Isolation and characterization of bluensomycin biosynthetic genes from Streptomyces bluensis

The biosynthetic gene cluster for bluensomycin, a member of the aminoglycoside family of antibiotics, was isolated and characterized from the bluensomycin producing strain, Streptomyces bluensis ATCC27420. PCR primers were designed specifically to amplify a segment of the dTDP–glucose synthase gene based on its conserved sequences among several actinomycete strains. By screening a cosmid library using amplified PCR fragments, a 30-kb DNA fragment was isolated. Sequence analysis identified 15 open reading frames (ORFs), eight of which had previously been identified by Piepersberg et al. But seven are novel to this study. We demonstrated that one of these ORFs, blmA, confers resistance against the antibiotic dihydrostreptomycin, and another, blmD, encodes a dTDP–glucose synthase. These findings suggest that the isolated gene cluster is very likely to be responsible for the biosynthesis of bluensomycin.