Figure 3.

Colicinogenic plasmids identified in CRE isolates are active in vitro. (A) MDR_006 kills other E. coli bacteria. MDR_006 was spotted onto LB agar (at 0.8% w/v) without or with mitomycin C (at a final concentration of 0.1 μg mL⁻¹) next to the E. coli K-12 strain BW25113,²² with each strain at a different dilution (1 vs 10⁻⁴, respectively). Plates were incubated at 37 °C overnight. The left image shows a schematic representation of the competition conditions. (B) pCol006 harbored by MDR006 encodes a Colicin E1-like toxin. LB agar (at 1.5% w/v) plates were swabbed with E. coli BW25113, its btuB or tsx mutant (as obtained from the Keio collection),²² and four wells were carved into each plate. Wells were filled with culture supernatant (spent media) either produced by MDR_006 or by E. coli BW25113 after overnight growth in the presence of 0.1 μg mL⁻¹ mitomycin C. This panel contains a schematic representation of the growth inhibition assay (left; top), representative images of the obtained growth inhibition zones for all strain-spent media combinations (left; bottom), and quantification of the growth inhibition zones (right). (C) MDR_119 releases cloacin toxin when it is exposed to DNA damage. The panel shows an SDS-PAGE analysis of TCA-precipitated culture supernatants of MDR_119 after overnight growth in the absence (lane 1) or presence (lane 2) of mitomycin C (at a final concentration of 0.5 μg mL⁻¹). Molecular weight markers (M) are on the left, the red arrow indicates the position of the bands originating from the cloacin toxin.