FIG. 1.

Intracellular growth kinetics of GK11 and AA100 (wild-type L. pneumophila) in U937 macrophage-like cells (A) and WI-26 alveolar epithelial cells (B). Strain K9 is a cosmid-complemented clone of GK11. Experiments were performed in triplicate and repeated at least three times. The data are from a representative experiment. Error bars represent standard deviation of the mean; some of the error bars are too small to be seen. ∗, significantly fewer intracellular bacteria than in wild-type (AA100)-infected cells, based on Student's t test (P < 0.05).