Genome-Driven Discovery of Hygrocins in Streptomyces rapamycinicus .

Ansamycins, represented by the antituberculosis drug rifamycin, are an important family of natural products. To obtain new ansamycins, Streptomyces rapamycinicus IMET 43975 harboring an ansamycin biosynthetic gene cluster was fermented in a 50 L scale, and subsequent purification work led to the isolation of five known and four new analogues, where hygrocin W ( 2 ) belongs to benzoquinonoid ansamycins, and the other three hygrocins, hygrocins X-Z ( 6 - 8 ), are new seco-hygrocins. The structures of ansamycins ( 1 - 8 ) were determined by the analysis of spectroscopic (1D/2D NMR and ECD) and MS spectrometric data. The Baeyer-Villiger enzyme which catalyzed the ester formation in the ansa-ring was confirmed through in vivo CRISPR base editing. The discovery of these compounds further enriches the structural diversity of ansamycins.