FIG. 2.

Cytotoxicity of M. pneumoniae toward HeLa cell cultures. (A) Infection assay with the M. pneumoniae prkC::Tn strain GPM11 and the prpC::Tn strain GPM68. HeLa cell culture without M. pneumoniae (left top; control); HeLa cell culture incubated with wild-type M. pneumoniae (right top; wt); HeLa cell culture incubated with the prkC or prpC mutant (bottom; prkC::Tn or prpC::Tn, respectively). After 6 days, HeLa cell cultures were stained with crystal violet and photographed. Scale bar, 0.1 mm. (B) Quantification of HeLa cells after infection with wild-type M. pneumoniae or the prkC or prpC mutant. The cell count of surviving cells is indicated as the number of viable cells per field of view, quantified by crystal violet staining after 6 days of incubation. An uninfected HeLa cell culture served as a control. Error bars indicate the standard deviation (based on three independent experiments).