FIG. 1.

EMS resistance of wild-type and α⁻β⁻ spores with or without a recA mutation. Spores of various strains were incubated at an OD₆₀₀ of ∼1 and 37°C in 0.4 M KPO₄ (pH 7.0)–0.45 M EMS. At various times, aliquots were diluted ∼100-fold in 2.4 ml of 0.1 M Na₂S₂O₃ and then diluted further in 50 mM KPO₄ (pH 7)–0.1 M NaCl prior to analysis of viable counts on LB medium plates (4). Symbols: ○, PS832 (wild type); ▵, PS356 (α⁻β⁻); •, PS2318 (recA); ▴, PS2319 (α⁻β⁻ recA). Essentially identical results were obtained in a replicate experiment.