mass spectrometry to determine which components of the rumen fluid were used. Phenylacetic acid was identified as the component needed to make the defined medium nutritionally equivalent to one supplemented with rumen fluid. [14C]phenylacetic acid fed to cultures of strain 8 was primarily incorporated into protein. Hydrolysis of protein samples and separation of the resulting amino acids showed that only phenylalanine was labeled. The results indicate that cellulose digestion by strain 8 was probably limited by phenylalanine biosynthesis in our previously reported medium. The data obtained on the utilization of other rumen fluid components, as well as on the production of metabolites, illustrate the potential usefulness of this method in formulating defined media to simulate those in nature.

Animals↗
PubMed1982

Phenylpropanoic Acid: Growth Factor for Ruminococcus albus.

Phenylpropanoic acid accounted for part of the stimulatory effect of rumen fluid on the rate of growth and of cellulose digestion by cultures of Ruminococcus albus strain 8 grown on a chemically defined medium. As little as 3 muM concentration gave maximum response.

Journal Article↗
PubMed1978

Bacterial ecology in the small intestine.

A modified intubation method allowed collection of samples of human small intestinal contents with no contamination from other intestinal sites and with no exposure to air. Use of the method has disclosed strains resembling Haemophilus as among the most abundant bacteria in the small intestine of some subjects. Stimulation by bile and rapid growth under conditions simulating the natural habitat suggest that it is well adapted to upper intestinal conditions.

Humans↗
PubMed1978

Reliable sampling method for analysis of the ecology of the human alimentary tract.

An intubation method has been developed that allows removal of a sample of human intestinal fluid within a short period of time, that avoids contamination, and that minimizes exposure of the sample to air. Preliminary results obtained with this method have shown that the stomach and duodenum are essentially sterile and that the bacterial population present in the remainder of the small intestine is similar to that described by previous workers except that Veillonella species were encountered frequently and Haemophilus species were also detected in the lower jejunum and ileum of some individuals.

Bacteria↗
PubMed1977

Hydrogen utilization by clostridia in sewage sludge.

A sporeformer morphologically different but physiologically similar to Clostridium aceticum Wieringa was isolated from sewage sludge. It used large amounts of H2 and CO2, converting them chiefly to acetic acid. Growth occurs anaerobically on yeast extract alone, but after the nutrients in yeast extract are used, growth continues at a reduced rate, supported by the conversion of the gases to acetate.

Acetates↗
PubMed1976

Desulfovibrio of the sheep rumen.

A sulfate-reducing bacterium has been isolated in pure culture from sheep rumen contents. Its properties agree in all respects tested with those ascribed to Desulfovibrio desulfuricans. The populations observed (about 10(8)/ml) are sufficient to account for published rates of ruminal sulfide production.

Animals↗
PubMed1976

Effect of alfalfa fiber substrate on culture counts of rumen bacteria.

A medium has been developed using alfalfa fiber as the sole substrate. It gave high culture counts (3 X 10(9) to 8 X 10(9)/ml) of rumen bacteria. When this medium was combined with the medium 98-5 of Bryant and Robinson, modified to contain 33% rumen fluid instead of 40% clarified rumen fluid, a higher count was obtained than with either medium alone.

Anaerobiosis↗
PubMed1974

Stomach fermentation in East African Colobus monkeys in their natural state.

The microbial fermentation in the stomachs of two monkeys, Colobus polykomos, collected in Kenya, was studied. The gas accumulated within the stomach contained H(2) but no CH(4). Volatile fatty acid concentrations were high, but accumulated acid prevented determination of the fermentation rate in untreated, incubated stomach contents. Upon addition of bicarbonate, a very rapid rate could be demonstrated. Some D- and L-lactate were in the stomach contents. Starchy seeds or fruits rather than leaves appeared to have been consumed. Microscopically, the most prominent microorganisms seen were large, very refringent cocci, possibly Sarcina ventriculi, and various smaller cocci and rods. The 28 cultured strains of bacteria included 14 Staphylococcus, 2 Streptococcus, 10 Propionibacterium, and 2 Peptostreptococcus. The culture count constituted 10 to 20% of the direct count. No protozoa or cellulolytic bacteria were found.

Animals↗
PubMed1973

Estimation of growth rate from the mitotic index.

The growth rate of a eukaryotic population dividing at a constant rate can be estimated from the equation, t(m)/g ln 2 = ln (1 + R), in which t(m) is the time required for mitosis, g is the generation time, and R is the fraction of cells undergoing mitosis. Values for t(m) and R can be determined by direct microscope examination of the population. The validity of the derived equation has been checked with an exponentially growing culture of a prokaryote, Escherichia coli, in which chloramphenicol was administered to inhibit protein synthesis. Cells having enough protein completed the division process whereas the rest of the population was inhibited. From the plot of the growth curve before and after administration of chloramphenicol, t(m) and R were estimated. The calculated and actual growth rates were almost identical.

Bacteria↗
PubMed1973

Factors affecting cellulolysis by Ruminococcus albus.

The factors influencing the digestion of pebble-milled cellulose by enzymes were studied by using several strains of Ruminococcus albus including a mutant characterized by a more eccentric location of its colony in the clearing produced by digestion of the cellulose in the thin layer lining the wall of a culture tube. Most of the cellulase is extracellular. As much as 65% of the cellulose could be digested by the cell-free enzymes provided the quantity of cellulose was small. Fresh enzyme was repeatedly administered or the digestion experiment was arranged in a dialysis bag through which digestion products could diffuse. Cellobiose and, to a lesser extent, glucose inhibited digestion. Pebble-milled filter paper, moist crystalline cellulose from cotton, and dry crystalline cellulose (Sigmacel) were digested, but in decreasing rapidity, respectively. Carboxymethylcellulose was digested more rapidly than pebble-milled cellulose but to approximately the same final extent as judged by Cu reduction values. Cell walls from alfalfa were digested. The enzyme preparation was active over the pH range 6.0 to 6.8 and showed most rapid cellulose digestion at 45 C. Part of the cellulolytic activity was irreversibly destroyed by exposure to oxygen. Much of the enzyme was absorbed on cellulose. The absorption and desorption characteristics, as well as the partial inhibition by oxygen, indicate that multiple enzymes are involved.

Adsorption↗