Novel polyene polyketides, their pharmaceutically acceptable salts, prodrugs and derivatives have been found to have antibiotic activity. One method for obtaining the compounds is by cultivation of Amycolatopsis orientalis ATCC.TM. 43491 or a mutant or variant such as the strain IDAC-220604-1. Another method for obtaining the compounds is post-biosynthesis chemical modification of the compounds obtained by cultivation. Novel polynucleotide sequences and encoded proteins for the biosynthesis of the polyene polyketides are also presented.