Rothblat, George H. (University of Pennsylvania, Philadelphia), and Paul F. Smith. Nonsaponifiable lipids of representative pleuropneumonia-like organisms. J. Bacteriol. 82:479–491. 1961.—The fate of cholesterol and the nature of carotenoid pigments in various strains of pleuropneumonia-like organisms have been determined by characterization of their nonsaponifiable lipids. All of the cholesterol removed from the medium by a nonfermentative sterol-requiring strain remains unchanged except for a portion of it being esterified. A fermentative sterol-requiring strain of avian origin converts part of the cholesterol to cholesteryl-β-d-glucoside, the amount in the glucoside form being governed by the amount of glucose supplied in the growth medium. This cholesteryl-β-d-glucoside was found to be formed by a fermentative, nonsterol-requiring strain only when supplied exogenous cholesterol. No cholesterol or its derivatives were found in nonsterol-requiring strains when grown in the absence of cholesterol. Three carotenoid pigments were isolated from nonsterol-requiring strains. The most nonpolar pigment was identified as neurosporene. The second pigment appearing in chromatographic column eluates appears to be a hydroxylated neurosporene, based on its polarity and absorption spectrum. The most polar pigment was found to contain reducing sugar following acid hydrolysis and appears to be a carotenoid-glucose complex. When the nonsterol-requiring strains are grown in the presence of cholesterol, cholesterol partially supplants the role of carotenoids and decreases the amount of carotenoids synthesized. The role of steroids and carotenoids in these organisms is discussed.

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