ABSTRACT
Lipid metabolism in trichomonads has been little studied, but is clearly defective, the organisms being viewed as fatty acid and sterol auxotrophs. These beliefs date from the nutritional experiments of Cailleau (1936, 1938) who demonstrated that Tritrichomonas foetus required cholesterol when cultured in a solvent-extracted peptone and serum medium. This association of the cholesterol requirement with serum then led to determined efforts by Shorb and Lund (1959) to culture a variety of trichomonads in chemically defined media, by substituting lipids for serum. The fatty acids (palmitic and oleic), cholesterol, tocopherol and a solvent-extracted tryptic digest of casein were effective serum substitutes for the growth of Trichomonas gallinae (Shorb and Lund, 1959). It was found that C14 to C18 saturated fatty acids were nutritionally active when coupled with oleic acid, and C18 to C22 unsaturated fatty acids were active when coupled with palmitic acid. Purified cholesterol, cholestanol and zymosterol were nutritionally active (Lund and Shorb, 1962). In 1981, Linstead succeeded in growing Trichomonas vaginalis in a basal medium patterned after those used for vertebrate tissue cultures. Good growth was obtained when the medium was supplemented with palmitic, stearic and oleic acid (supplied as such or in a synthetic triacylglycerol) and cholesterol all complexed to bovine serum albumin. Peterson and Alderete (1984) presented evidence that the lipid requirements of T. vaginalis can be met by receptor-mediated endocytosis of human lipoproteins, supplied in Diamond’s medium (1968) or in a semi-defined medium containing trypticase, vitamins, nucleic acid precursors and maltose.
