LIPID REQUIREMENTS FOR THE GROWTH OF PLEUROPNEUMONIALIKE ORGANISMS

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Abstract
A study of quantitative growth responses of pleuropneumonialike organisms to various lipids showed that cholesterol at a level of 0.01 mg/ml satisfactorily supplies the sterol requirement. Certain fatty acid esters of cholesterol and sterols with only minor modifications from cholesterol in the side chain and ring structure permit growth. The 3-[beta]-hydroxyl group, the ring structure and the intact side chain are required for growth. Biosynthetic precursors of cholesterol are inactive. Several sterols were inhibitory to growth. The phospholipid requirement can be met with lecithin and partially with sodium cholate but not with cephalin or the component parts of a lecithin. A ratio of cholesterol: phospholipid of 2 or greater permits optimal growth, while a ratio less than 2 results in inhibition. Acetate was demonstrated to be a stimulatory growth factor, which could be replaced with catalytic amounts of acetate plus substrate amounts of other short chained fatty acids.