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Figure 4: OMV-mediated macrophage cytotoxicity is SOS dependant. OMVs isolated from the wild-type (wt) and the LexA noncleavable (lexAN) cells as indicated were incubated with macrophage. Top: phase-contrast microscopy of macrophage incubated with OMVs at 1.3 μg/mL after a 1 hr incubation. Bar, 20 μm. Bottom: cytotoxicity was measured as the levels of released cytosolic lactate dehydrogenase after 4 hr incubation. It was set 0 for the macrophage-only control. OMV concentrations: grey, 1.3 μg/mL; doted, 0.65 μg/mL; blank, 0.325 μg/mL. (* 𝑃 < 0 . 0 5 , 𝑛 = 4 ) .