Figure 3. Motility of B. pseudofirmus and B. alcalophilus in liquid medium.

B. pseudofirmus OF4 and B. alcalophilus cells in the logarithmic growth phase that were grown at 30°C in MYE medium (pH 10.5) and KMYE medium (pH 10.5), respectively, were harvested and resuspended in 30 mM Tris-HCl (pH 9.0) that contained 5 mM glucose and the indicated sodium (A), potassium (B) or rubidium (C) concentrations as described in the Materials and Methods section. The red line and red open circles show the data for the B. pseudofirmus OF4 strain, and the blue line and blue filled circles show the data for the B. alcalophilus strain. The swimming speed was determined as described in the Materials and Methods section. The results that are shown represent the averages of three independent experiments in each of which the swimming speeds of 20 independent cells as calculated in each experiment. The error bars indicate the standard deviations of the values.