Sinorhizobium meliloti Sigma Factors RpoE1 and RpoE4 Are Activated in Stationary Phase in Response to Sulfite
Figure 5
Expression of rpoE1 and rpoE4 at different growth phases and in various genetic backgrounds.
Expression from the promoter of the rpoE1 (A, C) or rpoE4 (B, D) operon was estimated by measuring β-galactosidase activity driven from the chromosomal PrpoE1-lacZ fusion in strains CBT1183 (wt), CBT1185 (ΔrpoE1), CBT1191 (ΔrpoE4), (CBT1247 (ΔrpoE1 ΔrpoE4), CBT1315 (ΔsorT), CBT1350 (ΔsorT ΔrpoE1), CBT1354 (ΔsorT ΔrpoE4) and CBT1358 (ΔsorT ΔrpoE1 ΔrpoE4) or from the chromosomal PrpoE4-lacZ fusion in strains CBT1218 (wt), CBT1220 (ΔrpoE1), CBT1224 (ΔrpoE4), CBT1251 (ΔrpoE1 ΔrpoE4), CBT1317 (ΔsorT), CBT1356 (ΔsorT ΔrpoE4), CBT1352 (ΔsorT ΔrpoE1) and CBT1360 (ΔsorT ΔrpoE1 ΔrpoE4) grown in Vincent minimal medium with sodium succinate as carbon source either to exponential phase (OD600∼0.5; white bars) or stationary phase (∼24–30 h after the previous point; grey bars). The results shown are the means and standard errors of data from four to thirteen independent experiments.