FIG. 2.

Temporal expression of genes required for formation of the rdar morphotype in serovar Typhimurium. Expression of agfD, agfB, adrA, or RpoS (σ³⁸)-responsive promoter::lux fusions during ATCC 14028 growth in 1% tryptone at 28°C with agitation. A. Light production as a function of time. Luminescence (counts per second [cps]) measurements for agfD and agfB::lux fusions are on the left axis; measurements for adrA and RpoS-responsive lux fusions are on the right axis. Representative expression curves from one experiment are shown. The inset shows cell density measurements (A₆₂₀) for each reporter strain as a function of time. B. Light production of lux reporter strains as a function of time, normalized by the maximum cps of each strain. To ensure accurate timing of expression during growth, each assay was repeated at least six times and individual growth curves were matched. The expression curves represent the average from these experiments. C. Expression curves from panel B were enlarged to highlight the temporal resolution of gene expression. The line is representative of the 10% gene activation level.