PLFA stands for phospholipid fatty acids. These fatty acids are found in the cell membranes of living organisms. Different groups of organisms have a unique composition of these (PLFA) fatty acids. Measuring and quantifying the PLFAs can provide a fingerprint of the soil food web. For example, the cell membranes of fungi consist of different PLFAs to those associated with bacteria. The PLFAs present are measured and quantified using a gas chromotograph-MS.