FIG 5.

Arginine catabolism protection can occur by a pH-dependent mechanism and a pH-independent mechanism. (A) Wild-type bacteria (circles) and the ΔArcC (squares), and ΔArcD (triangles) mutants were cultured in THY medium supplemented with various concentrations of arginine for a 6-day period. Following the 6-day period, the viability of the cultures was measured as previously described. (B) The remaining culture was then filtered sterilized, and the pH was measured using a pH probe. (C) The relationships between viability and pH were investigated by replotting the data presented in panels A and B. The data displayed are the mean and standard deviation of recovered CFU from culture pH values of between 5.0 and 6.0 from at least three independent experiments. The level of detection (L.O.D.) was 33 CFU.