Effect of EIPA and CCCP on swimming of B. subtilis expressing wild-type BCI-AB or mutant B. clausii stators. (A) Multiple alignment of the region containing the single transmembrane segment of Oceanobacillus iheyensis MotB (OI_MotB) and MotS (OI_MotS), B. subtilis MotB (BS_MotB), MotS (BS_MotS), and B. clausii MotB (BClMotB). The sequence of B. clausii MotB is highlighted in yellow. The red letters show locations of point mutations in B. clausii MotB mimicking BS_MotB to yield BClMotB-H. The blue letters show locations of point mutations in B. clausii MotB mimicking BS_MotS to yield BClMotB-Na. D26 is critical for flagellar rotation and is highlighted with violet (2). (B) The swimming speeds of strains BCl-AB (filled triangles) and BCl-AB-H (filled circles) were measured in TY/20 medium [pH 9.0 (Left) and pH 9.5 (Right)] at various concentrations of sodium. (C) Effect of EIPA and CCCP on swimming speeds of strains BCl-AB (filled triangles) and BCl-AB-H (filled circles). The swimming speeds were measured in TY medium (pH 9.5, 63 mM Na+) at various concentrations of EIPA (Left) or CCCP (Right). (D) The swimming speeds of strains BCl-AB (filled triangles) and BCl-AB-Na (filled circles) were measured in TY/20 medium [pH 8.5 (Left) and pH 9.0 (Right)] at various concentrations of sodium. (E) Effect of EIPA and CCCP on the swimming speeds of strains BCl-AB (filled triangles) and BCl-AB-Na (filled circles). The swimming speeds were measured in TY medium (pH 8.5, 63 mM Na+) at various concentrations of EIPA (Left) or CCCP (Right).