No abstract

Comprehensive Summary The anti‐tuberculous rifamycins belong to naphthalenic ansamycin based on the structure of aromatic chromophore. Herein, we explored the post‐polyketide synthase (PKS) modifications in the biosynthesis of 16‐demethyl‐rifamycins via gene knockout, complementation and in vitro enzyme assays. The collective evidences showed that i) the aromatization of 8‐hydroxyl‐7,8‐dihydronaphtoquinone was accomplished by the combined action of two dehydrogenases, RifS and RifT; ii) the acetylation and methylation of the macrocycle was carried out on naphthoquinone intermediates in preference to naphthol, by Rif‐Orf20 and Rif‐Orf14, respectively; iii) the presence of RifS/T homologs in ansamycin biosynthetic gene clusters corresponds to the dehydrogenation aromatization mode of dihydronaphthalene. These findings cast new insights into the naphthalene formation and post‐PKS modification of ansamycins.