Isolation and fatty acid analysis of neutral and polar lipids of the food bacterium Listeria monocytogenes

Listeria monocytogenes is a Gram-positive bacterium that causes meningitis, septicemia and death in humans. Found in low-acid cheeses, vegetables and meat, L. monocytogenes is resistant to osmotic and chill stress. Food handling practices that suppress microbial competitors can therefore promote its growth. In response to hyperosmotic or chill stress, L. monocytogenes accumulates the potent protectant glycine betaine from the medium, which decreases the lag time and increases the growth rate of the organism. The molecular basis for activation of glycine betaine transport by chill (7 °C), despite the expected membrane lipid phase transition, may reside in the lipid composition. The present research identified the lipids of L. monocytogenes. Extraction of total lipids yielded 7 ± 1 mg ml−1 wet cells, with a 5–6% phosphorus content. Polar lipids represented 64% of total lipids. There was a clear difference in the relative complexity of the fatty acids: neutral lipids were more varied and unsaturated fatty acids represented 19% of the total. Polar lipid fatty acids were primarily 15:anteiso (50%) and 17:anteiso (25%).