Comparison of different Y. pseudotuberculosis strains for survival inside macrophages as determined by fluorescence microcopy.

BMDMs were infected with the indicated GFP-encoding strains at an MOI of 10, as described in Figure 1. At 1 h, 4 h and 23 h post infection, the infected BMDMs were fixed and analyzed by fluorescence microscopy. One hour before fixation, IPTG was added to induce de novo expression of GFP from viable intracellular bacteria. Shown are GFP or an overlay of GFP and phase contrast signal from representative images.