Mycolic acids are long-chain fatty acids found in the cell walls of certain bacteria, particularly in the genus Mycobacterium. These unique lipids contribute to the bacteria's resistance to environmental stresses, antibiotics, and the host's immune system. Mycolic acids play a crucial role in the formation of a waxy layer that protects the bacteria. In addition to Mycobacterium tuberculosis, which causes tuberculosis, mycolic acids are also present in other pathogenic species. Their presence is a key factor in the identification and classification of these bacteria, making them important in microbiology and medical research.