Tritrichomonas foetus: Partly defined cultivation medium for study of the purine and pyrimidine metabolism

A partly defined medium was successfully designed for the cultivation of Tritrichomonas foetus, an anaerobic protozoan parasite of cattle. The medium consists of hypoxanthine, uracil, and thymidine as the sole precursors of nucleotides in T. foetus. Elimination of any one of the three precursors from the medium led to cessation of T. foetus growth. The information provided by this medium verifies our previous observations that T. foetus is incapable of de novo purine and pyrimidine synthesis, that hypoxanthine can be converted to AMP and GMP, that uracil is incorporated into all pyrimidine ribonucleotides including UDP-glucose—the precursor of glycogen synthesis, and that thymidine is the only precursor of TMP. The omission of folate from the medium, without affecting growth of T. foetus, also supports our previous finding that the parasite does not have functioning dihydrofolate reductase or thymidylate synthetase. The successful plating of T. foetus on agar plates incorporating the partly defined medium with near 100% plating efficiency makes it possible to isolate T. foetus mutants for further studies of purine and pyrimidine metabolism in this parasite.