Figure A1.

Analysis of degradation of salmon sperm DNA by S. pneumoniae and K. pneumoniae. Salmon sperm DNA (2 μg) was treated with either bacterial pellet (10⁷ cells) or double-filtered supernatant (3 μl) of S. pneumoniae 19F or K. pneumoniae K15 at 37°C for 1 h in DNase buffer (10 mM Tris, 3 mM MgCl₂, 5 mM CaCl₂, pH 7.4), and the reaction was stopped with 0.5 M EDTA. The samples were then subjected to 1% agarose gel electrophoresis. Lanes: (1) DNA ladder. Salmon sperm DNA was incubated with (2) DNase buffer; (3) DNA alone; (4) BHI broth; (5) S. pneumoniae pellet; (6) S. pneumoniae supernatant; (7) LB broth; (8) K. pneumoniae pellet; and (9) K. pneumoniae supernatant. The DNA smearing below 500 bp in lanes 5 and 6 revealed that salmon sperm DNA was digested by both pellet and supernatant of S. pneumoniae, indicating secreted DNase activity. However, K. pneumoniae did not digest the DNA as shown by relatively intact salmon sperm DNAs.