Effect of Hfq on virulence-related functions in E. amylovora. (A) Amylovoran production of E. amylovora Ea1189, Ea1189Δhfq, Ea1189Δhfq/pMLhfq, and Ea1189Δams. Bacterial strains were cultured in MBMA medium for 2 days, and the amount of amylovoran produced was quantified using the cetylpyrimidinium chloride (CPC) assay. (B) Swarming motility of Ea1189, Ea1189Δhfq, and Ea1189Δhfq/pMLhfq. Bacterial strains were inoculated at the center of swarming agar plates (0.3% agar), and the swarming diameters were measured at 18 h postinoculation. Asterisks indicate significant differences (P < 0.05) compared to Ea1189. (C) Relative amount of amsG, amsK, and fliC mRNA in Ea1189, Ea1189Δhfq, and Ea1189Δhfq/pMLhfq compared to Ea1189, measured by qRT-PCR. (D) Biofilm formation of Ea1189, Ea1189Δhfq, Ea1189Δhfq/pMLhfq, and Ea1189Δams. Bacterial strains were incubated with glass coverslips in static cultures of 0.5× LB broth. The biofilm formed on the coverslips was stained with crystal violet and quantified by measuring light absorbance at OD600. Asterisks indicate significant differences (P < 0.05) compared to Ea1189.