The polar lipid fatty acid (PLFA) profiles of invertebrates living in chemosynthetic communities can indicate the degree to which these animals depend on specific types of bacteria. To identify the nutritional sources of various species from deep-sea hydrothermal vents of the Mid-Atlantic Ridge, a Principal Component Analysis was performed using individual PLFA profiles as descriptors. Two associations representing different feeding groups were identified: (i) mussels, commensal polychaetes and gastropods, (ii) shrimps and crabs. The first association relies more on sulphide-oxidizing bacteria, while the second one has more anaerobic sulphate-reducing bacteria biomarkers. Other small invertebrates reveal different diets. The polychaete Amathys lutzi shows the most diversified bacterial diet, with fatty acid biomarkers from both S-oxidizing and S-reducing bacteria.