This is the first report on the mass cultivation of the mutant Tetrahymena thermophila SJ180; this strain has a temperature-sensitive food vacuole formation. The generation time, at both 28 degrees C (permissive temperature) and 39 degrees C (restrictive temperature) was determined in three commonly used complex media based, respectively, on proteose peptone (PPYS), skim milk (MYE), and hemoglobin hydrolysate (HB). The HB medium cost can be reduced by using a hemoglobin hydrolysate containing hemin residues (the decolorization step is thus avoided). The SJ180 strain grew in this medium only at 28 degrees C, at which it formed food vacuoles. The HE medium, which is more stable in its amino acid composition, was improved by glucose addition; this resulted in high cell densities. By omitting the major nitrogen source in complex media, we demonstrated that at both 28 degrees C and 39 degrees C, the SJ180 strain could be cultivated in media composed simply of yeast extract. Moreover, if salt solutions were added to the yeast extract, the results were similar to those in the three complex media (PPYS, MYE, and HB). Finally, we developed a very simple medium composed of yeast extract and glucose, which resulted in a longer stationary phase and cell populations twice as high as that in the reference media. Consequently, this medium is very advantageous, because it reduces the subculture numbers in cell collection.