FIG 5.

Increasing the osmotic pressure can partially substitute for cations in supporting the ability of YqjA to permit growth at elevated pH. (A) A ΔyqjA mutant harboring pBADyqjA was grown to mid-log phase at pH 7.0 and then inoculated into salt-free liquid LB-Amp medium at pH 9.25 containing 0 mM, 100 mM, 200 mM, or 300 mM sucrose, and growth was monitored. (B) Comparison of growth rates between ΔyqjA harboring pBADyqjA in salt-free LB-Amp medium, salt-free LB-Amp medium containing 300 mM sucrose, and LB-Amp medium containing 150 mM NaCl. (C and D) A ΔyqjA mutant harboring the control vector pBAD or pBADyqjA was grown to mid-log phase at pH 7.0, and then 5 μl of serially diluted cells was spotted onto LB-Amp medium plates at pH 9.25 containing 100, 200, or 300 mM sucrose (C) or 300 mM mannitol, 300 mM sorbitol, or 150 mM choline chloride (D). The plates were incubated at 37°C for 20 to 24 h. The error bars indicate standard deviations of three independent measurements.