Figure 2. Endophytic colonization of Medicago roots by enteric pathogens (S. enterica and E. coli O157:H7).

Bacterial CFUs recovered from Medicago roots 10 days post-inoculation with cocktails of S. enterica (A) and E. coli O157:H7 (B). The mean value of 5 replicates is represented; error bars represent standard error of the mean. The CFU values were log₁₀ transformed. (Note: 2 ml of inoculum was used.) (C–E) Longitudinal sections of Medicago roots inoculated with enteric pathogens at 1×10⁴ cfu/plant. At 10 days post-inoculation, the roots were fixed with 4% paraformaldehyde, and sections were obtained using a Vibratome®. (C and E) Longitudinal sections of roots inoculated with the S. enterica cocktail. (C) Ep-Epidermis, OC-outer cortex, IC- inner cortex and Va-Vasculature. (D) Longitudinal section of roots inoculated with the E. coli O157:H7 cocktail. Note that both strains (E. coli O157:H7 expressing either DsRED or GFP as the visible marker) colonize the same region. Scale bar represents 50 µm for C and 10 µm for D and 20 µm for E.