Tetrocarcin A (TCA),produced by Micromonospora chalcea NRRL 11289.is a spirotetronate antibiotic with potent antitumor activity and versatile modes of action.In this study,the biosynthetic gene cluster of TCA was cloned and localized to a 108-kb contiguous DNA region.We also propose the biosynthetic pathway of TCA Tetronolide biosynthesis involves the incorporafion of a 3-C unit with a polyketide intermediate to form the characteristic spirotetronate moiety and trans-decalin system.Further substitution of tetronofide with five deoxysugars (one being a deoxynitrosugar) was likely due to the activities of four glycosyltransferases.