L. pneumophila SSP and OMV fractions degrade protease and lipase substrates. (A) Protease activities detected by zymography with gelatin (from bovine skin). White clearing zones indicate gelatin degradation. (B) Proteolytic activities analyzed in a liquid assay using hide powder azure. The dotted line separates OMV samples, as the amounts tested are not comparable to the amounts in other samples. (C) Lipolytic activities determined by cleavage of the synthetic substrates NPP (□) and NPPC (▪). Again, the dotted line separates OMV samples, as the amounts examined were not comparable to other amounts. SN, bacterial culture supernatant; WC, whole bacterial cells; tp, total protein content per microliter of OMV fraction. The data are means and standard deviations of at least three independent experiments. A P value of <0.01 was considered significant.