FIG. 2.

Extracellular growth kinetics of L. pneumophila strains. Wild-type strain 130b (●) and mutant NU260 (□) were compared for growth in BYE (A), CDM (0.7 mM Mg²⁺) (B), and CDM with 0.05 mM (C), or 0.005 mM (D) Mg²⁺ cations. Growth was assessed by measuring the OD₆₆₀ of triplicate cultures at various times of incubation. Asterisks indicate significant differences (P < 0.05; Student's t test) between the 130b and NU260 cultures. Standard deviations are shown, but the error bars are too small to be observed in panels A to C. This experiment was performed in triplicate with comparable results, and representative data are presented here.