The hfq gene is responsible for RBA. (A) Mobility-shift assay of the ompA mRNA-binding activity of MC4100 strain (hfq+), its derivatives AM111 (hfq1) and AM112 (hfq2), and hfq1 strain provided with the plasmid pHFQ607, containing the hfq gene. Cells were grown in Mops-acetate medium, and 10 μg of S30 extracts were used for the RNA–protein complex formation. (B) Western blot analysis of the same extracts as in A tested with Hfq-specific antibodies, as described in Materials and Methods.