FIG. 6.

Effect of Na⁺, Li⁺, or K⁺ on the expression of nhaA′-lacZ in V. cholerae SV2 NhaA⁻ fusion strain (A) and V. cholerae SV3 NhaA⁺ fusion strain (B) at t = 6 or 10 h. Bacteria were grown in NB-Tricine (pH 8.5) either without the addition of salt (control), with 120 mM NaCl, with 120 mM LiCl, or with 120 mM KCl. Multiple assays of several independent growth experiments were performed, and the standard deviations for each determination are denoted by the line above each bar.