The rate of uptake and metabolism of starch grains and cellulose particles by Entodinium species, Eudiplodinium maggii, some other entodiniomorphid protozoa and natural protozoal populations taken from the ovine rumen.

Abstract

The rates of engulfment and breakdown of starch grains and cellulose particles and of the rate of synthesis of amylopectin from cellulose by individual species of entodiniomorphid protozoa (grown in vivo and in vitro) and incubated anaerobically in vitro were studied. Rates of starch uptake varied from 2.3 to 770 micrograms/mg protozoal protein/min; the lowest was found with Diploplastron affine and the highest with Entodinium spp. on initial incubation with starch grains. The rate of starch breakdown varied from 0.49 to 8.6 micrograms/mg protein/min; the rate was dependent on the initial starch concentration inside the protozoa. Eudiplodinium maggii engulfed cellulose particles more rapidly (2-7 times) than rice starch grains and digested the cellulose at rates of 10 to 16.5 micrograms/mg protein/min. In a mixture of starch grains and cellulose particles, it engulfed the latter at 1.35 to 25 times the rate of the former. Eudiplodinium maggii and Epidinium caudatum, but not Entodinium spp. or Dip. affine, synthesized an amylopectin-like material from cellulose at rates of 0.4 to 4.75 micrograms/mg protein/min. If these reactions occur in the rumen in vivo, up to 9 g of amylopectin could be synthesized from cellulose each day by the entodiniomorphid protozoa.