Natamycin Efflux System And Its Regulation Mechanism In Streptomyce Chattanoogensis

Sirepiomyces is well-known for its use in the production of considerable natural products with high pharmacological and commercial values including most of the antibiotics. These antibiotic-producing microorganisms have evolved several self-resistance mechanisms to prevent autotoxicity. Overexpression of the specific transporter to improve the efflux of toxic antibiotics has been showed to be one of the most important and intrinsic resistance strategies in many Streptomyces strains. Understanding of the biosynthesis, regulation and modificationof antibiotics have advanced considerably in the past two decades. The characterization of the antibiotics efflux mechanism has just been started. In this work, the natamycin-related efflux mechanism has been carefully studied and the regulation mechanism of the efflux pump has also been reported.We identify two ATP-Binding Cassette transporters-encoding genes, scnA and scnB. from the natamycin biosynthetic gene cluster and show that ScnA/ScnB are not the only exporters involving in natamycin efflux. Two other efflux pump, Mfsl and Nepl/Il was characterized from the microarray data. The deduced product of mfsl is predicted to be a major facilitator superfamily (MFS) protein. Our results demonstrated that the Mfsl and Nep?/? could form a collaborative and complementary transport system for natamycin efflux. Besides, ScnA/ScnB and Mfsl also participate in exporting the direct natamycin precursor 4.5-de-epoxynatamycin, which is actually more toxic to S. Chattanoongensis L10 than natamycin. The phylogenetic analysis also reveals that the homologus of Mfs1 and Nep?/? might be taken as a commonly self-resistance strategy in some macrolide antibiotic producing strains.In addition, the regulation pattern of this efflux system has been reported. The pathway specific regulator ScnRII could positively regulate the expression of scnA/scnB. Mfol can respond to the intracellular accumulation of natamycin related metabolites and induce the overexpression of Mfs1 to act in a stress response role in order to decrease cell damage. Several experiments were performed to investigate the response mechanism of Nep?/?. However, the direct regulators were still not found.Taken together, in this study we not only elaborate a novel collaborative transport system of natamycin-related molecules and reveal its regulation mechanism for the first time, but also provides an interesting example of a self-resistance mechanism in an antibiotic-producing strain. Our research will provide theoretical basis for enhanced production of natamycin and hence of both academic value and commercial interest.