Effect of ciliate protozoa on the activity of polysaccharide‐degrading enzymes and fibre breakdown in the rumen ecosystem

Abstract

The effect of ciliate protozoa on the activity of polysaccharide‐degrading enzymes in microbial populations from the digesta solids and liquor fractions of rumen contents was examined after the refaunation of ciliate‐free sheep with an A‐type rumen protozoal population. Although the culturable rumen bacterial population was reduced after refaunation the number of fibrolytic micro‐organisms detected was higher; the xylanolytic bacterial population and numbers of fungal zoospores were increased after refaunation. The proportion of propionic acid was lower in the refaunated animals, whereas the concentration of ammonia and the acidic metabolites acetate, butyrate and valerate were all increased. The range of enzyme activities present in the digesta subpopulations were the same in defaunated and refaunated animals. The activities of the polysaccharide‐degrading enzymes, however, were increased in the microbial populations associated with the digesta solids after refaunation, and at 16 h after feeding the activities were 4–8 times (β‐d‐xylosidase 20 times) higher than the levels detected in the adherent population from defaunated sheep. The protozoa, either directly through their own enzymes or indirectly as a consequence of their effects on the population size and activity of the other fibrolytic micro‐organisms present, have an important role in determining the level of activity of polysaccharide‐degrading enzymes in the rumen ecosystem. Although the extent of ryegrass (Lolium perenne) hay digestion was similar after 24 h in the absence or presence of protozoa, the initial ruminal degradation was higher in refaunated sheep.

Relative Contributions of Bacteria, Protozoa, and Fungi to In Vitro Degradation of Orchard Grass Cell Walls and Their Interactions

“…Coleman (8, 9, 10), Newbold et al (26), and Williams and Withers (41) suggested that as much as 62% of the cellulolytic activity associated with plant material in the rumen may be protozoal in origin. However, in our experiments, the protozoal fraction alone did not progressively degrade cell wall material.…”

Analysis of Community Structure and Species Richness of Protozoa-Enriched Rumen Metagenome from Indian Surti by Shotgun Sequencing

“…Genes coding for central carbohydrate metabolism and onecarbohydrate metabolism were most dominant within this category and it is unsurprising that protozoa play a critical role in all the subsystems of carbohydrate metabolism. Previous reports have suggested that about 62% of the total cellulolytic activity associated with plant materials may be attributed to protozoa [45][46][47] . A noteworthy feature of the functional potential of rumen protozoa was the abundance of genes for iron acquisition and metabolism, suggesting a high potential of protozoa to compete for iron with other members of microbial community.…”

The ability of the rumen ciliate, <i>Diploplastron affine</i>, to digest polysaccharides from fungal and bacterial cell walls

“…Rumen ciliates engulf large amounts of fungal zoospores and bacteria (Williams and Coleman, 1992). The cell walls of these organisms are rich in chitin and murein, respectively.…”