Structural analysis of the giant linear plasmid SCP1 in various Streptomyces coelicolor strains

The methylenomycin biosynthetic gene cluster was previously shown to be present on the 350 kb giant linear plasmid SCP1. The structures of SCPl in various Streptomyces coelicolor A3(2) strains were analysed by pulsed field gel electrophoresis (PFGE). S. coelicolor A3(2) strains 1147, M138 and M146, previously genetically characterized as SCPl+, contained the free form of SCP1. S. coelicolor 1984 and 2106, earlier characterized as SCP1’-cysB and a stable cysD donor respectively, were found to contain very large linear plasmids, 550 kb and 1700 kb in size. Strain JCM4979, another SCPl+ derivative of A3(2), had a series of SCP1-related linear plasmids of 390-630 kb. The integrated states of SCPl in S. coelicolor SCPl-NF strains, an NF-like strain and a stable pabA donor were confirmed by PFGE, which revealed a lack of the intact SCPl termini. In addition, a 70 kb linear plasmid was found in Streptomyces viofaceoruber SANK95570, another methylenomycin producer. However, the plasmid was shown by hybridization to a methylenomycin resistance gene not to carry the methylenomycin gene cluster of this strain