FIG 3.
Cytotoxicity of LAC assessed using established cell lines. MC3T3-E1 or RAW 264.7 cells were exposed to CM from cultures of LAC, its sarA mutant (ΔsarA), and its complemented sarA mutant (ΔsarAC). Viability was assessed after 24 h using Invitrogen Live calcein-AM staining (top) or fluorescence microscopy (bottom). The results of calcein-AM staining are reported as the average mean fluorescence intensity (MFI) ± standard deviation. *, statistical significance compared to the results observed with the isogenic parent strain; **, statistical significance compared to the results observed with the isogenic sarA mutant. DMEM, Dulbecco modified Eagle medium.