Fig 4.
The GADi system is able to confer increased acid tolerance in the absence of any extracellular Glt. The GAD system is able to function solely on intracellular Glt, and the strains that accumulate higher GABAi demonstrate the highest acid tolerance. (A) Acid resistance of wild-type LO28 and its ΔgadD1, ΔgadD2, and ΔgadD1D2 isogenic mutants in DM (−Glt) at pH 3. (B) Accumulation of GABAi in wild-type LO28 and its ΔgadD1, ΔgadD2, and ΔgadD1D2 isogenic mutants in DM (−Glt) at pH 4. (C and D) Acid resistance (C) and GABAi accumulation (D) of wild-type LO28 and its isogenic mutants were measured in BHI at pH 3 and pH 4, respectively. Markers represent an average of measurements performed in triplicate, and error bars represent the standard deviation.