FIGURE 1.

Characteristics of the plating defect of ΔoxyR and ΔkatB on LB plates. (A) Spotting assay. Cells grown to the mid-log phase (OD₆₀₀ of ∼0.4) were regarded as undiluted (dilution factor 0, ∼10⁸ CFU/ml) and were subjected to 10-fold series dilution. Five microliters of each dilution was dropped on LB plates. WT, the wild-type; Vec, empty vector. (B) Morphological observation under microscope. Cells of indicated strains at mid-log were spotted on slide with LB agar as described in the Materials and Methods. Pictures were captured at indicated times. The ΔarcA strain was incubated with 0.5 mM SDS. (C) Effects of catalase on rescuing viability of ΔoxyR and ΔkatB. Catalase (2,000 U) was applied to the drops at the indicated times. Experiments were performed at least three times, and representative results were shown.