Fig 2. Mutations affecting the hilD message secondary structure alter invasion gene expression.

(A) Expression of the invasion gene sipC was assessed in the mutants shown using a lacZY transcriptional reporter fusion by β-galactosidase assays. Histograms and error bars represent means ±SD (n = 3). (B) Expression of the invasion gene sopB was measured over time using a luxCDABE transcriptional reporter fusion (n = 5), assessing luminescence normalized to bacterial numbers (luminescence/OD₆₀₀). All strains differed from the wild type for (A) mean expression at P < 0.001, and (B) mean peak expression at P < 0.0001.