Ether lipids in the cell membrane of Mycoplasma fermentans

Two new ether lipids, 1-O-alkyl/alkenyl-2-O-acyl-glycero-3-phosphocholine a nd its lyso form, 1-O-alkyl/alkenyl-glycero-3-phosphocholine, were identifi ed in the cell membrane of Mycoplasma fermentans using chemical analyses, G LC-MS, MALDI-TOF MS, and 1D and 2D NMR spectroscopy. The lipids are heterog eneous with respect to both acyl and alkyl/alkenyl residues. The acyl resid ues at position 2 of glycerol are hexadecanoyl and octadecanoyl in a molar ratio of 3.6 : 1 with a trace amount of octadecenoyl. The alkyl/alkenyl res idues at position 1 of glycerol are hexadecyl (78%), octadecyl (7%), octade cenyl (14%), and hexadecenyl (traces). In the octadecenyl residue, the doub le bond has a cis configuration and is located at either position 1' (plasm alogen-type lipid) or 9' in a ratio approximate to 1 : 1. This is the first report of the presence of alkyl and vinyl (alk-1'-enyl) ether lipids in th e cell membrane of aerobically grown mycoplasmas. Lipids of this type have been found in some Gram-positive bacteria, thus supporting the hypothesized close taxonomical relationship of these bacteria to mycoplasmas. The ether lipids of M. fermentans are structurally similar to platelet activating fa ctor; it was demonstrated that the 2-O-acetylated lyso form lipid can mimic platelet-activating factor activity in isolated perfused and ventilated ra t lungs.