Phenotypes of MB35 cells, LpCSfo cells, and LpCSfoHR cells. (a) These cells were grown in PS medium with (+Tet) or without (-Tet) teteracyclin. Membrane potential of mitochondria was visualized by staining of cells with MitoTracker Orange, as described in the legend of Figure 2. As was expected, the staining of mitochondria was almost completely vanished in LpCSfo cells grown without Tet, because their mtDNA with an intact Sfo I site would be cleaved by Sfo I eventually to become a ρ0 state. Bars, 20 μm. (b) Development of starved MB35 cells and LpCSfoHR cells on agar. MB35 cells and LpCSfoHR cells grown with (+Tet) or without (-Tet) tetracycline were washed twice in BSS and plated on 1.5% non-nutrient agar at a density of 5 × 106 cells/cm2. This was followed by incubation for the indicated times at 22°C. Bars, 0.5 mm.