FIG 1.

The surface translocation of L. pneumophila depends on Mip and PpiB. (A to D) L. pneumophila wild-type (WT) (A), Δmip (B), ΔppiB (C), and Δmip ΔppiB (ΔΔ) (D) strains were grown on BCYE plates containing 0.5% agar at 30°C for 7, 14, and 21 days (d). For each time point and strain, a representative picture from three independent experiments performed in triplicate is presented on the left, while the boundaries of the surfactant film are highlighted on the right. (E) Quantification of the spreading area of the strains revealed no significant differences over 21 days. (F) In the case of the surfactant area, PPIase-negative Δmip and Δmip ΔppiB strains showed a significant decrease in the secretion of surfactants. (G to I) The defect in the formation of a surfactant film was complemented by introducing the respective gene in the single-gene-knockout mutants. (J and K) This was confirmed by quantitative measurement of the spreading and surfactant film areas. Shown are the means and standard deviations from three experiments performed in duplicate. Statistical significance was calculated using an unpaired Student's t test (*, P ≤ 0.05; **, P ≤ 0.01; ***, P ≤ 0.001; n.s., not significant).