Figure 1. Effects of UV irradiation and NQO exposure on DNA content in wild-type and recombination-defective cells.
The DNA content of cells treated with either NQO (10μM) or irradiated with UV light (40J/m2) was analyzed using flow cytometry of propidium iodide stained cells (see Section 2.3). Approximately 50,000 cells were analyzed and cell count is plotted against relative fluorescent intensity(in arbitrary units). E. coli strain P90C is the parent strain of FC40 and its derivatives used in this study (Table 1). (A) UV irradiation and NQO treatment have different effects on the DNA content in recombination competent cells. (B) Both UV irradiation and NQO treatment reduce the DNA content and broaden the fluorescent peaks in cells defective for recombination.