Fig 7. AauR is required for glutamate-dependent growth, T3SS deployment and virulence of the bean pathogen P. syringae pv. syringae B278a.

(A) Growth of wild type B728a and B728a ΔaauR in M9 minimal medium supplemented with 10 mM glutamate as the sole carbon and nitrogen source. Cultures were inoculated at an optical density at λ = 600 nm (OD₆₀₀) of 0.1 and grown for 24 hours at 28°C within a 96-well plate. Graphed are means ± SD of OD₆₀₀ readings taken at 30 min intervals, n = 3. (B) GFP fluorescence of B728a and B728a ΔaauR strains carrying hrpL_promoter:gfp reporter plasmids. Bacteria were incubated in a minimal medium (MM) with 10 mM fructose (fru) or 10 mM fructose and 200 μM aspartate (asp) for 6 hours. Graphed are means ± SE of GFP fluorescence normalized to OD₆₀₀ and background fluorescence from empty vector strains; n = 3. (C) Leaves of 14-day-old bean plants were syringe-infiltrated with 1 x 10⁴ cfu/mL of B728a. Bacterial populations in infected leaves 0 and 3 days post-infection. Graphed are log-transformed means ± SE of colony-forming units (cfus) in infected leaf tissue, n = 4. Data in all panels are representative of results from three independent experiments. Asterisks denote significant differences based on t-test. ** is P < 0.05, *** is P < 0.01 and ns is not significant at α = 0.05.