The Effect of Glycerol and Related Compounds on Survival of Tritrichomonas foetus at Freezing Temperatures*

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Abstract
SUMMARY. The addition of 1.0–1.1 M (9–10%) glycerol to CPLM medium of Johnson and Trussell permits Tritrichomonas foetus to survive when frozen slowly to ‐20d̀ or ‐76d̀C. and stored at either temperature. After freezing to ‐76d̀C. at the rate of 1d̀C. per minute, 38% of the protozoa were alive after 1 day, and some survived more than 128 days. After freezing to ‐20d̀C. in 1–2 hours, 63% of the protozoa were alive after 1 day, 46% after 8 days, and some survived 32 to more than 128 days in different experiments. After freezing to ‐20d̀C. in about 7 hours, 68% were alive after 1 day, 36% after 8 days, and some survived 16 to more than 64 days in different experiments. A concentration of 0.55 M (5%) glycerol is about as effective as 1.1 M, but 0.14 and 0.28 M are much less effective. If the protozoa are snap‐frozen to ‐76d̀C., glycerol does not protect them, nor do they survive slow freezing without glycerol. In CPLM medium containing 1.0 M ethylene glycol, 72% of the protozoa were alive 1 day after having been frozen to ‐20d̀C. in about 7 hours, 29% were alive after 8 days, and some survived from 16 to more than 32 days in different experiments. The above figures are averages. In parallel tests at a concentration of 1.0 M in CPLM medium following slow freezing to ‐20d̀C. and storage at that temperature for 1 day, ethylene glycol was 80–90% as effective as glycerol; 1,2,3,4‐butanetetrol was 67% as effective; 1,2‐propanediol was 57% as effective; 2,3‐butanediol, 14%; mannose, 6%; and mannitol, 1%. Glycerol monoacetate and polyvinyl alcohol were inactive; and 2,3‐dimercaptopropanol was toxic.