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The PABA synthetase gene of S. lividans was obtained by shotgun cloning of S. lividans 66 genomic DNA into E. coli AB3295 (pabB) using pBR322 as a vector. A 4.8-kb BamHI fragment that complemented the pabA and pabB mutations in E. coli was obtained. Complementation of both mutations was also observed when the same fragment was cloned in the opposite orientation with respect to the vector. The gene was localized on a 7.2-kb BamHI : SstI segment by subcloning into pTZ18R. The 7.2-kb fragment complemented the pab mutation in S. lividans J610 when it was introduced on a Streptomyces - …
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In a galactose-isoleucine medium at 37°C Streptomyces venezuelae ISP5230 produces a group of related pigment antibiotics. The structures of these products place them in the family of polyketide secondary metabolites (S. Ayers, personal communication). A library of S. venezuelae ISP5230 genomic DNA was prepared in a lambda replacement vector and probed with the actI gene for polyketide synthase from Streptomyces coelicolor A3(2). A clone, possessing a 9.3-kb insert of S. venezuelae DNA, hybridized strongly to actI. The actI-hybridizing region was localized to a 1.8-kb SstI fragment at one end of the insert. The actIII gene encoding the polyketide reductase of …
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Against the virginiamycin group of antibiotics, to which etamycin belongs, two mechanisms of resistance are known - enzymic inactivation and target site modification. No etamycin inactivating activity was detected either extracellularly or in cell extracts of S. griseoviridis. Since target site modification in MLS-type antibiotics (which include etamycin and erythromycin) involves 23S rRNA modification, an internal fragment of the previously characterized ermE gene which confers erythromycin resistance on the erythromycin producer, was used to probe for hybridizing DNA fragments in an S. griseoviridis genomic library. A lambda clone containing 17 kb of S. griseoviridis DNA was thereby detected. The fragment …
