FIG. 4.
Induction of competence in L. pneumophila. (Top) Viable counts before addition of DNA. Sample numbers correspond to samples taken at the time points indicated in the bottom panel. (Bottom) L. pneumophila BS200 chromosomal DNA (400 μg/ml) was added to cultures at the time points indicated, and the cultures were allowed to incubate for an additional 2 days before transformation frequency was determined. No transformants were detected after addition of DNA at days 0 and 6. The limit of detection for transformation frequency was 10−9. Error bars indicate standard deviations.