Genetic manipulation of spiramycin-producing strain Streptomyces ambofaciens ATCC 23877 by φC31 Att/Int system-based vectors results in a significant reduction of antibiotic production

The genus Streptomyces produces about two-thirds of naturally occurring antibiotics and many other biologically active secondary metabolites. The genetic manipulation of Streptomycetes is often labor and time intensive due to their large genome and complex development. Much progress has been made to develop gene transfer methods useful to construct antibiotic-producing strains with improved properties. The φC31 Att/Int system is an integration system that has been widely used to produce stable recombinants in Actinomycetes and its integration site is an attB site located in a pirin-like gene (pirA) of the bacterial chromosome. In this study we demonstrate that the integration of φC31 DNA in Streptomyces ambofaciens ATCC 23877 chromosome results in a significantly reduced spiramycin production and causes some phenotypic changes. With the aim to get insight into the molecular mechanisms underlying these effects we have analyzed the transcriptome and proteome of the wild type strain and a derivative strain harboring pTYM-18 vector plasmid integrated into the pirA gene. Evidence is provided that inactivation of the pirA gene by plasmid integration leads to dramatic gene expression changes with marked effects on central carbon and energy metabolism, high sensitivity to oxidative injury and repression of polyketide antibiotic production.