FIG. 6.

Mother cell DNA after cell lysis. (A) DNase activity of T₉ cell culture medium from strains 168 (wild type [WT]), NUCBs (ΔnucB), and CWLBCH (ΔcwlBCH). Culture of each strain was centrifuged, and cells in the supernatant were removed by filtration (0.22 μm). B. subtilis chromosomal DNA (0.6 μg) was added to 8 μl of each filtered supernatant (lane 1) or diluted supernatant (1:10, lane 2; 1:100, lane 3) isolated from T₉ cultures, incubated at 37°C for 1 h, and then analyzed by ethidium bromide-stained 0.8% agarose electrophoresis. (B) Detection of mother cell DNA after lysis. The mother cell-specific DNA (the sigK gene) was amplified by PCR with primers sigKF and sigKR and analyzed by 0.8% agarose electrophoresis. The template DNA sample consisted of 1, 1/10, or 1/100 μl of the filtered supernatant (WT, ΔnucB, and ΔcwlBH). PCR amplification was performed with 30 cycles of denaturation at 93°C for 1 min, annealing at 55°C for 1 min, and extension at 72°C for 2 min.