Figure 3
Antimicrobial activity of SAGs. (A) Effect of SAGs on Clavibacter michiganensis viability expressed as the logarithm of colony forming units per ml (log CFU/ml) at different time-points. SAGs application (arrow) at a final concentration of 60 μg/ml on fresh C. michiganensis liquid culture (circles) in comparison to non-treated bacteria (squares) was shown. (B) Antimicrobial activity of SAGs determined as Minimal Inhibitory Concentration (MIC) in vitro against different bacterial and fungal phytopathogens evaluated in at least three independent experiments. (C) Effect of SAGs-treatment on lemon fruits inoculated with Penicillium digitatum. Disease incidence (% diseased fruits) and disease severity (fruit area affected by fungus) were evaluated in inoculated fruits either treated with water (IC), SAGs at inhibitory (200 μg/ml) and sub-inhibitory (100 μg/ml) concentrations of pathogen growth, and 500 ppm of commercial fungicide Imazalil, 10 fruits were tested for each treatment in six independent assays. Different letters indicate significant difference among treatments using the DGC test (p < 0.05). Pictures in the lower panel show disease symptoms on lemon fruits for each treatment. (D) Effect on membrane permeability of bacterial cells treated with 60 μg/ml SAGs (squares), Valinomycin (circles) and water (triangles) at time-points indicated, using the intracellular fluorescent diSC35. (E) Effect of SAGs (200 μg/ml) on membrane permeability of fungal mycelia cells at time-points indicated (circles) compared to water-treated cells (squares). Membrane leakage was determined by measuring relative conductivity of C. cassiicola mycelia. Results represent the average ± standard deviation of three independent experiments. (*) Denote statistically significant differences with control treatment.
