Isolation and characterization of linear plasmids from lankacidin-producing Streptomyces species

Streptomyces rochei 7434AN4, a producer of lankacidin and lankamycin contains three large linear plasmids, pSLA2-L (200 kb), M (100 kb), and S (17 kb). Studies on the mutants of 7434AN4 having a different plasmid profile showed a parallel relationship between the presence of pSLA2-L and the production of both lankacidin and lankamycin. When pSLA2-L was transferred by protoplast fusion to S. rochei 2-39, a non-antibiotic-producing mutant of 7434AN4 which contained no detectable plasmid, the fusants gained the capacity to produce both antibiotics. From the physical maps of pSLA2-L and pSLA2-L1, a deletion plasmid (160 kb) of pSLA2-L, the latter plasmid was determined to contain a symmetrical linear repeat composed of the right 80-kb part of pSLA2-L. Four other lankacidin-producing Streptomyces strains were also found to have distinctive large linear plasmids which hybridized with the pSLA2-L probe. These results support the involvement of pSLA2-L in the production of lankacidin and lankamycin in S. rochei 7434AN4.