Fig. 5.

Depletion of the Kan^r gene makes the SPH136 mutant sensitive to kanamycin. SPH136 cell cultures were grown in C medium containing 2 μM ComS* until they reached an OD₄₉₂ of 0.3. Then, they were pelleted, washed once, and resuspended to an OD₄₉₂ of 0.05 in ComS*-free C medium containing kanamycin (400 μg ml⁻¹). The resuspended cells were 2-fold diluted in the same medium in a 96-well plate and incubated in a Fluostar Optima luminometer at 37°C for 16 h. Growth (measured as the OD₄₉₂) was determined automatically by the luminometer at 10-min intervals. As Kan^r was depleted over time, the growth rate of the SPH136 cells gradually slowed down. After being cultivated for about 8 h in ComS*-free medium, their growth was completely inhibited by kanamycin.