Subcellular localization of σF. Immunoblot assays performed with membrane and soluble fractions obtained from parental strain NA1000 (WT) and a CC3252 mutant with both cysteine residues C131 and C181 replaced for serine (C131-181S). Aliquots were taken immediately before or after cells were treated with 55μM potassium dichromate (K2Cr2O7) for 30min. Membrane and soluble fractions were obtained as described in Methods. Blots were developed using anti-σFantiserum and fluorescent CF680 Goat Anti-Rabbit IgG. σF is shown by an arrow.