Figure 1. Surface colonization of Medicago roots by cocktails of the enteric pathogens S. enterica and E. coli O157:H7 and their growth in root exudates.

Confocal laser-scanning microscopic image of Medicago roots that were colonized with cocktails of S. enterica (A) or E. coli O157:H7 (B) containing GFP as the reporter. The plants were inoculated with 1×10⁴ CFU/plant, and 10 days post-inoculation the roots were fixed with 4% paraformaldehyde and observed under the microscope. Scale bars represent 100 µm. (C) The growth of S. enterica and E. coli O157:H7 cocktails in Luria-Bertani (LB) and Fåhraeus medium at 25°C for 72 hours. The normal growth of these strains was observed in LB medium, whereas no growth was detected in Fåhraeus medium. (D) The growth of cocktails of S. enterica and E. coli O157:H7 in 2-week-old root exudates (RE) of Medicago. Both of these cocktails grew in the 2-week-old root exudates.