Figure 3. Toxicity of phenazine-1-carboxylic acid is pH dependent.

Nematode death after exposure to 100 µg/mL of phenazine-1-carboxylic acid or 1-hydroxyphenazine in PGS agar plates buffered at pH 4 (50 mM sodium acetate), 5 (50 mM sodium citrate), 6 (50 mM potassium phosphate), 7 (50 mM potassium phosphate), or 8 (50 mM potassium phosphate). There is no observable killing by phenazine-1-carboxylic acid at pH 6, 7, or 8, or by DMSO without phenazines under any of the buffer conditions.