Glycoside hydrolases of rumen bacteria and protozoa

Colony counts which approximated those in a habitat-simulating, rumen fluid-agar medium (RFM) were obtained in medium 10, a medium identical to the RFM except for the replacement of rumen fluid with 1.5 x 10(-6)m hemin, 0.2% Trypticase, 0.05% yeast extract, and a 6.6 x 10(-2)m volatile fatty acid mixture qualitatively and quantitatively similar to that in rumen fluid. Single deletion of Trypticase, yeast extract, or the volatile fatty acid mixture from medium 10 significantly reduced colony counts. Colony counts were also reduced when medium 10 was modified to contain higher concentrations of Trypticase or volatile fatty acids. Significant differences were found between colony counts obtained from diluted rumen contents of animals fed a cracked corn-urea diet, and the colony counts obtained from animals fed either a cracked corn-soyean oil meal or an alfalfa hay-grain diet. Qualitative differences were found between the predominant bacterial strains isolated from rumen contents of animals fed cracked corn diets and strains isolated from animals fed alfalfa hay-grain. Regardless of differences in the predominant flora associated with diet, medium 10 and the RFM supported growth of similar bacterial populations. The results show that medium 10 is suitable for enumeration and isolation of many predominant rumen bacteria.

This paper reports for the first time the presence in the anaerobic rumen ciliate Dasytricha ruminantium (Schuberg) of microbody-like organelles, about 0.5 micrometer diameter, with a granular matrix and an equilibrium density of approx. 1.18 g/ml. These organelles can be isolated in a fraction sedimented at 10(5) g-min that contains 67% of the total pyruvate synthase (EC 1.2.7.1), 66% of the hydrogenase (EC 1.18.3.1) and 20% of the lactate dehydrogenase (EC 1.1.1.27). Thus in several respects this fraction is enzymically similar to those containing hydrogenosomes in some other parasitic anaerobic protozoa (the trichomonads). However, in contrast with the hydrogenosomes of trichomonads, the oxygen-tolerant enzyme malate dehydrogenase (decarboxylating) (EC 1.1.1.40) is not particulate, but occurs only in the cytosol. These results enable the proposal of a scheme for the pathway of product formation (acetate, lactate, CO2 and H2) from carbohydrates.