An In Vivo Selection Identifies Listeria monocytogenes Genes Required to Sense the Intracellular Environment and Activate Virulence Factor Expression
Fig 5
Post-transcriptional activation of ActA.
(A) Plaque area as a percentage of wild type. (B) qPCR of L. monocytogenes transcripts during BMM infection. For panels A and B, data are the mean ± s.e.m. of at least three independent experiments. (C) Schematic of the actA region in the chromosome. Thin black arrows represent predicted transcription start sites [15]. (D) Schematic of the constitutive pH-actA strain. (E) In vitro abundance of ActA normalized to P60 was measured by immunoblot and plotted as a percentage of the pH-actA strain during broth growth. Data are the mean ± s.e.m. of at least three independent experiments. (F) Abundance of ActA normalized to P60 was measured during BMM infection by immunoblot and plotted as a percentage of the pH-actA strain four hours post-infection of BMMs. Data are the mean ± s.e.m. of at least three independent experiments. (G) Schematic of the actA1p-rfp reporter strain and the actA1p strain. (H) RFP fluorescence six hours post-infection of BMMs with the actA1p-rfp reporter strains. Data are the mean ± s.e.m. of at least three independent experiments. (I) Plaque area as a percentage of wild type. Data are the mean ± s.e.m. of at least three independent experiments. (J) Female CD-1 mice were infected with 105 CFU of each mutant. Spleens and livers were harvested 48 hours post-infection and CFU were quantified. The solid lines indicate the median, and data represent two pooled experiments totaling n = 10 mice per strain. In all panels, p values were calculated using a heteroscedastic Student’s t-test * p < 0.05; ** p < 0.01; *** p < 0.001; ns (not significant) p > 0.05.