FIG 3.
The HetR binding site present in the trpE promoter is required for proper expression. Shown are bright-field (top), GFP fluorescence (middle), and chlorophyll autofluorescence (bottom) micrographs of the wild type (WT) bearing PtrpE-gfp in pPJAV381 (A) or PtrpE(mut)-gfp with a mutated HetR binding site in pPJAV382 (B). Fluorescence was quantified in the wild type and the ΔhetR (UHM103) and ΔtrpE (UHM335) mutants bearing pPJAV381 (green bars) or pPJAV382 (red bars) grown in the presence of nitrate (solid bars) or 24 h after the removal of combined nitrogen (hatched bars). All fluorescence measurements were taken at an OD750 of 0.1. Error bars represent standard deviations.