The uptake and utilization of Entodinium caudatum, bacteria, free amino acids and glucose by the rumen ciliate Entodinium bursa

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Abstract
Washed suspensions of E. bursa were incubated anaerobically with E. caudatum, 10 spp. of bacteria and a yeast [Bacillus megaterium, Butyrivibrio fibrisolvens, Escherichia coli, Eubacterium cellulosolvens, Klebsiella aerogenes, Megasphaera elsdenii, Proteus mirabilis, Ruminococcus flavefaciens, Selenomonas ruminantium, Streptococcus bovis and Torulopsis glabrata]. The rate of uptake and digestion of these microorganisms was investigated. Protozoa grown in vivo did not engulf Proteus mirabilis or Klebsiella aerogenes but rapidly took up Bacillus megaterium, Selenomonas ruminantium, Torulopsis glabrata and Streptococcus bovis, although only the last was digested with release of soluble material into the medium. Protozoa grown in vitro engulfed each of the bacteria tested, taking up Megasphaera elsdenii and P. mirabilis most rapidly. Individual bacterial species and mixed rumen bacteria were engulfed more rapidly (up to 20 times) by protozoa grown in vivo than those grown in vitro, although the latter digested over 80% of the B. megaterium, Escherichia coli and P. mirabilis taken up. Labeled Entodinium caudatum was extensively digested after engulfment by E. bursa. Some of the digestion products were released into the medium but individual amino acids were transferred as such from E. caudatum protein to E. bursa protein. Engulfed bacteria and polysaccharide granules were transferred intact from one protozoon to the other. Free amino acids were also taken up intact from the medium into protozoal protein but there was little biosynthesis of amino acids from glucose. When available for engulfment E. caudatum was quantitatively a much more valuable source of amino acids for protein synthesis by E. bursa than free amino acids or bacteria.