Figure 4. AlsSD activity counters cytoplasmic acidification.

(A) Over-expression of AlsS rescues pyruvate-mediated growth inhibition of ΔalsSD mutant. (B) Intracellular pH (pHi) of UAMS-1 and derivatives following pyruvate stress. Bacterial cells loaded with the pH sensitive dye, cFSE, were suspended in potassium phosphate buffer (pH 4.5) and their pHi was measured as a function of the fluorescence emitted, either in the absence or presence of 40 mM sodium pyruvate (indicated by black arrow). (C) The rates of pHi recovery in each strain were measured from the slopes of the primary rise in pH_i traces represented in panel B, (Statistical significance was assessed using one way ANOVA followed by Newman Kewl's multiple post-comparison test, n = 3; ** P<0.005, *** P<0.0005).