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

BACKGROUND

The polyene macrolide amphotericin B is produced by Streptomyces nodosus ATCC14899. Amphotericin B is a potent antifungal antibiotic and has activity against some viruses, protozoans and prions. Treatment of systemic fungal infections with amphotericin B is complicated by its low water-solubility and side effects which include severe nephrotoxicity. Analogues with improved properties could be generated by manipulating amphotericin biosynthetic genes in S. nodosus.

RESULTS

A large polyketide synthase gene cluster was cloned from total cellular DNA of S. nodosus. Nucleotide sequence analysis of 113193 bp of this region revealed six large polyketide synthase genes as well as genes for two cytochrome P450 enzymes, two ABC transporter proteins, and genes involved in biosynthesis and attachment of mycosamine. Phage KC515-mediated gene disruption was used to show that this region is involved in amphotericin production.

CONCLUSIONS

The availability of these genes and the development of a method 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.