Tested different loading dyes enabling to follow cell viability by fluorescence microscopy. The ON culture of M15[pRep4-pQE30::KR] was split in two different Erlenmeyers and incubated at 37°C, 300rpm. One of them was kept in the dark while the other was illuminated (I = ) for 2 hours to induce cell death. For both samples, 200 µL were pipetted, centrifuged, and incubated 15 min (37°C, 200 rpm) with 200µL of one of the following loading dyes : 5-100µM Diaminofluorescein, 500-5nM MitoTracker Green FM (M7514, Invitrogen, Carlsbad, NM, USA), XX SYBR Safe DNA gel stain (S33102, Invitrogen). Cells were subsequently washed in 200 µL PBS, mounted on a microscope slide and observed with the epifluorescence microscope available in our lab (FITC filter cube).