Southern analysis of wild-type and Δpcd3 mutant strains of S. clavuligerus to search for paralogues of pcd. Samples of genomic DNA (2 μg) from wild-type and Δpcd3 mutant strains of S. clavuligerus were digested with either BbuI or NruI and separated on a 0.8% agarose gel. DNA fragments were transferred to a nylon sheet and hybridized with an approximately 1-kb radioactively labeled fragment internal to pcd. (A) Digested DNA fragments after electrophoresis and staining with ethidium bromide. (B) Nylon blot after hybridization with the labeled probe. Lanes 1 and 9, lambda DNA digested with PstI; lane 6, lambda DNA digested with BstEII; lanes 3 and 4, genomic DNA from wild-type cells digested with BbuI and NruI, respectively; lanes 7 and 8, genomic DNA from Δpcd3 mutant cells digested with BbuI and NruI, respectively; lane 10, probe DNA. Lanes 2 and 5 are empty.