Mycobacteria: Bugs and Bugbears

Mycobacteria are gram-positive, rod-shaped bacteria of the Actmomycete family, and therefore are most closely related to the nocardia, corynebacteria, and streptomyces. Their most characteristic feature is their complex cell envelope, containing a high percentage of lipids, which include the large-branched mycolic acids. This envelope makes the bacteria resistant to breakage and relatively impermeable to antibiotics, and is responsible for the acid-fast staining property used to identify the organisms. The genomic DNA contains a high guanme plus cytosine (GC) content, ranging from 58–69% (), which affects the utility of Escherichia coli as a surrogate genetic host.