Phthiocerol and phthiodiolone dimycocerosates (DIMs) and phenolic gly-colipids (PGLs) are complex lipids located at the cell surface ofMycobacte-rium tuberculosis that play a key role in the pathogenicity of tuberculosis. Most of the genes involved in the biosynthesis of these compounds are clustered on a region of the M. tuberculosischromosome, the so-called DIM + PGL locus.