FIGURE 5.

Cell-associated PLA activity within clinical isolates of L. pneumophila and PlaB-like enzyme properties of non-pneumophila Legionellae. A, cell lysates of various clinical isolates (Table 1) were incubated with PLA (DPPG and DPPC) and LPLA (MPLPG and MPLPC) substrates. Nine clinical isolates were compared with L. pneumophila Corby and with the water conduit strain Legionella 257. B, determination of released fatty acids by L. pneumophila 130b and 12 different non-pneumophila strains. Cells were grown to an A₆₆₀ of 1.5, pelleted, lysed, and added to different lipids, followed by quantification of released fatty acids. C, cell lysates of E. coli DH5α expressing either L. pneumophila or L. spiritensis plaB were incubated with different lipid substrates, and released fatty acids were quantified. DPPC hydrolysis of L. spiritensis PlaB was significantly decreased (p < 0.05) compared with L. pneumophila Corby PlaB. D, lysis of human red blood cells by E. coli strains as mentioned in C was measured at 415 nm after the bacteria-cell suspension was incubated for 4 h at 37 °C. EV, empty vector pBCKS.