Using pulsed\|field gel electrophoresis (PFGE),two indigenous large plasmids were isolated from Streptomyces T8 4.Two dimentional PFGE revealed that both plasmids were linear molecules.By parallel electrophoresis with linear plasmids of known sizes,the two linear plasmids were estimated to be approximately 230kb and 90kb,which were designated as pHZ1000 and pHZ1001,respectively.Both plasmids could be transferred into S.lividans ZX1 by conjugation,which is detectable by “pock”formation.Five S.lividans ZX1 derivatives which carry one or two plasmids were isolated and characterized by Southern hybridization and PFGE.
