FIG. 3.

Comparison of strains EK4166 and H4 with respect to the level of competence-induced release of cytoplasmic β-galactosidase. The lytA gene of strain H4 has been disrupted, but otherwise the strain is identical to EK4166. At different cell densities (OD₅₅₀s of 0.1 to 0.7), samples were withdrawn and induced to competence by adding 250 ng of synthetic CSP-1/ml. After 30 min at 37°C, cell-free supernatants were prepared and assayed for β-galactosidase activity. Corresponding uninduced samples were run in parallel as negative controls. Closed squares, activity in supernatants from CSP-1-induced EK4166 cells; open squares, activity in supernatants from uninduced EK4166 cells; closed circles, activity in supernatants from CSP-1-induced H4 cells; open circles, activity in supernatants from uninduced H4 cells. The β-galactosidase activity is given in Miller units, and amounts shown are the means ± standard errors of results for triplicate samples.