Amphotericin biosynthesis in Streptomyces nodosus: deductions from analysis of polyketide synthase and late genes

Background: The polyene macrolide amphotericin B is produced by Streptomyce s nodosus ATCC14899. Amphotericin B is a potent antifungal antibiotic and h as activity against some viruses, protozoans and prions. Treatment of syste mic fungal infections with amphotericin B is complicated by its low water-s olubility and side effects which include severe nephrotoxicity. Analogues w ith improved properties could be generated by manipulating amphotericin bio synthetic genes in S. nodosus. Results: A large polyketide synthase gene cluster was cloned from total cel lular DNA of S. nodosus. Nucleotide sequence analysis of 113 193 bp of this region revealed six large polyketide synthase genes as well as genes for t wo cytochrome P450 enzymes, two ABC transporter proteins, and genes involve d in biosynthesis and attachment of mycosamine. Phage KC515-mediated gene d isruption was used to show that this region is involved in amphotericin pro duction. Conclusions: The availability of these genes and the development of a metho d for gene disruption and replacement in S. nodosus should allow production of novel amphotericins. A panel of analogues could lead to identification of derivatives with increased solubility, improved biological activity and reduced toxicity. (C) 2001 Elsevier Science Ltd. All rights reserved.