Fig. 3.

Cells of the nhe1⁻ mutant have lost K⁺ facilitation but have retained Ca²⁺ facilitation. (A) Motility parameters for parental control strain Ax2, the nhe1⁻ mutant, and the nhe1⁻/nhe1⁺ complemented control in the absence of chemoattractant either in 40 mM K⁺ solution or 20 mM Ca²⁺ solution. P values were obtained by Student's t test. Parameters are defined in Materials and Methods. (B) 2D-DIAS-generated stacked perimeter tracks of three representative Ax2, nhe1⁻, and nhe1⁻/nhe1⁺ cells in 40 mM K⁺ solution. Perimeters were drawn at 12-s intervals over a 10-min period. The final outline of the cell is color coded blue. (C) 2D-DIAS-generated stacked perimeter tracks of three representative Ax2, nhe1⁻, and nhe1⁻/nhe1⁺ cells in 20 mM Ca²⁺ solution with perimeters drawn as described for panel B. No. cells, the number of cells analyzed; Inst. vel., instantaneous velocity; % cells > 9 μm/min, the proportion of cells moving with average velocities > 9 μm/min; Dir. persist., directional persistence; ns, not significant.