FIG 1.

Colonization of mice with E. coli strain MP1. (A) Schematic of the colonization protocol. Mice were fed streptomycin (Strep.) in their drinking water for 72 h. The water with streptomycin was then removed and replaced with antibiotic-free water, and there was no further antibiotic treatment. After an additional 24 h, mice were orally inoculated with approximately 10⁹ CFU of E. coli cells by gavage. (B) Circles show data for 16 mice colonized with MP7, an mcherry-marked MP1 derivative (MP1 att_λ::pML8). CFU were measured on the indicated days following inoculation. Triangles show measurements of total E. coli (Lac⁺ colonies on MacConkey plates) for three mice that were not treated with streptomycin and were not exposed to MP1. (C) Colonies of MP7 and MP13, a gfp-marked MP1 derivative (MP1 att_λ::pAS07). The image is an overlay of red and green fluorescence images of colonies growing on LB agar containing 15 μg/ml tetracycline.