Figure 5

RB50Δ sigE is less cytotoxic to macrophages than RB50. RAW 264.7 cells were incubated at an MOI of 10 with medium containing RB50 pEV, RB50ΔsigE pEV, RB50ΔsigE pSigE, TTSS-deficient RB50 strain WD3, or medium alone for 4 hours in the presence of 1 mM IPTG to induce expression of sigE from the pLac promoter of pSigE. The average percent cytotoxicity of four wells in four separate experiments as measured by (LDH release from a well/LDH release from the positive control well) x100 ± SE is shown. The differences in percent cytotoxicity between RB50ΔsigE pEV and either RB50 pEV or RB50ΔsigE pSigE are statistically significant (** indicates P value < 0.01), while the cytotoxicities of RB50 pEV and RB50ΔsigE pSigE are not significantly different.