Extracellular DNA degradation by pneumococcus EndA is independent of the competence regulon and cell autolysis.

(A) The rpsL PCR products (30 µg/ml) were exposed to the wild-type D39 and isogenic mutants for the indicated time intervals, or in the presence or absence of ATA or 2% choline chloride. The integrity of DNA was visualized by agarose gel electrophoresis. (B) Competence-deficient pneumococcal mutants degrade salmon sperm DNA efficiently. Pneumococcal cells were streaked onto the THB agar supplemented with salmon sperm DNA in the presence or absence of ATA or choline chloride. After 24 hr, DNA degradation was visualized by flooding the plates with HCl. Three independent experiments were performed for both A and B with similar results. The data from one typical experiment are shown.