Figure 1. Deletion of mgrB leads to up-regulation of multiple genes in the PhoQ/PhoP Regulon.
(A) YFP (left) and CFP (right) fluorescence images of a transcriptional reporter strain with deletions of various PhoP-regulated genes, growing on LB agar. The strain contains a chromosomal copy of the PhoP-regulated mgrB promoter (PmgrB) driving yfp expression and a constitutive promoter driving cfp expression as an internal reference. The specific strains are, clockwise starting with WT, TIM92, TIM100, AML4, AML6, AML8, AML16, AML10, AML12, and AML14. (B) Fluorescence of several strains (as in A) grown in liquid. (C) Fluorescence of phoPQ transcriptional reporters grown in liquid. The strains are, from left to right, TIM148, TIM229, AML22, and AML23. (D) Fluorescence of mgtA transcriptional reporters grown in liquid. The strains are, from left to right TIM91, TIM99, AML24, AML25. For liquid cultures, cells were grown in minimal glucose medium with 100 µM (white) or 10 mM (black) MgSO4 and cellular fluorescence was measured by microscopy and image analysis as described in Materials and Methods. The error bars represent the range of means for two independent cultures.