Figure 2

Microtiter plate with three E. coli strains to demonstrate differential resazurin color change post X-irradiation. Wells containing 50 μl of cell suspension at 6.4 × 10⁷ colony-forming units per ml were irradiated with 250 Gy, 160 μl of LB/resazurin solution were added to each well and plates were incubated at 37°C for 4.5 h. Columns 1, 4, 7, and 10 contained strain SR1252 (polA, higher radiation sensitivity) cells; columns 2, 5, 8, and 11 contained strain SR1553 (recN, intermediate radiation sensitivity); columns 3, 6, 9, and 12 contained strain SR749 (parental, control strain, lower radiation sensitivity).