Figure 1

The identification of a novel connector-like factor, CacA. A. β-galactosidase activity from a cpxP-lac transcriptional fusion expressed in the wild-type strain (AK1052) harboring pUC19, pUC19-R1, and pWN1. 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. A genetic map of the cacA (STM1852) locus in Salmonella. Each arrow indicates a gene and its orientation in the chromosome. The chromosomal location corresponding to the inserted DNA fragment of the pWN1 plasmid clone is indicated by a horizontal bar. C. β-galactosidase activity from cpxP-lac or spy-lac transcriptional fusions in a wild-type (AK1052 or AK1053) strain harboring pASK or pASK-cacA. Bacteria were grown for 2 h in LB in the presence of 0.2 μg/ml anhydrotetracycline (ATc) 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. D. β-galactosidase activity from a cpxP-lac transcriptional fusion in the wild-type strain (AK1052) harboring pBAD18 or pBAD18-cacA and the ΔcpxR mutant (AK1061) and ΔcpxA mutant (AK1062) strains harboring pBAD18-cacA. Bacteria were grown for 4 h in LB in the presence (+) or absence (−) of 5 mM L-arabinose 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 representstandardrepresent standard deviations. E. β-galactosidase activity from cpxP-lac or spy-lac transcriptional fusions in a wild-type strain (−; AK1052 or AK1053) and a ΔcacA mutant strain (AK1075 or AK1076). Bacteria were grown for 4 h in N-minimal medium, pH 7.7 with 10 μM Mg2+ 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. Single and double asterisks indicate p < 0.05 and p < 0.01, respectively, using an unpaired t test for analysis.