title: Sterol synergism in Paramecium tetraurelia.
abstract: Paramecium tetraurelia is a naturally occurring sterol auxotroph with an absolute nutritional requirement for one of a small group of structurally related phytosterols. We report here a quantitative study demonstrating that a low, otherwise sub-supportive, concentration (approximately 0.020-0.050 micrograms ml-1) of an essential phytosterol (stigmasterol) is adequate for growth of this ciliate, provided that a second, relatively non-specific sterol is available at a higher concentration (1.0 micrograms ml-1) to allow for membrane biosynthesis. This phenomenon, referred to as sterol synergism, has been observed in a broad taxonomic range of organisms, with the conclusion that small amounts of specific sterols are required to perform some previously unknown, vital metabolic or regulatory function. Paramecium promises to be an excellent model organism for the elucidation of essential sterol function.
authors.affiliation: Department of Biochemistry, University of Wisconsin-Madison, College of Agricultural and Life Sciences 53706.
authors.forename: B D
authors.initials: BD
authors.lastname: Whitaker
authors.forename: D L
authors.initials: DL
authors.lastname: Nelson
mesh_terms: D000818:Animals; D002784:Cholesterol / Q000031:analogs & derivatives / Q000378:metabolism; D003470:Culture Media; D004357:Drug Synergism; D004875:Ergosterol / Q000378:metabolism; D010247:Paramecium / Q000378:metabolism*; D010840:Phytosterols; D013261:Sterols / Q000378:metabolism*; D013265:Stigmasterol / Q000378:metabolism; D014315:Triterpenes / Q000378:metabolism
chemical_list: D003470:Culture Media; D010840:Phytosterols; D013261:Sterols; D014315:Triterpenes; C100046:tetrahymanol; C021273:campesterol; D002784:Cholesterol; D013265:Stigmasterol; D004875:Ergosterol