Construct: Ecol\lacZrepo.4.3ΔGBS8 in which the remaining 3 gcm protein binding sites (RCCXXCAX) have been mutated (note - these are not perfect consensus sites). Sites mutated (position of relative to repo transcription start given in brackets): (-3859 to -3852) TCCCGCAT -> AAACGCAT; (-3660 to -3653) GCCCGCGT -> GAACGCGT; (-3649 to -3642) GCGCGCAT -> AAACGCAT.