MoO-18
SPECIATION OF POLYUNSATURATED FATTY ACIDS IN THE PHOSPHOLIPIDS OF AN ANTARCTIC BACTERIUM BY FAST ATOM BOMBARDMENT TANDEM MASS SPECTROMETRY
David S. Nichols1,2, Noel W. Davies3 and Peter D. Nichols1,4
1Antarctic CRC, 2Department of Agricultural Science and 3Central Science Laboratory, University of Tasmania, GPO Box 252-54, Hobart, Tasmania 7001, Australia
4CSIRO Division of Oceanography, Marine Laboratories, GPO Box 1538, Hobart, Tasmania 7001, Australia.
The use of fast atom bombardment-mass spectrometry (FAB-MS) has become a powerful technique for the structural analysis of complex lipids. Determination of phospholipid species molecular ions, together with the known fatty acid composition of a bacterium, allows the presumptive identification of the acyl chain pairing associated with each phospholipid species. This approach obviates the need for complex lipid fractionation and derivatisation procedures. The bacterial strain ACAM 456 was isolated from sea ice collected in Prydz Bay, Eastern Antarctica. Lipid analysis indicated the bacterium contained phosphotidylethanolamine (PE) and phosphatidylglycerol (PG) as major phospholipids. Eicosapentaenoic acid [20:5w3, EPA] was present within both phospholipid and free fatty acid fractions but was concentrated within the PG fraction, while branched-chain fatty acids were concentrated in PE.
Negative ion fast atom bombardment-tandem mass spectrometry (FAB-MS-MS) analysis of the total solvent extract showed a specific association of EPA with the acyl residues i15:0/15:0, 16:0 and 16:1 in both phospholipid classes. Association with 17:1 was specific to PG, while association of EPA with i13:0/13:0 and i14:0/14:0 was specific to PE. The potential exists for the application of this technique to the identification of bacterial-associated PUFA from environmental samples. The detection of phospholipid molecular species from environmental samples in which EPA is associated with branched-acyl chains, such as i13:0, would indicate the presence of bacterial PUFA-producing cells.