Fig. 9.

Effect of the L. pneumophila surfactant on heterologous bacteria. As indicated, we spotted 10-fold dilutions of E. coli, P. aeruginosa, K. pneumoniae, B. subtilis, L. monocytogenes, and M. luteus onto BCYE agar plates that were free of L. pneumophila (Lp −), contained a nearby row of WT L. pneumophila that had grown and made a surfactant film (Lp 130b), or contained a row of a bbcI mutant that had grown but not produced a surfactant (Lp NU389). After incubation at 37°C for another day, the growth of the heterologous bacteria in the absence (Sfct −) or presence (Sfct +) of a surfactant was imaged. The results depicted here were observed in at least three independent experiments. On BCYE agar not containing L. pneumophila, the efficiencies of plating for these bacteria were the same whether the medium contained 0.5% agar or 1.5% agar, although plating on low-percentage-agar BCYE did result in greater spreading for those bacteria, such as P. aeruginosa, that are known to make a surfactant and/or undergo surface translocation (see Fig. S3 in the supplemental material).