Figure 2: Hfq promotes expression of invasin and exerts opposite effects on expression of the regulatory genes rovA and ompR.
(a) Immunodetection of InvA in Y. enterocolitica strain JB580v and derivatives. Bacteria were grown for 6 h in LB at 27 °C. Upper panel shows the immunoblot and bottom panel shows part of the Coomassie blue-stained gel used as loading control. (v), vector pACYC184; (phfq), plasmid phfq. The invA mutant produces a truncated InvA protein. The relative signal for full-length InvA compared to the parental strain (which was set to 100%) is indicated. (b,c) Fluorescence of isogenic strains of JB580v carrying, in (b): plasmid pFX-invA (translational fusion of invA with gfp under the control of PinvA promoter), and in (c): plasmid pFX-1 (gfp under control of Plac promoter) or pFX-Plac-invA (invA 5′UTR and invA‘-’gfp fusion under control of Plac promoter). Bacteria were grown in LB for 4 h (log.) and 22 h (stat.) and fluorescence was measured by flow cytometry. Results are the MFI and standard deviation of three (b) or two (c) independent experiments, each with three independent cultures per strain. (d,e) Fluorescence of parental strain JB580v and its isogenic hfq mutant carrying translational fusions of rovA (d) and ompR (e) with gfp was measured by flow cytometry. Bacteria carrying a promoter-less gfp (on plasmid pFX-0) were used to measure background fluorescence. Results are the MFI of at least two independent experiments, each with three independent cultures per strain. Significance was calculated with Student’s unpaired t-test (***P ≤ 0.001; **P ≤ 0.01; ns, not significant, P > 0.05).
