Southern hybridization showing insertion of the pTRK333-A, pTRK333-B, and pTRK333-C suicide plasmids into the chromosome of NCK203. Genomic DNA from NCK203 (lanes 1, 6, and 11), NCK203-A (lanes 2, 7, and 12), through NCK203-B (lanes 3, 8, and 13), or NCK203-D (lanes 4, 9, and 14) was digested with BamHI (lanes 1 through 4), PvuI (lanes 6 through 9), or SalI (lanes 11 through 14). Lanes 5 and 10 contained markers (one low-molecular-weight band in the marker lanes did hybridize with the probe). The Southern blot was probed with 32P-labeled pTRK333 DNA.