PFGE (A) and Southern analysis (B) of KTR9 and derived mutant strains. A biotin-labeled 683-bp DNA fragment, specific for pGKT2, was used to probe a PFGE gel of uncut and XbaI-digested DNA samples from wild-type and mutant KTR9 strains. Lanes: 2, uncut KTR9; 3, uncut deletion mutant 1; 4, uncut deletion mutant 2; 5, cut KTR9; 6, cut deletion mutant 1; 7, cut deletion mutant 1. Lane L shows molecular mass markers, with sizes in kilodaltons at the left.