FIG 2.

Phenotypes of c-di-GMP-free mutant 15ΔDGC. (A) Swimming motility. (B) Swarming motility. (C) Biofilm formation in SOB plus 1% sucrose (SOBS) medium. *, P < 0.001 (by Student’s t test) (n ≥ 3 independent experiments). (D) Virulence assay on rice seed germination. Seven dilution gradients of bacterial cultures were cocultured with 15 rice seeds at room temperature for 6 h before being washed with sterilized water, and rice seeds were then germinated at 28°C under 16 h of light and 8 h of dark for 1 week. *, P < 0.001; ns, not significant (P > 0.05) (by two-way analysis of variance [ANOVA] with multiple comparisons) (n ≥ 3 independent experiments). (E) Fluorescence inverted microscopy observation of colonization. Rice seeds were incubated with strain EC1 and mutant 15ΔDGC carrying a plasmid expressing GFP for 6 h and transferred to moistened filter papers at 28°C for 40 h before fluorescence microscope observation. Bars = 500 μm.