RUMEN CILIATES - THEIR METABOLISM AND RELATIONSHIPS WITH BACTERIA AND THEIR HOSTS

To explore the ruminal ecosystem, this paper is an attempt to illustrate the biochemistry and the metabolism of rumen protozoa. Different culture techniques (gnotobiotic, axenic, continuous culture) of ciliate protozoa are reviewed. The ability of ciliates to invade plant tissues, their association and the degradation of plant cell constituents (cellulose, hemicellulose, pectin, glycolipids), and the use of starch and soluble sugars for polysaccharide storage are determined. The interrelationships between ciliate protozoa and bacteria are discussed. These include the enzymic degradation of the engulfed plant particles, the bacterial nitrogen (amino acids, nucleic acids), and vitamins and trace element supplies as nutrient sources for protozoa. The composition of the rumen ciliate population, controlled by phylogenetic factors, geographical distribution, feeding habits and physiological status of the host, by competition between microorganisms and by the diet (nature of the diet, number of meals), is related. The transmission and establishment of the microfauna and its contribution to the microbial nitrogen available for the host are discussed. © 1990.