FIG. 4.
Sensitivity of mutant spores to stress. (A) Plating efficiency of 2-day-old normal and mutant spores exposed to 0.2% NP-40 nonionic detergent and seeded onto lawns of K. aerogenes. The results are representative of two independent trials. (B) One-day-old spores were incubated in the DNA dye DAPI in 88% glycerol for 1 to 2 h and photographed under phase contrast or epifluorescence illumination. (C) Autofluorescence of untreated spores in water, visualized in the fluorescein channel. The phase-contrast images of normal and mutant spores were similar when viewed directly in the microscope.