Figure 1. Hfq/DsrA requirement at 24 °C and 37 °C. The steady-state levels of RpoS were determined by quantitative western blotting in the E. coli hfq^- strain JW4130 harboring the control plasmid pACYC184 (lanes 1 and 3) and plasmid pAHfq, encoding Hfq (lanes 2 and 4), respectively. The strains were grown to early log phase (OD₆₀₀ of 0.4) at 24 °C (lanes 1 and 2) or 37 °C (lanes 3 and 4). Equal amounts of cellular protein were loaded onto the SDS-polyacrylamide gel. Immunodetection of RpoS, ribosomal protein L14 (loading control), and Hfq as well as the detection of DsrA and 5S rRNA (loading control) by northern blot analysis was performed as described in the Materials and Methods. Only the relevant parts of the immunoblots and the autoradiographs are shown.