FIG. 7.

Intracellular expression of htrA. β-Galactosidase activity, measured by hydrolysis of the fluorescence substrate FDG, resulting from the expression of lacZ driven by the htrA promoter during the intracellular infection of macrophages and A. polyphaga and compared to bacteria grown in BYE. Background fluorescence in arbitrary units per CFU generated by a promoterless lacZ construct was subtracted at each time point. The values shown are the ratios of the fluorescence units of intracellular bacteria to those in in vitro-grown bacteria incubated in tissue culture medium. The absence of error bars indicates error values too small to be shown. At least two independent experiments, in duplicate, were performed.