Symposium on Microbiology of the Rumen.

The importance of microorganisms to the mixed activities could be obtained. For this ruminant has interested an increasing number of reason, and because the pure culture approach nutritionists, particularly those in departments is time consuming, methods for studying the of animal science. In view of this interest of natural mixture have been developed. The inagricultural workers, it is surprising to find relafluence of various factors can be tested, the tively few rumen microbiologists. Formal disassumption being that their effects in vitro and cussions on this subject have been held in Engin the rumen will be similar. land and France, but the Rumen Microbiology The first four papers of the symposium disSymposium at the Fifty-fifth General Meeting cussed results obtained by the analytical apof the Society of American Bacteriologists was proach. R. E. Hungate reviewed the types of the first in the United States. It was arranged cellulolytic bacteria characteristic of the rumen: to present and compare different points of view Bacteroides succinogenes, Ruminococcus flavefarather than to summarize current knowledge. ciens, colorless cellulolytic cocci, butyric acidA more extensive meeting, including participaproducing nonsporeforming rods, and sporetion by microbiologists from many countries, formers which produce butyric acid. A need for would be necessary for an adequate treatment of study of fermentation patterns within the genus all phases of the subject. Bacteroides was discussed. The unnamed bacteria The methods discussed fell into two cateneed taxonomic study leading to assignment of gories, analyses of the activities of individual binomials. The gram reaction and morphology of types, and study of the integrated activities of the colorless cocci would place them in the genus part or all of the rumen biota. The analytical Veillonella, but their fermentation pattern differs approach assumes that for a complete underfrom the type species in that no propionic acid is standing of the rumen fermentation the informed. M. Rogosa suggested that a new genus dividual components must be isolated and should be created for these colorless cocci. studied under controlled and reproducible condiThe fermentation products of the cellulolytic tions. This involves classical pure culture techbacteria, as found in the pure cultures, include niques as well as analyses of the culture H2, C02, formic, acetic, butyric, lactic, and requirements and fermentation characteristics of succinic acids, and ethanol. The acetic and each species. Not only physiological and biobutyric acids and carbon dioxide are final chemical problems are encountered, but also products also in the rumen. Conversion of lower knotty questions in morphology, taxonomy, and fatty acids into higher ones has been found in ecology, each of which may require extended pure cultures and may occur also in the rumen. study. If appropriate culture conditions are emLactic acid is converted via two fermentations, ployed, much of the knowledge about each pure one a propionic type with also acetic acid and culture probably applies to that organism also CO2 formed, and one a butyric type with also in the rumen mixture, but even if abundant inacetic acid, formic acid, C02, and H2. Formic formation on pure cultures of all rumen species acid is decomposed to H2 and C02. Succinic acid were available, it is doubtful that from the pure is decarboxylated to propionic acid. Hydrogen is culture data alone an accurate picture of the used for the reduction of C02 to CH4. Ethanol is not a final product in the rumen; it presumably 1 This symposium consisted of six formal papers is formed, but its further conversions have not and a following discussion. Lack of time prevented been determined. the participants from preparing any mutually been applied acceptable formulation of principles of rumen microbiology. This summary by the convenor, to the rumen protozoa, though pure cultures have R. E. Hungate, is an attempt to indicate the chief not been obtained. The role of the protozoa in accomplishments and viewpoints expressed. the rumen was reviewed by J. Gutierrez. Pro2 Convenor. cedures for mechanically separating the protozoa