Figure 6

Effects of cadBA mutations on cellular infection and replication. A Invasion of HeLa cells by E. tarda. HeLa cells were infected with the same dose of E. tarda TX01, TX01ΔcadA, TX01ΔcadB, TX01ΔcadBA, TX01ΔcadAC and TX01ΔcadBC strains for 1 and 2 h, and washed with PBS. Then, HeLa cells were lysed and the CFU were counted. B Replication of E. tarda in macrophages. The murine macrophage cell line RAW264.7 was infected with E. tarda and mutants above mentioned for 2 h, followed by treatment with gentamicin for 2 h to kill extracellular bacteria. After being washed with PBS, the cells were incubated for the time intervals indicated. Then, the cells were lysed and the CFU were counted. Data are the means of three independent experiments and presented as means ± SEM (N = 3). N, the number of times the experiment was performed. **, P < 0.01; *, P < 0.05. C, TX01, TX01ΔcadA, TX01ΔcadB and TX01ΔcadBA containing pGFPuv plasmid were used to infect RAW264.7 cells for 0, 2 and 4 h. DNA was stained blue by DAPI, the cells were observed by confocal microscopy.