Fig. 2

PFGE of P2niaD18 and its derivatives indicate loss of one cluster copy. a PmeI restriction map of the duplicated penicillin cluster. b PFGE was performed using restriction enzyme PmeI and a genomic fragment comprising the pcbC gene as a probe. For P2niaD18, this results in two signals with the size of 246.2 kb and 97 kb (a, b), thus indicating the duplication as proposed in a. During the generation of a marker-free ΔPcku70 strain, the extra copy of the penicillin cluster was lost in T1 and its derivatives. In contrast, T17 and its derivatives still carry both copies (c). In ΔpcbC, all copies of the pcbC gene were deleted, however a signal still occurs since the probe comprises the gene, the adjacent promotor region, and part of the flanking penDE gene. c Genealogy of penicillin production strains used in this study. The copy number of the penicillin gene cluster is given in red