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Microbiology. 2000 Mar;146 ( Pt 3):611-9.

Identification of a gene cluster for antibacterial polyketide-derived antibiotic biosynthesis in the nystatin producer Streptomyces noursei ATCC 11455.

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  • 1UNIGEN Center for Molecular Biology and Department of Biotechnology, NTNU, Trondheim, Norway. sergey.zotchev@chembio.ntnu.no


Streptomyces noursei ATCC 11455 produces the antifungal polyene antibiotic nystatin containing the deoxysugar moiety mycosamine. Part of the deoxythymidyl diphosphate (TDP)-glucose dehydratase gene (gdhA) known to be involved in deoxysugar biosynthesis was amplified by PCR from genomic DNA of S. noursei ATCC 11455. A gene library for S. noursei was made and screened with the gdhA probe. Several overlapping phage clones covering about 30 kb of the S. noursei genome were physically mapped. A partial DNA sequencing analysis of this region resulted in the identification of several putative genes typical of macrolide antibiotic biosynthetic gene clusters. A gene-transfer system for 5. noursei has been established, and gene deletion or disruption experiments within the putative biosynthetic gene cluster were performed. All of the knock-out mutants retained the ability to produce nystatin, suggesting that the identified gene cluster is not involved in biosynthesis of this antibiotic. Culture extracts from the wild-type strain and three knock-out mutants were analysed by TLC followed by a bioassay against Micrococcus luteus. Two antibacterial compounds were found to be synthesized by the wild-type strain while only one was produced by the mutants. This provided evidence for the involvement of the identified gene cluster in the biosynthesis of a presumably novel antibacterial macrolide antibiotic in S. noursei.

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