The Metabolism of Bacterial Nucleic Acid and of Free Components of Nucleic Acid by the Rumen Ciliate Entodinium caudatum

SUMMARY: Washed suspensions of Entodinium caudatum grown in vitro and incubated anaerobically in the presence of penicillin and neomycin for up to 6 hr incorporated 14C-adenine, guanine and uracil into the cell. The 14C was distributed between the cell pool of the protozoa and the nucleic acid. 14C-Thymine was incorporated only into the pool. There was some interconversion of the nucleic acid bases: guanine was converted to adenine and uracil to cytosine. Adenine and guanine were broken down in the medium to a mixture of hypoxanthine and xanthine, and uracil and thymine were reduced to their dihydro-derivatives. E. caudatum suspensions also incorporated purine and pyrimidine bases, ribose and phosphate from bacterial nucleic acid into protozoal nucleic acid and evidence was obtained that the former was degraded as far as individual nucleotides before incorporation into the latter. No evidence was obtained for the synthesis of protozoal ribose from other carbohydrates.