FIG. 7.

(A) ΔdotI mutation causes defective intracellular growth in phorbol ester-treated U937 cells over 72 h, and this defect is complemented by dotI in trans. Growth of L. pneumophila was monitored for 72 h. Values and error bars represent the average of triplicate samples from a typical experiment (performed at least twice) and their standard deviations. Strains: Lp01 (dot⁺; ▵), HL019 (dot⁺, pMS8; ▴), HL056 (dotI; □), HL057 (dotI, pMS8; ┘), and HL059 (dotI, pI1; ▪). (B) ΔdotI mutants colocalize with LAMP-1. Mouse bone marrow-derived macrophages were incubated with mutant or virulent strains for 2 h, fixed, and stained for intracellular versus extracellular bacteria and LAMP-1 colocalization. Data were collected from 100 intracellular bacteria. Percent LAMP-1 positive was calculated by dividing the number of intracellular rod-shaped bacteria colocalizing with LAMP-1 by the total number of intracellular rod-shaped bacteria scored. Values shown are the averages of duplicate samples from two identical experiments (four samples in total) and their standard deviations.