Increasing Demeclocycline Production in Streptomyces aureofaciens by Manipulating the Expression of a Novel SARP Family Regulator and Its Genes

Demeclocycline (DMCTC), a tetracycline derivative antibiotic produced by Streptomyces aureofaciens , has attracted attention owing to its high bioavailability, prolonged maintenance of a therapeutic concentration, and greater efficacy against many infectious microorganisms. However, the productivity of the DMCTC-producing strains has remained low. Thus, it is necessary to identify gene-knockout or amplification targets to increase DMCTC production. Here, we demonstrated that ctcB , which encodes a Streptomyces antibiotic regulatory protein (SARP), and ctcC , which encodes a resistance gene, positively regulate the biosynthesis of DMCTC in S. aureofaciens strain DT1. In particular, overexpression of the ctcB gene in S. aureofaciens DT1 significantly enhanced DMCTC production, resulting in increased expression of ctcG, ctcN, ctcQ, ctcH, ctcV , and ctcC. The deletion of ctcB dramatically reduced the DMCTC level, implying that CtcB is an activator of DMCTC biosynthesis. Although overexpression of the ctcC , which encodes a ribosomal protection protein, enhancing DMCTC biosynthesis in S. aureofaciens DT1, the improvement was limited compared with that achieved by ctcB overexpression. This is the first study to identify the role of ctcB and ctcC in DMCTC accumulation; these genes may also be ideal candidate targets for facilitating DMCTC production by other Streptomyces strains.