Cells expressing CFP under the control of the comGA promoter. wt, phage-cured strain EGDe; +sigH, the wt strain overexpressing sigH; +sigH+comK, the wt strain overexpressing sigH and comK; RN+sigH, S. aureus RN overexpressing L. monocytogenes
sigH. Data represent the averages with SDs from 3 independent experiments. Significant differences are indicated. *, P = 0.002; **, P = 0.00001. ND, none detected. The sampling point is shown in Fig. 2.