Temperature-Enhanced Osmotic Growth Requirement of Crithidia*†

SYNOPSIS. An osmotic growth requirement for the trypanosomatid Crithidia fasciculata became conspicuous at 32 C. Osmo-supportive compounds were surveyed at 28 vs. 33 C, in “low-osmotic” defined medium. Effective osmotic support was provided by many compounds, e.g., glycerophosphate, sorbitol, mannitol, glycerol, Na isethionate, glycine, arginine, KCl, NaCl, NH₄Cl, and K₂SO₄. The nonspecificity of the requirement was thus evident, but inactivity of the presumably poorly adsorbable pentaerythritol indicated that osmotic pressure was a likely but insufficient condition for satisfying the temperature-enhanced growth requirement most clearly expressed as a need for osmotic support. Fortification of the medium with a combination of glycerophosphate, glycine, glycerol, and Tween 80 permitted good growth at 35 C. Possible relations between the temperature-enhanced osmotic requirement cell membrane damage, and morphological phases of Trypanosoma and Leishmania are discussed.