Biochemistry, Microbiology & Molecular Biology

A bacterial culture (200 l containing 1.8 × 109 cells) was treated with an antibiotic Z (50 g per ml) for 4 h at 37˚C. After this treatment, the culture was divided into two equal aliquots. Set A: 100 l was plated on Luria agar. Set B: 100 l was centrifuged, the cell pellet washed and plated on Luria agar. After incubating these two plates for 24 h at 37˚C, Set A plate showed no colonies, whereas the Set B plate showed 0.9 × 109 cells. This experiment showed that the antibiotic Z is (A) bacteriostatic (B) bacteriocidal (C) bacteriolytic (D) apoptotic Common Data Questions Common Data for Questions 48 and 49 : In a muscle, the extracellular and intracellular concentrations of Na + are 150 mM and 12 mM, and those of K+ are 2.7 mM and 140 mM, respectively. Assume that the temperature is 25 oC and that the membrane potential is -60 mV, with the interior more negatively charged than the exterior. (R = 8.314 J mol -1 K-1; F = 96.45 kJ mol-1 V-1)