Isolation and Characterization of Phosphatidylglycerol from Staphylococcus aureus

Catherine Reed

Abstract

Staphylococcus aureus (S. aureus) is a bacteria that can potentially cause a fatal infection if it gets into the body, especially the bloodstream. Phosphatidylglycerol (PG) is a main component of the lipid bilayer of S. aureus and may play a role in the bacteria’s immunity to its own toxins. In this study, large cultures of S. aureus were grown in order to extract phospholipids from the bacteria cells. The resulting extracts were analyzed by both ¹H- and ³¹P-NMR. Separation of the lipids into polar and non polar fractions, followed by ¹H- and ³¹P-NMR analyses, served as an initial purification of the polar phospholipids. Preparative TLC was performed on the phospholipid samples to purify phosphatidylglycerols, which were then analyzed by ¹H- and ³¹P-NMR. Fatty acids were cleaved from the phospholipids and converted to fatty acid methyl esters (FAMEs), which were analyzed by both GC-FID and GC-MS. GC-FID was used for quantitative analysis of the FAMEs and the relative percent areas showed that the separated fractions from the preparative TLC had similar major fatty acids. GC-MS was utilized to propose identifications of the fatty acids by their molecular ion, fragmentation patterns, and retention times. The results obtained from the NMR, GC-FID, and GC-MS analyses suggest that S. aureus phosphatidylglycerols were purified, but not separated into single molecular species.