Figure 4.

T4P in Acidovorax citrulli, causal agent of bacterial fruit blotch and seedling blight of cucurbit plants. (A) Transmission electron microscopy of wild-type strain M6 following growth for 48 h on nutrient agar (NA) plates. Solid and dashed arrows indicate T4P and polar flagellum (PF), respectively (bar = 0.5 μm); (B) Typical twitching halos surrounding bulk colonies of strain M6 after 96 h of growth on NA; seen by the naked eye; (C) Twitching halos seen around colonies of strain W1 by light microscopy after 96 h of growth on NA; (D) Halos are not detected around colonies of a W1 pilA mutant (strain W1-A; lacking T4P and twitching motility) grown under similar conditions as described for W1 in C; (E) Effects of T4P deficiency on virulence of A. citrulli, assessed by seed-transmission assays with melon cv. Ophir. Seeds were incubated with the different strains (at 10⁶ cfu/mL), and sowed in pots containing sand that were kept in a greenhouse at 25–28 °C. Pictures were taken 8 days after sowing. M6, wild type; M6-M, pilM mutant; M6-T, pilT mutant; control, seedlings from non-inoculated seeds. Figure composed from figures published by Bahar and colleagues [37].