Identification of genes required for cytosolic survival of L. monocytogenes in macrophages. (A) Cleanly transduced L. monocytogenes bacteriolysis mutants (MOI of 10) were tested for bacteriolysis in iIFNAR−/− macrophages over a 6-h infection. All data are normalized to wild-type levels of bacteriolysis and presented as means ± standard errors of the mean (SEM) of results from five independent experiments. (B) Cleanly transduced L. monocytogenes bacteriolysis mutants were grown to the exponential or stationary phase in BHI media at 37°C and then examined for in vitro lysis. β-Galactosidase activities of supernatants are normalized to β-galactosidase activities of 100% lysed cultures, and data are presented as mean percent ± SEM of results from four independent experiments.