Frozen Storage of Tritrichomonas foetus for 5.6 Years*

SYNOPSIS. Tritrichomonas foetus was cultivated in Diamond's medium without phosphates or agar; 10% glycerol was added to the medium and the protozoa were frozen slowly and stored at −28 or −95 C. About half of the trichomonads died within the first day at either temperature. Thereafter, they continued to die off slowly during storage at −28, and none remained alive at or after 1024 days. New cultures could not be initiated with them after 64 days. At −95, almost as many trichomonads were alive after 256 days as after 1 day. Thereafter, however, they decreased in numbers, but 11% were still alive after 2048 days (5.6 years). The survivors appeared in good condition, and new cultures were readily initiated with them.