Figure 1.

Competence-induced release of cytoplasmic β-galactosidase from S. pneumoniae cells. Samples of the bacterial culture were collected at different cell densities (OD₅₅₀ = 0.1–0.8) and induced to competence by adding 250 ng/ml of synthetic CSP-1. Corresponding uninduced samples were collected as negative controls. A cell lysate (lysed cells plus supernatant) and cell-free supernatant were made from each sample, and the β-galactosidase activity was measured in both. Closed circles, cell lysates from competent cells; closed squares, cell lysates from noncompetent cells; open circles, supernatants from competent cells; open squares, supernatants from noncompetent cells. β-Galactosidase activities are given in Miller units.