RNA Polymerase Mutation Activates the Production of a Dormant Antibiotic 3,3′-Neotrehalosadiamine via an Autoinduction Mechanism in Bacillus subtilis

Abstract

Bacillus and Streptomyces species possess the ability to produce a variety of commercially important metabolites and extracellular enzymes. We previously demonstrated that antibiotic production in Streptomyces coelicolor A3(2) and Streptomyces lividans can be enhanced by RNA polymerase (RNAP) mutations selected for the rifampicin-resistant (Rifr) phenotype. Here, we have shown that the introduction of a certain Rifr rpoB mutation into a B. subtilis strain resulted in cells that over-produce an aminosugar antibiotic 3,3′-neotrehalosadiamine (NTD), the production of which is dormant in the wild-type strain. Mutational and recombinant gene expression analyses have revealed a polycistronic gene ntdABC (formally yhjLKJ) anda and a monocistronic gene ntdR (formally yhjM) as the NTD biosynthesis operon and a positive regulator for ntdABC, respectively. Analysis of transcriptional fusions to a lacZ reporter revealed that NTD acts as an autoinducer for its own biosynthesis genes via NtdR protein. Our results also showed that the Rifr rpoB mutation causes an increase in the activity of σA-dependent promoters including nt-dABC promoter. Therefore, we propose that unlike the wild-type RNAP, the mutant RNAP efficiently recognized the σ A-dependent promoters, resulting in the dramatic activation of the NTD biosynthesis pathway by an autoinduction mechanism.