FIGURE 1.

Western blot analysis of wild-type cells, the ΔearA strain and a spontaneous mutant of the ΔearA strain, ΔearA-sp, in which the expression of FlaB2 was restored. (A) Wild-type cells (Mm900) produce FlaB2 readily detected in western blots using FlaB2-specific antibodies. In the ΔearA strain, where the gene encoding the transcriptional activator EarA required for the transcription of the fla operon has been deleted, no FlaB2 was detected. (B) In the spontaneous mutant ΔearA-sp, the expression of FlaB2 was restored. (C) Confirmation of the deletion of earA in ΔearA-sp and Δ3A mutants. PCR products obtained using ΔearA, ΔearA-sp and Δ3A mutant cells as templates with primers amplifying the flanking area of the earA gene were smaller than those obtained using wild-type and ΔflaB2 cells as template with the same primer pair, confirming that earA was deleted in the ΔearA-sp and Δ3A mutants.