The metabolism of starch, glucose, amino acids, purines, pyrimidines and bacteria by the rumen ciliate Polyplastron multivesiculatum.

The large rumen ciliate protozoon Polyplastron multivesiculatum grown in vitro engulfed a wide range of bacteria (from a population density of 10(9) bacteria ml(-1)) at a rate of 1500 to 137000 bacteria h(-1) protozoon(-1). No evidence was found for the preferential engulfment of bacteria of rumen origin. Except for Proteus mirabilis none of the bacteria were digested with the liberation of soluble materials into the medium. Glucose and amino acids were taken up rapidly by P. multivesiculatum compared with the rate of uptake by Entodinium caudatam. Glucose was incorporated into protozoal polysaccharide and into bacteria associated with the protozoa and was used for the synthesis of a wide range of amino acids. Evidence showed that bacteria and free amino acids at the concentrations found in the rumen could supply the protein requirements of the protozoa for division at least once each day.