Fig. 2

Live/dead staining was performed with fluorescein diacetate (FDA) and propidium iodide (PI) for pool 5 (P5) and pool 20 (P20). Viable cells were able to convert nonfluorescent FDA into the green fluorescent metabolite fluorescein because of esterase-dependent conversion (A, B). The nuclei staining dye PI (red) was able to pass through dead cell membranes and intercalate with the cell’s DNA double helix (C, D). An overlay of both (E, F) after 72 h of growth at 41 °C is exemplarily shown. For every pool, 30 pictures were analyzed (Nikon Microphot-SA microscope, Nikon Corporation, Tokyo, Japan; Cell^F, Olympus Corporation, Tokyo, Japan)