Ref ID : 4108
Walter Guyer and Konrad Bloch; The Sterol Requirement of Tetrahymena setosa HZ-1. J.Protozool. 30(4):625-629, 1983
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The growth rate of Tetrahymena setosa cells is stimulated significantly by as little as 0.1 µg and optimally by about 1 µg of ergosterol per ml of medium. Cell yields in the stationary phase are, however, not perceptibly affected by increasing sterol concentrations. Ergosterol, in concentrations that stimulate growth optimally, does not cause a reduction of tetrahymanol synthesis. The latter process is impaired only at much higher ergosterol concentrations. Epicholesterol and coprostanol inhibit ergosterol-stimulated growth competitively. It is concluded that the trace amounts of sterol needed by T. setosa do not serve to replace tetrahymanol but function in some other manner, probably unrelated to the control of membrane fluidity. This conclusion supports the views advanced earlier by Holz, Erwin, Wagner & Rosenbaum.