Figure 2

Transcription of the cacA gene is activated by RpoS but repressed by RssB. A. β-galactosidase activity from a PcacA-lac transcriptional fusion 1 in the wild-type (−; AK1056), ΔcpxR mutant (AK1063), phoP mutant (AK1064), ΔrssB mutant (AK1065), and ΔrpoS mutant (AK1066) strains. Bacteria were grown for 4 h in LB before β-galactosidase activity was measured (Miller units). The data correspond to the means of two independent experiments performed in duplicate, and the error bars represent standard deviations. B. β-galactosidase activity from PcacA-lac transcriptional fusion 1 or 2 in a wild-type strain (−; AK1056 or AK1067) and a ΔrpoS mutant strain (AK1059 or AK1071). Note that the PcacA-lac 1 strain contains a DNA fragment encompassing the 3’ region (80 bp) of STM1851 and the intergenic region (110 bp) between STM1851 and cacA, whereas the PcacA-lac 2 strain harbors only the intergenic region (110 bp) between STM1851 and cacA preceding the lacZ gene (See Methods). Bacteria were grown for 4 h in LB before β-galactosidase activity was measured (arbitrary units) as described [42]. The data correspond to the means of three independent experiments performed in duplicate, and the error bars represent standard deviations. The data in the panels A and B were obtained using two different methods.