Examination of the σ^E (RpoE) levels from different genetic backgrounds and cell fractions.

σ^E was detected by Western blots from protein samples obtained from whole cells (A), soluble (B, periplasm and cytoplasm) and insoluble (C, membranes) fractions. TolC-specific and σ^E-specific antibodies were used in (A), while antibodies raised against σ^E and a MalE-TolC fusion protein were used in (B) and (C). The MalE-TolC fusion antibodies were used to verify the purity of soluble (MalE) and insoluble or membrane (TolC) fractions. Relevant genotypes of the strains are shown at the top.