What is a defining feature of mycolic acid in bacteria?

Mycolic acid is a defining feature of the cell walls of acid-fast bacteria, such as members of the genus Mycobacterium. This waxy substance consists of long-chain fatty acids, which contribute to the distinctive characteristics of acid-fast bacteria.

The presence of mycolic acids in the cell wall makes these bacteria resistant to certain chemical and physical stresses, including desiccation and the action of antibiotics, due to its hydrophobic nature. Mycolic acids contribute to the overall impermeability of the cell wall, which is why acid-fast bacteria hold onto dye during staining procedures, unlike non-acid-fast bacteria.

This unique feature is crucial for the survival and pathogenicity of bacteria like Mycobacterium tuberculosis, the causative agent of tuberculosis. The waxy layer also plays a role in evading the host immune response, providing another layer of protection for these bacteria in hostile environments.