Chemical Composition of Mycoplasma Cells and Membranes

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Abstract
The chemical composition of whole organisms and cell membranes of eight saprophytic and parasitic Mycoplasma strains was studied. Cell membranes of M. laidlawii and M. bovigenitalium were prepared by osmotic shock. The membranes comprised about 35% of the dry weight of the organisms. Generally the solid residue of the mycoplasmas contained 54-62% protein, 12-20% lipid, 3-8% carbohydrate, 8-17% ribonucleic-acid (RNA) and 4-7% deoxyribonucleic-acid (DNA). Cell membranes contained 47-60% protein, 35-37% lipid, 4-7% carbohydrate and small amounts of RNA and DNA which could not be washed away with de-ionized water. The saprophytic M. laidlawii contained only one-fourth to one-third of the total cholesterol found in the lipid of the parasitic strains. No cholesterol was detected in M. laidlawii grown in cholesterol-free media. Acetone-insoluble lipids formed the major part of the lipid in the saprophytic strains, and the minor part in the lipid of the parasitic strains. The carotenoid pigments of M. laidlawii were retained in the cell membrane preparations.