Spiramycin, a 16-membered macrolide antibiotic used in human medicine, is produced by Streptomyces ambofaciens; it comprises a polyketide lactone, platenolide, to which three deoxyhexose sugars are attached. In order to characterize the gene cluster governing the biosynthesis of spiramycin, several overlapping cosmids were isolated from an S. ambofaciens gene library, by hybridization with vari...