This work was supported by grant GM077596 (to H.Z.) from the US National Institutes of Health (NIH). Some of the data were collected in the Carl R. Woese Institute for Genomic Biology Core on a 600 MHz NMR funded by NIH grant number S10-RR028833, LC-MS at the MCB Metabolomics Center, and HRMS at the SCS Mass Spectrometry Laboratory. B.W. and F.G. dedicate this article to the memory of Keqian Yang, who made important contributions to their understanding of Streptomyces genetic regulation of secondary metabolism.