Which characteristic is a notable feature of mycobacteria?

Mycobacteria are distinguished by their unique cell wall structure, which contains high amounts of mycolic acid. This waxy substance is a significant feature that contributes to the bacteria's resistance to desiccation and provides protection from certain antibacterial agents, making them harder to stain with ordinary methods. The presence of mycolic acid in the cell wall also grants mycobacteria their characteristic slow growth rate and virulence. This unique feature is key in identifying and classifying mycobacteria, such as Mycobacterium tuberculosis, which is responsible for tuberculosis. Thus, the waxy cell wall due to mycolic acid is a defining characteristic that sets mycobacteria apart from other bacteria.