ATPase activity was higher in glycerol fermented wild type cells at pH 7.5
compared to pH 6.5 and pH 5.5; DCCD inhibited markedly ATPase activity at pH 7.5. The ATPase activity
at pH 7.5, compared with wild type, was lower in selC and less in hypF single mutants, suppressed in hyaB
hybC selC triple mutant. Moreover, total ATPase activity of mixed carbon fermented wild type cells was
maximal at pH 7.5 and lowered at pH 5.5. The ATPase activities of hypF and hyaB hybC selC mutants were
higher at pH 5.5, compared with wild type; DCCD inhibited markedly ATPase activity of hypF mutant.
These results demonstrate that in E. coli during glycerol fermentation the membrane
proton-translocating FOF1-ATPase has major input in overall ATPase activity and alkaline pH is more optimal
for the FOF1-ATPase operation. Hyd-1 and Hyd-2 are required for the FOF1-ATPase activity upon
anaerobic fermentation of glycerol. The impact of Hyd-1 and Hyd-2 on the FOF1-ATPase is more obvious
during mixed carbon fermentation at slightly acidic pH.