A bacterial culture (200 l containing 1.8 * 109 cells) was treated with an antibiotic Z (50 μg per ml) for 4 h at 37ËšC. After this treatment, the culture was divided into two equal aliquots. Set A: 100 μl was plated on Luria agar. Set B: 100 μl was centrifuged, the cell pellet washed and plated on Luria agar. After incubating these two plates for 24 h at 37ËšC, Set A plate showed no colonies, whereas the
Set B plate showed 0.9 * 109 cells. This experiment showed that the antibiotic Z is