Environmental DNA-derived cosmid clones containing type II polyketide synthase genes were screened for the ability to produce clone-specific metabolites in Streptomyces. One of the Streptomyces recombinants produces erdacin, a novel polyketide with a previously unknown pentacyclic skeleton. Erdacin provides tangible evidence that environmental DNA gene clusters are likely to encode the biosynthesis of molecules that are substantively different from those that have been identified using culture-based strategies.