FIG. 5.

PLA secretion by wild-type and pilD mutant L. pneumophila. In two trials (I and II), supernatants from 130b (black column) and NU243 (white column) late-log cultures were tested for their ability to release free fatty acid (FFA) from phosphatidylcholine as measured by the NEFA-C-Kit. The values presented are the mean and standard deviations from duplicate cultures. The differences between 130b and NU243 activity were significant (P < 0.01 and < 0.001 for I and II, respectively; Student's t test). Similar conclusions were obtained by using thin-layer chromatography.