In Myxococcus xanthus, all known carotenogenic genes are grouped together in the gene cluster carB–carA, except for one, crtIb (previously namedcarC). We show here that the first three genes of the carBoperon, crtE, crtIa, and crtB, encode a geranygeranyl synthase, a phytoene desatur-ase, and a phytoene synthase, respectively.