Some studies on the fatty acid composition of total lipids and phosphatidylglycerol from Acholeplasma laidlawii B and their relation to the premeability of intact cells of this organism

1. 1. Acholeplasma laidlawii B (previously denoted as Mycoplasma laidlawii B) was grown in the presence of equimolar mixtures of palmitic or stearic acid and the following unsaturated fatty acids: elaidic, oleic, linoleic, or arachidonic acid. 2. 2. Significant differences were observed in the fatty acid composition of total lipids and phosphatidylglycerol after growth in the presence of the various mixtures of fatty acids. Decreasing amounts of unsaturated fatty acids were incorporated in the following order: elaidic > oleic > linoleic > linolenic > arachidonic acid. This decrease was found to be counterbalanced by an increased uptake of saturated fatty acids. 3. 3. The permeability of intact cells of Acholeplasma, after growth on the indicated mixtures of fatty acids was found to be maintained within certain limits. These observations indicate that A. laidlawii B is equipped with a mechanism to control the fluidity of its membrane lipids and, hence, the permeability of its membrane. 4. 4. The positional distribution of saturated and unsaturated fatty acyl chains at the C-1 and C-2 positions of phosphatidylglycerol of A. laidlawii B appeared to be introduced during the first step of its biosynthesis, namely the formation of phosphatidic acid. 5. 5. A. laidlawii B was found to elongate palmitoleic acid