Phospholipids and cholesterol in the cell membrane of representative Mycoplasma species.
|Mycoplasma species|| PL||C||CE||C/PL (molar ratio)||Reference|
(nmole/mg membrane protein)|
|M. hyorhinis was grown in a modified Hayflick’s medium  to the mid-exponential phase of growth, and isolated membranes were prepared as previously described . Lipids were extracted from membrane preparations by the method of Bligh and Dyer . Unesterified cholesterol, cholesterol esters, and phospholipids were separated on Merck Silica Gel G glass plates using benzene : diethyl ether : ethanol : acetic acid (50 : 40 : 2 : 0.2). The unesterified cholesterol and the cholesterol esters spots were extracted with chloroform for 30 min at room temperature, and the sterol content was determined by the phthaldialdehyde method . Phosphorus in the phospholipid spot was determined by the method of Zhou and Arthur  using KH2PO4 as a standard. In brief, the spots were scraped from the plate into test tubes, digested with 0.5 mL of 70% perchloric acid (HClO4), and transferred into a 2 mL solution containing malachite green (0.2%) and ammonium molybdate (4%) in Tween-20 (1.5% w/v) and 5 M HCl (3 : 1 by vol.). The results are the average of three independent experiments using different batches of cells. PL: total phospholipids; TC: total cholesterol; C: unesterified cholesterol; CE: cholesterol esters.|