%0 Journal Article %A Conner, R. L. %A Van Wagtendonk, W. J. %T Steroid Requirements of Paramecium aurelia %D 1955 %J Microbiology, %V 12 %N 1 %P 31-36 %@ 1465-2080 %R https://doi.org/10.1099/00221287-12-1-31 %I Microbiology Society, %X Summary: Paramecium aurelia, var. 4, stock 51·7 (s) requires a steroid as a growth factor; β- and γ-sitosterol, fucosterol, brassicasterol, stigmastcrol and Δ4,22-stigmastadienone are active in supporting its growth. Esterification of the 3-hydroxyl group decreases the activity. The presence of more than one double bond in the ring system inactivates the molecule, as do the more drastic changes of the side chain, as found in diosgenin, digoxigenin, progesterone, estrone and methyl cholate. Oxidation of the ring system destroys activity. The specificity of these requirements suggests that the steroid functions as an essential metabolite for this organism. %U https://www.microbiologyresearch.org/content/journal/micro/10.1099/00221287-12-1-31