Amplification of the entire kanamycin biosynthetic gene cluster during empirical strain improvement of Streptomyces kanamyceticus

• DOI: 10.1073/pnas.0603251103
• Publication Date: 2006-06-10T00:48:51Z
• Authors: Koji Yanai; Takeshi Murakami; Mervyn Bibb
• Keywords: 0303 health sciences; Base Sequence; Molecular Sequence Data; Gene Amplification; Gene Dosage; Gene Expression Regulation, Bacterial; Chromosomes, Bacterial; Streptomyces; 03 medical and health sciences; Kanamycin; Multigene Family; Mutation; Gene Deletion

Streptomyces kanamyceticus 12-6 is a derivative of the wild-type strain developed for industrial kanamycin (Km) production. Southern analysis and DNA sequencing revealed amplification of a large genomic segment including the entire Km biosynthetic gene cluster in the chromosome of strain 12-6. At 145 kb, the amplifiable unit of DNA (AUD) is the largest AUD reported in Streptomyces . Striking repetitive DNA sequences belonging to the clustered regularly interspaced short palindromic repeats family were found in the AUD and may play a role in its amplification. Strain 12-6 contains a mixture of different chromosomes with varying numbers of AUDs, sometimes exceeding 36 copies and producing an amplified region >5.7 Mb. The level of Km production depended on the copy number of the Km biosynthetic gene cluster, suggesting that DNA amplification occurred during strain improvement as a consequence of selection for increased Km resistance. Amplification of DNA segments including entire antibiotic biosynthetic gene clusters might be a common mechanism leading to increased antibiotic production in industrial strains.