The Δ flgA mutant displayed slow pellicle formation. (A) Swimming and swarming motility assays of the ΔflgA mutant. In both panels, the ΔflgA mutant (Upper) was compared to the WT (Lower). The ΔflgA* strain refers to the ΔflgA mutant containing pBBR-FLGA. (B) Electron micrographs of WT and the ΔflgA mutant. No flagellum was observed on the mutant. (C) Left panel, pellicle formation of the ΔflgA mutant. Right panel, the cell densities of cells in pellicles of the WT and the ΔflgA mutant. The WT, dark red; the ΔflgA mutant, light blue. E represents the time at which the cell density of ΔflgA mutant catches up (10 days after inoculation in the experiment). Presented are averages of four replicates with the standard deviation indicated by error bars.