FIG. 7.

Inhibition of an early step in cell division abolishes the σ³²-dependent stress response in E. coli. (A) Steady-state levels of σ³², FtsZ, and σ⁷⁰ proteins in cells expressing DicF antisense RNA (+) and in control cells with the vector (c) or the uninduced plasmid (−) were compared by Western blotting. As a loading control, a section of the Coomassie-stained gel (Co) is shown. (B) The activities of the σ³²-dependent groESL promoter in SR6618 expressing DicF from plasmid pGZdicF to deplete FtsZ, compared to those in controls, are shown. ▴, pGZdicF induced with 70 μM IPTG; ▵, pGZdicF without IPTG; □, pGZ119EH (vector control) with 70 μM IPTG. (C) Inhibition of σ³² by DicF expression in asynchronously growing cells. MG1665 harboring pGZdicF or pGZ119EH (control) was inoculated to an OD₆₀₀ of 0.01 and grown to early-logarithmic phase (OD₆₀₀, ∼0.1). IPTG was added to induce DicF expression, and samples taken before (0) and after the addition of IPTG were analyzed by Western blotting.