Fig. 2.

Surface translocation by L. pneumophila mutants when spotted onto film produced by wild-type legionellae. WT 130b was inoculated onto the center of a BCYE plate containing 0.5% agar at 30°C. After 10 days, when a layer of surface film was clearly evident beyond the spreading legionellae, a 10-μl aliquot of the WT, mutant NU388, mutant NU389, and mutant NU390 was spotted onto the agar surface either in the surfactant-covered area (“+”) or at a point outside of it but still equidistant from the center of WT growth (“−” area). After 3 days of further incubation, images were taken in order to visualize any differences in spreading. The white lines show the film front. The images are representative of three independent experiments.