The Sterol Content of Some Protozoa

SYNOPSIS. The sterols of a number of protozoa grown in axenic culture have been examined. Ergosterol is present in Polytoma uvella, Astasia ocellata, Haematococcus pluvialis, Crithidia oncopelti, Prototheca zopfii, Chilomonas paramoecium and Trypanosoma mega , all grown on sterol-free media. Ergosterol is also present in the culture form of Trypanosoma rhodesiense and occurs together with cholesterol and an unidentified sterol in Peranema trichophorum grown in the presence of cholesterol. P. uvella, A. ocellata, H. pluvialis and C. oncopelti also contain a sterol which is either spinasterol or its isomer chondrillasterol. The main sterol of Ochromonas malhamensis is probably poriferasterol, which is also present in C. paramoecium. Cholesterol, probably from the environment, is the only sterol in the blood form of T. rhodesiense. Tetrahymena pyriformis and Hartmannella rhysodes do not synthesize sterols.